![Blood sugar
From Wikipedia, the free encyclopedia
Blood sugar concentration, or glucose level, refers to the
amount of glucose present in the blood of a human or
animal. Normally, in mammals the blood glucose level is
maintained at a reference range between about 3.6 and 5.8
mM (mmol/l). It is tightly regulated as a part of metabolic
homeostasis.
Mean normal blood glucose levels in humans are about
90 mg/dl, equivalent to 5mM (mmol/l) (since the molecular
weight of glucose, C6H12O6, is about 180 g/mol). The total
amount of glucose normally in circulating human blood is
therefore about 3.3 to 7g (assuming an ordinary adult blood
volume of 5 litres, plausible for an average adult male).
Glucose levels rise after meals for an hour or two by a few
grams and are usually lowest in the morning, before the
first meal of the day. Transported via the bloodstream from
the intestines or liver to body cells, glucose is the primary
source of energy for body's cells, fats and oils (ie, lipids) The fluctuation of blood sugar (red) and the sugar-lowering hormone
being primarily a compact energy store. insulin (blue) in humans during the course of a day with three meals.
One of the effects of a sugar-rich vs a starch-rich meal is highlighted.
Failure to maintain blood glucose in the normal range leads
to conditions of persistently high (hyperglycemia) or low (hypoglycemia) blood sugar. Diabetes mellitus, characterized by
persistent hyperglycemia from any of several causes, is the most prominent disease related to failure of blood sugar regulation.
Contents
1 Normal values
2 Regulation
3 Glucose measurement
3.1 Sample type
3.2 Measurement techniques
3.3 Blood glucose laboratory tests
3.4 Clinical correlation
4 Health effects
5 Low blood sugar
6 Converting glucose units
7 Comparative content
8 Etymology and use of term
9 Blood glucose in birds and reptiles
10 References
11 See also
Normal values
Despite widely variable intervals between meals or the occasional consumption of meals with a substantial carbohydrate load,
human blood glucose levels normally remain within a remarkably narrow range. In most humans this varies from about
82 mg/dl to perhaps 110 mg/dl (4.4 to 6.1 mmol/l) except shortly after eating when the blood glucose level rises temporarily up
to maybe 140 mg/dl (7.8 mmol/l) or a bit more in non-diabetics. The American Diabetes Association recommends a post-meal
glucose level less than 180 mg/dl (10 mmol/l) and a pre-meal plasma glucose of 90-130 mg/dl (5 to 7.2 mmol/l). [1]
It is usually a surprise to realize how little glucose is actually maintained in the blood and body fluids. The control mechanism
works on very small quantities. In a healthy adult male of 75 kg (165 lb) with a blood volume of 5 litres (1.3 gal), a blood](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-9-320.jpg)
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Normal values Reference ranges for blood tests
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Glucose measurement
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Reference
Measurement techniques Blood sugar
Blood glucose laboratory tests
Clinical correlation For the song by Pendulum, see Blood Sugar / Axle Grinder.
Health effects
Blood sugar concentration, or glucose level, refers to
Low blood sugar the amount of glucose present in the blood of a human or
Converting glucose units animal. Normally, in mammals the blood glucose level is
Comparative content maintained at a reference range between about 3.6 and
Etymology and use of term 5.8 mM (mmol/l). It is tightly regulated as a part of
Blood glucose in birds and metabolic homeostasis.
reptiles
Mean normal blood glucose levels in humans are about 90
References
mg/dl, equivalent to 5mM (mmol/l) (since the molecular
See also weight of glucose, C6H12O6, is about 180 g/mol). The total
amount of glucose normally in circulating human blood is
1 therefore about 3.3 to 7g (assuming an ordinary adult
... Locations
v... blood volume of 5 litres, plausible for an average adult
male). Glucose levels rise after meals for an hour or two
by a few grams and are usually lowest in the morning,
before the first meal of the day. Transported via the
bloodstream from the intestines or liver to body cells,
glucose is the primary source of energy for body's cells, The fluctuation of blood sugar (red) and the sugar-lowering hormone
fats and oils (ie, lipids) being primarily a compact energy insulin (blue) in humans during the course of a day with three meals.
One of the effects of a sugar-rich vs a starch-rich meal is highlighted.
store.
Failure to maintain blood glucose in the normal range leads to conditions of persistently high (hyperglycemia) or low (hypoglycemia)
Images Videos
blood sugar. Diabetes mellitus, characterized by persistent hyperglycemia from any of several causes, is the most prominent disease
related to failure of blood sugar regulation.
Normal values view all 24 view all 15
Despite widely variable intervals between meals or the occasional consumption of meals with a substantial carbohydrate load,
human blood glucose levels normally remain within a remarkably narrow range. In most humans this varies from about 80 mg/dl to
perhaps 110 mg/dl (4.4 to 6.1 mmol/l) except shortly after eating when the blood glucose level rises temporarily up to maybe 140
mg/dl (7.8 mmol/l) or a bit more in non-diabetics. The American Diabetes Association recommends a post-meal glucose level less
than 180 mg/dl (10 mmol/l) and a pre-meal plasma glucose of 90-130 mg/dl (5 to 7.2 mmol/l). [1]
It is usually a surprise to realize how little glucose is actually maintained in the blood and body fluids. The control mechanism works
on very small quantities. In a healthy adult male of 75 kg (165 lb) with a blood volume of 5 litres (1.3 gal), a blood glucose level of
100 mg/dl or 5.5 mmol/l corresponds to about 5 g (0.2 oz or 0.002 gal, 1/500 of the total) of glucose in the blood and approximately
45 g (1½ ounces) in the total body water (which obviously includes more than merely blood and will be usually about 60% of the total
body weight in men). A more familiar comparison may help – 5 grams of glucose is about equivalent to a small sugar packet as
provided in many restaurants with coffee or tea, with people using typically 1 to 3 packets per cup.
Regulation
Main article: Blood sugar regulation
The homeostatic mechanism which keeps the blood value of glucose in a remarkably narrow range is composed of several
interacting systems, of which hormone regulation is the most important.
There are two types of mutually antagonistic metabolic hormones affecting blood glucose levels:
catabolic hormones (such as glucagon, growth hormone, cortisol and catecholamines) which increase blood glucose;
and one anabolic hormone (insulin), which decreases blood glucose.
Glucose measurement
Main article: Blood glucose monitoring
Sample type
Glucose can be measured in whole blood, serum (ie, plasma). Historically, blood glucose values were given in terms of whole blood,
but most laboratories now measure and report the serum glucose levels. Because red blood cells (erythrocytes) have a higher
concentration of protein (eg, hemoglobin) than serum, serum has a higher water content and consequently more dissolved glucose
than does whole blood. To convert from whole-blood glucose, multiplication by 1.15 has been shown to generally give the
serum/plasma level.
Collection of blood in clot tubes for serum chemistry analysis permits the metabolism of glucose in the sample by blood cells until
separated by centrifugation. Red blood cells, for instance, do not require insulin to intake glucose from the blood. Higher than normal
amounts of white or red blood cell counts can lead to excessive glycolysis in the sample with substantial reduction of glucose level if
the sample is not processed quickly. Ambient temperature at which the blood sample is kept prior to centrifuging and separation of
plasma/serum also affects glucose levels. At refrigerator temperatures, glucose remains relatively stable for several hours in a blood
sample. At room temperature (25 °C), a loss of 1 to 2% of total glucose per hour should be expected in whole blood samples. Loss of
glucose under these conditions can be prevented by using Fluoride tubes (ie, gray-top) since fluoride inhibits glycolysis. However,
these should only be used when blood will be transported from one hospital laboratory to another for glucose measurement. Red-top
serum separator tubes also preserve glucose in samples after being centrifuged isolating the serum from cells.
Particular care should be given to drawing blood samples from the arm opposite the one in which an intravenous line is inserted, to
prevent contamination of the sample with intravenous fluids. Alternatively, blood can be drawn from the same arm with an IV line
after the IV has been turned off for at least 5 minutes, and the arm elevated to drain infused fluids away from the vein. Inattention can
lead to large errors, since as little as 10% contamination with 5% dextrose (D5W) will elevate glucose in a sample by 500 mg/dl or
more. Remember that the actual concentration of glucose in blood is very low, even in the hyperglycemic.
Arterial, capillary and venous blood have comparable glucose levels in a fasting individual. After meals venous levels are somewhat
lower than capillary or arterial blood; a common estimate is about 10%.
Measurement techniques
Two major methods have been used to measure glucose. The first, still in use in some places, is a chemical method exploiting the](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-16-320.jpg)
![Section VI . The Kidneys And The Body Fluids
This section was written following fruitful discussions with my colleagues Peter Bie, Niels-Henrik Holstein-
Rathlou, Paul Leyssac, Finn Michael Karlsen, and medical students Margrethe Lynggaard and Mads Dalsgaard.
The concept flux is net-transport of substance per time unit across an area unit. Flux is equal to concentration
multiplied by flow or mol per time unit across a barrier area Frequently used abbreviations in this section are
Chapter 24 Chapter 24.
Body Fluids and
Regulation Body Fluids And Regulation
Study Objectives
Principles
Definitions
Study Objectives
Essentials • To define the concepts: Dehydration, hyponatraemia, intracellular fluid volume (ICV),
Pathophysiology
Equations
extracellular fluid volume (ECV), interstitial fluid (ISF), overhydration, oxidation water,
Self-Assessment radioactivity, specific activity, and total body water.
Answers
Highlights • To describe the daily water balance, the K+ - and Na+ -balance, sweat secretion, the
Further Reading ionic composition in blood plasma, the water content of fat- and muscle- tissue and the
Fig. 24-1
daily water transfer across the gastro-intestinal mucosa. To describe the osmotic pressure
Fig. 24-2
Fig. 24-3
in the body fluids, the measurement of fluid compartments by indicator dilution, the
Fig. 24-4 measurement of total body-K+ and -Na+ and the related dynamic pools.
Fig. 24-5
Fig. 24-6 • To draw models of the body fluid compartments.
Fig. 24-7
Fig. 24-8
• To explain the influence of age, sex and weight on the size of the total body water and
Fig. 24-9
Fig. 24-10 its phases. To explain disorders with increased or reduced extracellular fluid volume and
shock.
Return to chapter 24
Return to Content • To apply and use the above concepts in problem solving and in case histories.
Principles
• The law of conservation of matter states that mass or energy can neither be created
nor destroyed (the principle of mass balance). The principle is here used to measure
physiological fluid compartments and the body content of ions.
Definitions
• Concentration: The concentration of a solute is the amount of solute in a given fluid
volume.
• Dehydration is a clinical condition with an abnormal reduction of one or more of the
major fluid compartments (ie, total body water with shrinkage of blood volume or ISF).
• Dextrans are polysaccharides of high molecular weight.
• Intracellular fluid volume (ICV) refers to the volume of fluid inside all cells. This
volume normally contains 26-28 litre (l) out of the total 42 l of water in a 70-kg person.
- One litre of water equals one kg of water.
• Extracellular fluid volume (ECV) refers to the interstitial and the plasma volume.
The ECV contains the remaining water (14-16 kg) with most of the water in tissue fluid
(ISF) and about 3 kg of water in plasma. - Interstitial fluid (ISF) is the tissue fluid
between the cells in the extravascular space.
• Hyperkalaemia refers to a clinical condition with plasma-[K+ ] above 5 mM (mmol/l
of plasma).
+](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-24-320.jpg)
![• Hypokalaemia refers to a clinical condition with plasma-[K ] below 3.5 mM.
• Hypernatraemia refers to a clinical condition with plasma-[Na+ ] above 145 mM.
• Hyponatraemia refers to a clinical condition with plasma-[Na+ ] below 135 mM.
• Oedema refers to a clinical condition with an abnormal accumulation of tissue fluid or
interstitial fluid.
• Osmolality is a measure of the osmotic active particles in one kg of water. Plasma-
osmolality is given in Osmol per kg of water. Water occupies 93-94% of plasma in
healthy persons. Plasma osmolality is normally maintained constant by the antidiuretic
hormone feedback system.
• Overhydration refers to a clinical condition with an abnormal increase in total body
water resulting in an increased ECV and thus salt accumulation.
• Oxidation water or metabolic water (oxidative phosphorylation) refers to the daily
water production by combustion of food - normally 300-400 g of water daily in an adult.
• Radioactivity is measured as the number of radioactive disintegrations per s (in
Becquerel or Bq per l). One disintegration per s equals one Bq.
• Total body water is destributed between two compartments separated by the cell
membrane: The intracellular and the extracellular fluid.
Essentials
This paragraph deals with 1. The three major fluid compartments, 2. Water balance, 3.
Body potassium, 4. Body sodium, 5. The indicator dilution principle, 6. The renin-
angiotensin-aldosterone cascade, 7. Output contol, 8. Regulation of renal water excretion,
and 9. Regulation of renal sodium excretion.
Read first about the nephron (paragraph 1 of Chapter 25).
1. The three major fluid compartments
The three major body fluid compartments are the intracellular fluid volume (ICV), the
interstitial fluid volume (ISV) and the vascular space (Chapter 1, Fig.1-4). Water
permeable membranes separate the three compartments, so that they contain almost the
same number of osmotically active particles per kg. The three compartments have the same
concentration expressed as mOsmol per kg of water or the same freeze-point depression.
They are said to be isosmolal, because they have the same osmolality.
The so-called lean body mass, which means a body stripped of fat, contains 0.69 parts of
water (69%) of the total body weight in all persons. - Such high values are observed in the
newborn and in extremely fit athletes with minimal body fat. Babies have a tenfold higher
water turnover per kg of body weight than adults do.
As an average females have a low body water percentage compared to males. Such
differences show sex dependency, but the important factor is the relative content of body
fat, since fat tissue contains significantly less water (only 10%) than muscle and other
tissues (70%). This is why the relative water content depends upon the relative fat content.
The average for most healthy persons is 60% of the body weight. Sedentary, overweight
persons contain only 50-55 % water dependent on the body fat content.
The relative content of body fat rises with increasing age and body weight, and the relative
mass of muscle tissue becomes less. Consequently, the body water fraction falls with
increasing body weight and age. Aging implies loss of cells, but the ECV is remarkably](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-25-320.jpg)
![constant through life and under disease conditions.
Each body (weight 70 kg) contains 4 mol of both sodium and potassium (ie, the total ion
pool). A minor fraction of the potassium is radioactive. The calcium and magnesium
content is 25 and 1 mol, respectively.
In the renal tubule cells the epithelium is a single layer of cells, joined by junctional
complexes near their luminal border (Fig. 25-7). Solutes can traverse the epithelium
through transcellular or paracellular pathways. Virtually every cell membrane in the body
contains the Na+ - K+ -pump, which maintains the low intracellular Na+ -concentration and
develops the negative, intracellular voltage. In the renal tubule cells the Na+ - K+ -pump, is
located in the basolateral membrane. Read more about the nephron in Chapter 25 and about
hormonal control later in paragraph 8 and 11 of this Chapter.
Unfortunately, the simple laws of dilute solutions are unprecise at physiological
concentrations. Rough estimates are based on the assumptions that extracellular sodium is
associated with monovalent anions and that deviations in osmolality are twice the deviation
in plasma sodium concentration.
ICV: The dominating intracellular solute is potassium (K+ ), balanced by phosphate and
anionic protein, whilst the dominating extracellular solute is NaCl. All compartments have
almost the same osmolality 300 mOsmol* kg-1 of water. The thin cell membrane - or the
endothelial barrier between ISF and plasma in the vascular phase - cannot carry any
important hydrostatic gradient. Water passes freely between the extra- and intra-cellular
compartment, as osmotic forces govern its distribution and the membranes are water
permeable.
Fig. 24-1: The daily water transfer across the gastrointestinal barrier in a healthy
standard person.
The ICV comprises 26-28 kg out of the total 42-kg of water in a 70-kg person (Fig. 1-4).
ECV: The ECV compartment comprises the remaining water (14-16 kg) with most of the
water in tissue fluid (interstitial fluid or ISF) and 3 kg of water in plasma (Chapter 1, Fig.
1-4). The size of the ECV compartment is proportional to the total body Na+ . Changes in
plasma osmolality indicate problems in water balance.
A [Na+ ] in ECV of 150 mmol per kg of plasma water corresponds to a total osmolality of
300 mOsmol per kg.
Alterations in plasma-[Na+ ] (osmolality) will be followed by similar changes of the ECV
osmolality, because the permeability of of the capillary barrier for Na+ and water is almost
equal.
The daily water transfer across the gastrointestinal tract amounts to approximately 9 l in
each direction (Fig. 24-1).
2. Water balance
A healthy person on a mixed diet in a temperate climate receives 1000 ml with the food
and drinks 1200 ml daily. Balance is maintained as long as the water loss is the same (Fig.
24-2).
Fig. 24-2: The daily water balance in a 70-kg healthy person on a mixed diet. The
apparent imbalance between input (2200 ml) and output (2500 ml) is covered by 300
ml of metabolic water.
Water is lost in the urine (1500 ml), in the stools (100 ml), in sweat and evaporation from
the respiratory tract (900 ml) as a typical example.
The total loss of water is 2500 ml, and this corresponds perfectly to the intake plus a
normal production of 300 ml of metabolic water per 24 hours (Fig. 24-2).](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-26-320.jpg)
![3. Body potassium
The daily dietary intake of potassium varies with the amount of fruit and vegetables
consumed (75-150 mmol K+ daily).
More than 90% of the body potassium is located intracellularly. Only a few percent of the
K+ in the body pool are found outside the cells and subject to control (Fig. 24-3). The
main renal K+ -reabsorption is passive and paracellular through tight junctions of the
proximal tubules. Moreover K+ -excretion can vary over a wide range from almost
complete reabsorption of filtered K+ to urinary excretion rates in excess of filtered load (ie,
net secretion of K+ ).
The Na+ -K+ -pump located in the cell membrane, maintains the high intracellular [K+ ] and
the low intracellular [Na+ ]. The energy of the terminal phosphate bond of ATP is used to
actively extrude Na+ and pump K+ into the cell. The membrane also contains many K+ -
and Cl - -channels, through which the two ions leak out of the cell.
In myocardial cells, as in skeletal muscle and nerve cells, K+ plays a major role in
determining the resting membrane potential (RMP), and K+ is important for optimal
operation of enzymatic processes.
Under normal conditions, the RMP of the myocardial cell is determined by the dynamic
balance between the membrane conductance to K+ and to Na+ . As [K+ ] out is reduced
during hypokalaemia, the membrane depolarises causing voltage-dependent inactivation of
K+ -channels and activation of Na+ -channels, allowing Na+ to make a proportionally larger
contribution to the RMP.
Fig. 24-3: The total body K + -pool in a healthy person comprises 4000 mmol with
more than 90% intracellularly. The normal ECG and the ECG of a patient with
hyperkalaemia is shown to the right.
The K+ -permeability is around 50 times larger than the Na+ -permeability, so the RMP of
normal myocardial cells (typically: -90 mV) almost equals the equilibrium potential for K +
(-94 mV).
The excretion of K+ by overload is almost entirely determined by the extent of distal tubular
secretion in the principal cells. Any rise in serum [K+ ] immediately results in a marked
rise in K+ -secretion. This transport mechanism is controlled by aldosterone and by K+ .
Aldosterone stimulates the secretion of K+ and H+ by the principal cells of the renal distal
tubules and collecting ducts (Fig. 25-11). This is why chronic acidosis decreases and
chronic alkalosis increases K+ -secretion. – Actually, acute acidosis may reduce K+ -
secretion.
Of the consumed K+ , 75-150 mmol is daily absorbed in the intestine. Since 90% is
excreted renally in a healthy person, there must be a minimum in a typical volume of 1500
ml of daily urine with a concentration of (75/1.5) = 50 mM. Normal urinary [K+ ] is at least
30 mM. A high urinary [K+ ] is indicative of a high total body K+ or a high intake of K+ .
The normal excretion fraction (Chapter 25) for K+ is 0.10 (10% or 90 mmol of the 900
mmol in the daily filtrate) corresponding to the daily intake (Fig. 24-4). A K+ -poor diet
leads to hypokalaemia with less than 20 mmol K+ in the daily urine. A K+ -rich diet
triggers a large secretion and a high excretion in the urine (Box 25-1). A low urinary [K+ ]](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-27-320.jpg)
![is indicative of a low total body K+ or of extracellular acidosis with transfer of K + from
the cells in exchange of H+ . A low [K+ ] in the distal tubule cells reduces the K+ -excretion.
The normal plasma-[K+] level is dependent upon the exchange with the cells, the renal
excretion rate, and the extrarenal losses through the gastrointestinal tract or through sweat.
Measurement of total and exchangeable body potassium
Our natural body potassium is 39K, but we also contain traces of naturally occurring
radioactivity (0.00012 or 0.012% is 40K with a half-life of 1.3×109 years). When using this
natural tracer, injection of radioactive tracer is avoided.
The person to be examined is placed in a sensitive whole body counter, and the total
activity of the tracer 40K in the body (S Bq) is measured.
Specific activity (SA) is the concentration of radioactive tracer in a fluid volume divided
by the concentration of naturally occurring, non-radioactive mother-substance. The
concentration of mother-substance is traditionally measured in mmol per l (mM). SA is
equal to radioactivity (A) per non-radioactive mass unit, m (ie, A/m in Bq/mol). Following
even distribution, the SA for a certain substance must be the same all over the body. SA is
preferably measured in plasma (with scintillation counters or similar equipment).
Specific activity (SA) is here the number of Bq 40K per mol of mother substance ( 39K) in
the whole body. We can calculate all 39K or total body potassium: S/SA mol per whole
body - when SA is known to be 0.012% or a fraction of 0.00012. The total body potassium
of a healthy person is 4000 mmol. The SA of 40K implies a 40K/39K ratio of 0.48
mmol/4000 mmol (=0.00012).
An exchangeable ion pool in our body is the dynamic part of the total specific ion content.
The remaining content is fixed as insoluble salts in the bones. The dynamic character
implies the use of a dilution principle to measure such a pool.
In order to measure the exchangeable body potassium pool, a radioactive tracer is injected,
such as 42K with a physical half-life of 12 hours (12.4 hours) and urine is collected. The
first urine sample is from the first 12 hours, and the second sample is covering 12 - 24
hours. The total tracer dose given must be adjusted for by the loss of tracer in the urine
and by the radioactive decay during the first 12 hours mixing period. The two urine
samples obtained are examined for tracer and for natural potassium. The tracer is assumed
to distribute just as natural potassium after 12 - 24 hours. When the tracer is distributed
evenly in the exchangeable body potassium, its SA must be the same in urine, plasma or
elsewhere in the body. The exchangeable body potassium is calculated by Eq. 24-2 .
The specific activity for the tracer (SA Bq per mol) is known from the plasma
measurements. In this way we measure the exchangeable body potassium. The normal
values are 41 mmol 39K per kg body weight for females, and 46 mmol per kg for males.
4. Body sodium ( 23Na)
The exchangeable body sodium is easy to measure using the dilution principle and a
minimum of equipment.
Our natural non-radioactive body sodium is 23Na. We administer the radioactive tracer,
24Na, with a physical half-life of 15 hours. We have to use a total period of 30 hours to
secure even distribution in the ECV.
The total tracer dose given, must be adjusted for by the loss of tracer in the urine, and the
radioactive decay of 24Na (see the decay law in Chapter 1). The exchangeable body
sodium is calculated by Eq. 24-2.
We know the specific activity for the tracer (SA Bq/mol) from the plasma measurements;
23](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-28-320.jpg)
![depends upon several effector mechanisms out of which three are classical:
The first factor is the glomerular filtration rate (GFR), which is responsible for the size of
the filtered flux of Na+ across the glomerular barrier in the kidneys. Renal prostaglandins,
generated in response to angiotensin II, are involved in maintaining the filtered flux of Na+ .
The second factor is the renin-angiotensin-aldosterone cascade (Fig. 24-5).
The third factor consists of peptides with natriuretic effects. The most well-known peptide
is called atrial natriuretic peptide (ANP) and originates from granules of the atrial
myocytes. A low circulating blood volume with low atrial pressure increases renal
sympathetic tone, reduces the stimulus of the low-pressure receptors in the atrial wall and
thus the ANP secretion. Hereby, the natriuresis is reduced. - Renal natriuretic peptide or
urodilatin from the distal tubule cells is related to ANP. Urodilatin has been isolated from
human urine and contains four amino acids more than ANP.
An increase in effective circulating blood volume, increases atrial pressure, reduces
sympathetic tone and releases ANP and urodilatin leading to increased natriuresis.
The main purpose of these mechanisms is to maintain an effective circulating blood volume
by an increase or a decrease of the renal excretion of Na+ . Initially, osmolality control is
dominating. Finally, after a dangerous reduction in blood volume, volume-pressure
receptors override the hypothalamic osmoreceptors and stimulate the ADH release and
thirst. In the terminal phase, the body protects effective circulating blood volume at the
expense of ECF osmolality.
Pathophysiology
This paragraph deals with 1. Dehydration, 2. Overhydration, 3. Hyponatraemia, 4.
Hypernatraemia, 5. Hypokalaemia, and 6. Hyperkalaemia.
1. Dehydration
Dehydration is an abnormal reduction of the major fluid volumes (total body water with
shrinkage of ECV). When we lose more than 5% of the total body water it has clinical
consequences. The condition is life threatening if the patient loses 20 %.
Accidents and surgery with a period of water deprivation, imply a rise in ECF osmolality
and thus stimulation of both thirst and the hypothalamic osmoreceptors, whereby ADH is
released. - Symptoms and signs of dehydration are thirst, dry mucous membranes, and
decreased skin elasticity or turgor due to loss of ISF.
Loss of effective circulating blood volume implies a low blood pressure in both the venous
and the arterial system. Loss of more than one litre of ECV causes postural hypotension
with dizziness, confusion and cerebral failure. Empty veins and cold skin characterise the
peripheral venoconstriction. Finally, there is extreme tachycardia, which turns into terminal
bradycardia and an arterial blood pressure that approach zero.
Loss of salt and water frequently develops into hypo-osmolal dehydration (Fig. 24-8). This
is because the thirst forces the patient to drink (salt free) water. Water dragged into the
cells further reduces the hyposmolal ECV (Fig. 24-8). The small ECV elicits a
hyperaldosteronism, which is called secondary, because it is not initiated as primary
hypercorticism in the adrenal cortex. A precise compensation of the water loss results in
pure hyponatraemia, where water eventually is drawn from ECV into the cells. The low
[Na+ ] around the swelling cells reduces the potential gradient across the cell membranes
with increased neuromuscular irritability (muscular twitching) and cardiac arrhythmias.
Isosmolal dehydration is a proportional loss of water and solutes. There is no concentration](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-33-320.jpg)
![gradient over the cell membranes, and the loss is mainly from ECV (Fig. 24-8).
Fig. 24-8: Dehydration (hyperosmolal, isosmolal and hyposmolal).
Hyperosmolal dehydration occurs in persons deprived of water. The hyperosmolal ECV
drags water from ICV and dehydrates the cells (Fig. 24-8). This is intracellular
dehydration.
The hyperosmolality liberates ADH to restrict the water loss. The patient excretes a very
small urine volume.
Persons deprived of water at sea may drink seawater. Sea water is hypertonic saline and the
victims die faster. When hypertonic saline reaches the ECV it aggravates the intracellular
dehydration simultaneously with an extracellular overhydration. Intracellular dehydration
leads to respiratory arrest and death of thirst.
2. Overhydration
Overhydration is an abnormal increase of total body water - in particular ECV, and thus
salt accumulation. The increase in the interstitial fluid volume is called oedema.
Overhydration frequently occurs among patients in fluid therapy (ie, overhydration of
iatrogenous origin).
Increased salt intake by mouth is compensated by increased salt excretion by normal
kidneys.
However, a large saline infusion (0.9% NaCl) will expand ECV and total body water
(isosmolal overhydration in Fig. 24-9). Inappropriately large infusions of saline lead to
iatrogenous hyperosmolal overhydration, if they lose more water than salt (Fig. 24-9).
Hyperosmolality drags water from the cells, so that the patient develops intracellular
dehydration with hallucinations, loss of consciousness and eventually respiratory arrest.
The patient with hyposmolal overhydration is typically in fluid treatment and develops
muscle cramps and disorientation. The skin turgor is normal. A low serum - [Na+ ]
confirms the diagnosis. The water overload in ECV is dragged into the cells in hyposmolal
overhydration until osmolality balance (Fig. 24-9).
In the brain and the muscles this intracellular overhydration causes headache,
disorientation, increased spinal pressure, coma and muscle cramps. Both hyposmolal and
hyperosmolal intracellular overhydration conditions are characterised by cerebral
symptoms and signs.
Fig. 24-9: Overhydration (hyperosmolal, isosmolal, and hyposmolal).
Acute renal failure with decreased GFR reduces the flux of filtered NaCl (first factor) and
thus the Na+ -excretion.
Oedema is a clinical condition where the interstitial fluid volume (ISF) is abnormally large.
A voluminous ISF is usually due to increased hydrostatic venous pressure (heart
insufficiency), or a reduced colloid osmotic pressure (hypoproteinaemia) as predicted from
Starlings law for transcapillary transport.
Reduced protein synthesis (liver disease) and abnormal protein loss with the urine
(proteinuria) causes hypoproteinaemia. Thus protein-losing kidneys are involved.
Capillary damage (allergy, burns, inflammation etc) with increased capillary permeability
causes local oedema. – Obstruction to lymphatic drainage can also cause oedema (scarring
after radiation therapy, elephantiasis etc).
Cardiac insufficiency with increased venous pressure and oedema formation increases](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-34-320.jpg)
![sympathetic tone and thus releases the renin-angiotensin-aldosterone cascade (Fig. 24-5)
causing Na+ -retention.
Hepatic cirrhosis activates the cascade in a similar way - possibly including the release of
nitric oxide.
Hypoalbuminaemia reduces the colloid osmotic pressure of plasma, whereby water is
distributed from the vascular space to the ISF. The fall in effective circulatory volume
activates the renin cascade and leads to Na+ -retention.
NSAIDs can activate the renin-angiotensin-aldosterone cascade, and the increased
aldosterone leads to Na+ -retention and overhydration.
Angiotensin II-receptor antagonists and ACE-inhibitors are utilized clinically to block the
effects of angiotensin II in congestive heart failure, diabetes mellitus and hypertension.
Blockade of the cascade reduces both preglomerular and postglomerular resistances.
The supine position at bed rest increases venous return. This implies an increased cardiac
output (Starlings law), a reduced ANF secretion from the atrial walls and a reduced renin-
angiotensin-aldosterone cascade. This is why bed rest is beneficial for disorders with salt
accumulation.
3. Hyponatraemia
Hyponatraemia (ie, plasma-[Na+ ] below 135 mM) is associated with dehydration,
overhydration or normohydration (ie, a normal ECV and total body sodium content).
Hyponatraemia with reduced ECV (ie, salt-deficient hyponatraemia) is caused by a salt
loss in excess of the high water loss (ie, hyposmolal dehydration in Fig 24-10). This is seen
in any type of hypoadrenalism including the rare primary hypoadrenalism (Addison’s
disease).
In Addison’s disease the entire adrenal cortex is destroyed by autoimmune reactions (80%)
or by malignancy or infection. All three types of hormones are insufficiently produced
(mineralocorticoids, glucocorticoids and sex hormones). The lack of aldosterone leads to
Na+ -excretion and K+ -retention with hyponatraemia combined with hyperkalaemia
resulting in dehydration and hypotension.
Hyponatraemia is developed in the following way (Fig. 24-10):
1. The first step is the salt loss in excess of the water loss.
2. Since the ECF-[Na+ ] is low, the ADH secretion is suppressed, and the water excretion
is increased. Hereby, both the ISF and the vascular spaces are reduced often by more than
10%.
3. This is an adequate stimulus for the volume-pressure receptors, which override the
osmoreceptors, whenever the effective circulatory volume is threatened.
Fig. 24-10: The three body fluid compartments in a patient with salt-deficient
hyponatraemia.
The volume-pressure receptors stimulate both thirst and the release of ADH. The effective
circulating volume is protected at the expense of osmolality! Still the blood pressure is
falling, which impairs cerebral perfusion, causing confusion, headache and coma.
The hyponatraemia implies a reduced resting membrane potential and thus a low threshold
for neuromuscular stimulation resulting in muscle cramps.
The large renal loss is seen with osmotic diuresis (hyperglycaemia and uraemia), excessive](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-35-320.jpg)
![use of diuretics, renal tubular reabsorption defects, adreno-cortical insufficiency as
aldosterone-antagonist-intoxication or other types of hypoaldosteronism.
The extra-renal loss is often large from excessive sweating, diarrhoea, haemorrhage,
vomiting, loss with ascites or bronchial secretion, and transudation from cutaneous defects.
Normal kidneys normally compensate extra-renal loss. The urinary excretion of salt and
water falls in response to volume depletion, so the urine is concentrated - but with less than
10 mM Na+ .
Normal sweat is a hypotonic solution, because Na+ is reabsorbed in the duct system. The
[Na+ ] can increase up to 80 mM with increasing sweat flow - due to the limited time for
the aldosterone-controlled Na+ -reabsorption.
Increased salt intake by mouth or intravenously is required as a supplement to the
treatment directed at the primary cause.
Low plasma- [Na+ ] in a chronically salt-deficient patient suggests a high aldosterone
secretion from the adrenal zona glomerulosa. Further administration of aldosterone
therefore may not have any effect.
Hyponatraemia with increased ECV (water-excess hyponatraemia) is often caused by
cardiac, hepatic, and renal insufficiency or by hypoalbuminaemia - see hyposmolal
overhydration (Fig. 24-9).
Hyponatraemia with normal ECV is often caused by stress (surgery, psychogenic
polydipsia), abnormally high ADH release (in the syndrome of inappropriate antidiuretic
hormone secretion, and in vagal neuropathy), increased sensitivity to ADH by drugs such
as chlorpropamide and tolbutamide, or by intake of ADH-like substances (oxytocin).
Pseudo-hyponatraemia is characterised by a spuriously low plasma value measured
conventionally in the total volume of plasma, which includes an extra volume in cases with
hyperlipidaemia or hyperproteinaemia etc. Plasma osmolality or plasma-Na+ measured
with ion selective electrodes is the choise and the direct read value is normal. This is
because Na+ is confined to the aqueous phase.
Treatment of artefactual hyponatraemia (taking blood from an extremity into which
isotonic glucose is infused) is also unnecessary.
4. Hypernatraemia
The normal plasma-[Na+ ] is 135-145 mM, and values above 170 mM are rare. Excessive
infusion of saline (0.9% NaCl or 154 mM) can lead to hypernatraemia. Such alarmingly
high levels create an emergency situation, where glucose infusion is indicated initially in
order to reduce the high level slowly. The increased plasma osmolality elicits a strong
desire to drink.
The cause is sometimes water deficit due to pituitary diabetes insipidus, or to nephrogenic
diabetes insipidus, where ingestion of nephrotoxic drugs have made the renal collecting
ducts resistant to ADH. – Osmotic diuresis also causes water deficit with hypernatraemia
just as excessive loss of water through the skin or lungs.
Primary hyperaldosteronism (Conns disease) and all types of secondary
hyperaldosteronism also lead to hypernatraemia combined with hypokalaemia and enlarged
blood volume.
Cerebral failure and convulsions are alarming signs, but there are no specific symptoms and
signs of hypernatraemia.](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-36-320.jpg)
![Polyuria, polydipsia and thirst suggest diabetes. Diabetes mellitus is easy to diagnose, and
diabetes insipidus shows a low urinary osmolality. Pituitary diabetes insipidus is treated
with an analogue of ADH (desmopressin, with a low pressor-effect).
5. Hypokalaemia
The normal potassium ion concentration in blood plasma is 3.5-5 mM. Hypokalaemia is
caused by renal or extra-renal K+ -loss or by restricted intake.
Long standing use of diuretics without KCl compensation is a frequent cause of
hypokalaemia.
Hyperaldosteronism (increased aldosterone secretion) is another cause.
Vomit fluid only contains 5-10 mM of K+ . Still, prolonged vomiting develops into
hypokalaemia, because the Na+ -loss stimulates the aldosterone secretion, which increases
K + -excretion in the kidneys.
Profuse diarrhoea causes marked hypokalaemia, also because the diarrhoea fluid contains
up to 50 mM of K + .
Hypokalaemia is seen in cardiac patients receiving digoxin treatment. Digoxin toxicity is
imminent, because digoxin firmly binds to myocardial cells in hypokalaemia. Treatment
must be directed towards the underlying cause. Infusion of potassium -rich fluid is
dangerous, because of the marginal distance to hyperkalaemia.
The reduced extracellular K+ hyperpolarises the cell membrane (increases the negativity of
the voltage across the membrane). This reduces the excitability of neurons and muscle
cells. Thus, hypokalaemia can result in muscle weakness and paresis. Hypokalaemia is
associated with an increased frequency of cardiac arrhythmias with atrial and ventricular
ectopic beats in particular in patients with cardiac disease . - Hypokalaemia inhibits release
of adrenaline, aldosterone and insulin.
6. Hyperkalaemia
Acute hyperkalaemia (ie, plasma-[K+ ] above 5 mM) is a normal condition following
severe exercise, and normal kidneys easily eliminate K+ .
In disease states the causes are insufficient renal excretion or increased release from
damaged body cells as during long lasting hunger, exercise or in severe burns. A plasma-
[K+ ] above 7 mM is life threatening due to asystolic cardiac arrest.
Long term intake of b-blocking drugs, which inhibit the Na+ -K+ -pump, leads to
hyperkalaemia that is accentuated by exercise.
Hyperkalaemia reduces the size of the resting membrane potential (reduces the negativity
of the voltage), whereby the threshold for firing is approached in neurons and striated
muscle cells. The increased excitability in hyperkalaemia results in muscle contractions,
cramps followed by muscle weakness. Hyperkalaemia leads to decreased cardiac
excitability, hypotension, bradycardia and eventual asystole. The ECG is characterised by
increased duration of the QRS-complexes and tented T-waves due to abrupt Ca2+-influx,
contraction, and abrupt Ca2+ -binding (Fig. 24-3). Cardiac arrest occurs as ventricular
fibrillation (the heart can never produce smooth tetanus) or as asystole.
Insulin is used to drive K+ back into the cells - either by insulin infusion or by glucose
infusion in order to release more insulin from the pancreatic islets. Usually, a combined](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-37-320.jpg)
![glucose-insulin drop is applied.
Other hormones (adrenaline, aldosterone) also stimulate the Na+ -K+ -pump and thereby
increase cellular K+ -influx (Fig. 24-3)
Equations
• The indicator dilution method: The indicator n mmol distributes in V litres of distribu-
tion volume. We measure the concentration Cp in mM, following even distribution, and
calculate the volume, V:
Eq. 24-1: V = n/C p . (litre = mmol/(mmol/l)
• When the tracer is radioactive potassium and thus distributed evenly in the
exchangeable potassium pool, its specific Activity (SA) must be the same in urine,
plasma or elsewhere in the pool.
Eq. 24-2: Exchangeable body potassium =
(Injected - eliminated)/SA. (Mol = Bq/(Bq per mol)
We know the specific activity for the tracer (SA Bq per mol) from the plasma
measurements. In this way we measure the exchangeable body potassium. The normal
values are 41 mmol 39K per kg body weight for females, and 46 mmol per kg for males.
• The following concentrations are found in normal plasma:
[Na+ ] 135-145, [K+ ] 3.5-5, [Cl - ] 96-106, [bicarbonate] 24, and total-[Ca 2+] 2.5 mM.
• The concentration of low molecular ions in the ultrafiltrate is affected by the Donnan
effect (normally 5% for monovalent ions), and by the fractional content of water in
plasma (0.94 normally):
Eq. 24-3: [Low molecular ions] = Plasma conc. * Donnan factor/ 0.94.
[Na+ ] = 141× 0.95/0.94 = 143 mmol/l of ultrafiltrate. Based on the Donnan effect alone,
this result is less than 141. The Donnan effect on monovalent cations is simply more than
compensated by the protein volume effect or fractional content of water in plasma (0.94).
[Cl - ] = 103×1.05/0.94 = 115 mmol/l of ultrafiltrate. Based on the Donnan effect this result
should be greater than 103 and the protein volume effect contribute further. Such an
ultrafiltrate is present in the kidneys and in ISF.
• The extracellular fluid volume (ECV) can be measured if all inulin molecules are
collected in the urine over 10-15 hours after the inulin infusion stopped.
Eq. 24-4: ECV = Amount of inulin excreted/(Cp /0.94).
The inulin distribution volume is more or less identical to the ECV.
• Concentration of molecules in the filtrate are calculated as follows:
Eq. 24-5: Cfiltr = Cp ×Ffree /0.94 (mmol per l of ultrafiltrate).
This value depends upon the fractional content of water in plasma (F water = 0.94 l of water
per l of plasma) and of the fraction of free, unbound molecules (F free ). For uncharged, free
molecules like inulin Ffree is 1, and for protein-bound molecules Ffree is lower than 1
Self-Assessment
Multiple Choice Questions:
Each of the following statements has True/False options:
A. Hyponatraemia with normal ECV is often caused by stress, abnormally high ADH](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-38-320.jpg)
![release, increased sensitivity to ADH by drugs, or by intake of ADH-like substances.
B. The total water content of a healthy person is 60%, and an extremely obese adult
contains relatively more water.
C. Hyponatraemia is defined as a plasma-[Na+ ] below 145 mM.
D. A plasma- [K+ ] above 4.5 mM is life-threatening.
E. An infusion of one l of 5% glucose is distributed evenly into all three compartments
just as pure water. An infusion of one l of saline remains mainly in the ECV, whereas
an infusion of one l of macrodex stays mainly in the vascular space.
Case History A
A healthy male with a body weight of 70 kg has a normal extracellular osmolality (300
mOsmol kg -1 ), and a normal ICV/ECV of 28/14 kg or l of water.
One day he is the victim of severe burns and he suffers a water loss of 2.5 l of water (the
salt loss is covered).
1. Calculate the new ECV osmolality following the water loss.
2. Does this hyperosmolality have consequences?
3. Following total restitution of the water compartments the patient undergoes surgery with
skin grafts. During the long procedure he receives sufficient water by glucose infusion,
but he looses 900 mOsmol NaCl. Calculate the new osmolality.
4. Is it dangerous for a healthy individual to lose 6 kg of water without solutes?
5. Is it dangerous for a healthy individual to lose 6 kg of water as an isosmolal fluid from
the ECV?
Case History B
A female patient (age 22 years; weight 71 kg) is in hospital suspect of potassium
imbalance. She has taken diuretics for 2 years. She is tired and sleepy; her legs are
paretic. The ECG shows prolongation of the Q-T interval, depression of the S-T segments
and flattening of the T-waves. Her blood pH is 7.57 and the serum K+ -concentration is 2.9
mM. One morning she receives an intravenous injection of a solution containing the
radioactive isotope of potassium (555,000 Becquerel, Bq, of 42K+ with a physical half-life
of 12 hours). Following the injection her urine is collected in two periods (0-12 and 12 -24
hours). The first urine collection contained 40 mmol K+ ( 39K+) and 4144 Bq 42K+. The
second urine specimen contained 40 mmol K+ and 2220 Bq 42K+. Both urine specimens
were analysed for radioactivity exactly 24 hours after the injection, where the specific
activity of her plasma was 55.5 Bq/mmol. The 42K+, retained after the first 12 hours,
distribute in her body just like all other exchangeable K+. The body contains traces
(0.012% of the total) of naturally occurring radioactivity ( 40K) with a half-life of 1.3 × 109
years.
1. Calculate the exchangeable K+ pool of her body after the 12-hour distribution
period. - Is the result normal?
2. Calculate the elimination rate constant (k) for exchangeable K + in her body, and the
biological half-life for this K+ in hours. Calculate the ratio between the physical](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-39-320.jpg)
![(many metabolic processes are sensitive to pH). The acid-base balance is accomplished
by co-operative action of the kidneys and the lungs.
• Hypokalaemia reduces the excitability of neurons, muscle cells and the myocardial
syncytium. Thus, hypokalaemia can result in muscle weakness, paresis, and cardiac
arrhythmias with ectopic beats and cardiac arrest in diastole.
• Hyperkalaemia increases the excitability of neurons, muscle cells and the myocardium.
• Acute hyperkalaemia is a normal condition following severe exercise, and normal
kidneys easily eliminate this. In disease states the causes of hyperkalaemia are
insufficient renal excretion or increased release from the body cells as during long
lasting hunger.
• A plasma- [K+] above 7 mM is life threatening due to ventricular fibrillation or
cardiac arrest in systole. Tented T-waves and increased QRS-complexes characterise
the ECG.
Further Reading
Astrup, P, P. Bie, and H.C. Engell. ‘Salt and water in culture and medicine.’ Munksgaard,
Copenhagen, 1993.
Knox, F. G. “Physiology of potassium balance.” Am.J. Physiol. 275 (Adv. Physiol. Educ.
20): S142-S147, 1998.
Return to chapter 24
Return to Content](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-41-320.jpg)
![The glomerular filtration rate, GFR, is the volume of glomerular filtrate produced per min.
In healthy adults the GFR is remarkably constant about 180 l each day or 125 ml per min
due to intrarenal control mechanisms. In many diseases the renal bloodflow, RBF, and
GFR will fall, whereby the ability to eliminate waste products and to regulate body fluid
volume and composition will decline. The degree of impaired renal function is shown by
the measured GFR.
GFR is routinely measured as the endogenous creatinine clearance.
The endogenous creatinine production is from the creatine metabolism in muscles and
proportional to the muscle mass. In a 70-kg person creatinine is produced at a constant rate
of 1.2 mg per min (1730 mg daily). This production is remarkably constant from day to
day, only slightly affected by a normal protein intake, and equal to the rate of creatinine
excretion. Both the serum creatinine and the renal creatinine excretion fluctuate throughout
the day. Therefore, it is necessary to collect the urine for 6-24 hours and measure the
creatinine excretion rate (ie, the urine flow rate multiplied by the creatinine concentration
in the urine). A single venous blood sample analysed for creatinine in plasma is all that is
needed to provide the endogenous creatinine clearance (Eq. 25-1).
Theoretically, two small errors disturb the picture, but both are overestimates.
At the normally low plasma concentrations of creatinine, a modest tubular secretion of
creatinine from the blood is detectable resulting in up to 15% overestimation of the
creatinine excretion flux. Most laboratories measure creatinine in serum instead of plasma,
which results in an overestimation of plasma creatinine.
Thus, calculation of a fraction with both an overestimated nominator and denominator
results in a value close to that of GFR in almost all situations, where the renal function is
near normal.
With progressive renal failure the plasma creatinine rises, and the creatinine secretion
increases the nominator in the clearance expression even more, so the measured clearance
will overestimate GFR. Still, the clearance provides a fair clinical estimate of the renal
filtration capacity (GFR).
In most cases a normal creatinine clearance (above 70 ml plasma per min at any age) is
comparable with the normal range for serum creatinine (around 0.09 mM in Fig. 25-4). The
serum creatinine concentration is inversely proportional to the creatinine clearance, and
also a good estimate of GFR. Renal failure is almost always irreversible, when the serum
creatinine is above 0.7 mM.
Fig. 25-4: Creatinine clearance versus serum creatinine. – A low serum creatinine
indicates normal kidney function, but not always (see false negative concentrations). –
An elevated serum creatinine indicates kidney failure, but not always (see false
positive concentrations).
Serum [creatinine] and serum [urea] depend upon both protein turnover and kidney
function. The serum [creatinine] and [urea] are large after intake of meals extremely rich in
(fried) meat, although the kidney function is normal (false positive concentrations in Fig.
25-4). In some materials up to 15% of measured serum creatinine concentrations are
normal, although the kidney function fails (false negative values in Fig. 25-4). Long-term
hospitalisation often leads to muscular atrophy, which reduces creatinine production and
excretion. The serum creatinine concentration is maintained normal because of a similar
fall in kidney function (GFR).
Half the osmolality of normal urine is due to urea, and the other half is mainly due to
NaCl. The osmolarity of urine varies tremendously (from 50 to 1400 mOsmol per l).
Physiological changes of the renal bloodflow often parallel changes of GFR. A reduced
GFR implies a smaller tubular Na+ -reabsorption and thus a smaller O2 demand. When
kidneys are perfused by anoxic blood the tubular reabsorption is blocked first, and then the](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-47-320.jpg)
![GFR is reduced. As tubular Na+ -reabsorption is the main oxidative energy demanding
activity, a high GFR is correlated to high oxygen consumption in the normal kidney.
The size of GFR is determined by the factors shown in Fig. 25-7. The resistance of the
glomerular barrier is extremely small in healthy human kidneys.
2b. Inulin
Inulin is the ideal indicator for determination of GFR, because of the following three
relations:
1. Inulin is a polyfructose (from Jewish artichokes) without effect on GFR. Inulin has
a spherical configuration and a molecular weight of 5000. Inulin filters freely
through the glomerular barrier. Inulin is uncharged and not bound to proteins in
plasma. Inulin crosses freely most capillaries and yet does not traverse the cell
membrane (distribution volume is ECV). Since one litre of plasma contains around
0.94 l of water, the ultrafiltrate concentration of inulin is Cp /0.94.
2 All ultrafiltered inulin molecules pass to the urine. In other words, they are neither
reabsorbed nor secreted in the tubules. Inulin is an exogenous substance - not
synthesised or broken down in the body.
3. Inulin is non-toxic and easy to measure.
Thus, under steady-state conditions, the rate of inulin leaving the Bowman's capsulesmust
be exactly equal to the rate of inulin arriving in the final urine. The main idea is to measure
the amount of inulin excreted in the urine during a timeperiod were the plasma [inulin] is
maintained constant by constant infusion of inulin. After one hour the subject urinates, and
the urine volume and inulin concentration in the urine and plasma is measured. The
amount of inulin filtered through the glomerular barrier per min is: (GFR
× Cp /0.94).
All inulin molecules remain in the preurine until the subject urinates. Thus, the
amountexcreted is equal to the amount filtered and Eq. 25-4 is developed (see later).
Since the inulin clearance is 180 l per 24 hours for young, healthy males or 125 ml per
min, the GFR must be (125 × 0.94) = 118 ml per min. The inulin clearance is 10% lower
for young females than for young males due to the difference in average body weight and
body surface area.
The normal values for both sexes decrease with age to 70 ml per min after the age of 70.
Inulin clearance is a precise experimental measure and the ideal standard, but inulin must
be infused intravenously, and the method is not necessary in clinical routine.
If the clearance of a substance has the same value as the inulin clearance for the person,
then the substance is only subject to ultrafiltration. Theoretically, reabsorption might
balance tubular secretion and give the same result.
If the clearance of a substance is greater than the inulin clearance, then clearly this
substance is being added to the urine as it flows along the tubules; in other words, it is
being secreted.
Similarly, if the clearance of a substance is less than the inulin clearance, it means that the
substance is being reabsorbed at a higher rate than any possible secretion.
The extracellular fluid volume (ECV) can be measured with inulin as inulin does not pass
the cell membrane (see Chapter 24 and Eq. 24-4). The elimination of inulin is exponential -
ie, the fraction (k) of the remaining amount in the body that disappears per time unit is
constant (see Chapter 1). Since the filtration family of substances is eliminated from the
blood solely by filtration, the elimination depends only on GFR, and the distribution
volume is that of inulin (ECV). Thus, the elimination rate constant (k= 0.69/T½) for the
inulin family is roughly equal to (GFR*C p )/(ECV*Cp ).](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-48-320.jpg)
![2c. The three clearance-families
All substances treated by the kidneys can be divided into three groups or families, namely
the filtration-, the reabsorption-, and the secretion- family.
The kidney treats the filtration family of substances (see later) just like inulin.
The filtration rate (J filtr ) for inulin equals the excretion rate (J excr ), and both increase in
direct proportion to the rise in Cp (Fig. 25-5). The clearance is the slope of the curve, and
it is obviously a constant value that is independent of Cp .
Fig. 25-5:The straight line shows a direct relationship between the filtration rate and
the concentration for the inulin family of substances in plasma.
The reabsorption or glucose family contains many vital substances (see later). For the
reabsorption family of compounds, the excretion flux is equal to the filtration flux minus
the reabsorption flux. The maximal reabsorption flux (T max ) is reached above a certain
threshold. Above this saturation threshold the clearance for the reabsorption family is equal
to (the inulin clearance - Tmax /C p ), according to the mathematical argument in Fig. 25-8.
The secretion or PAH family comprises endogenous substances and drugs (see later).
Foreign substances are often distributed in the ECV, but some of them are also entering
cells (ICV). At low concentrations their elimination rate constant (k) is roughly equal to
renal plasma flow (RPF) divided by ECV: ( RPF*C P /ECV*C P ) = RPF/ECV. Thus, k
equals RPF/ECV or 1/20 min-1 in most healthy persons. The k value corresponds to a half-
life of 14 min (T ½ = ln 2/k).
2d. Excretion rate and clearance.
Excretion rate curves for inulin can be changed into clearance by a simple mathematical
procedure:
Differentiating the excretion flux curve for the inulin family with respect to Cp produce the
renal plasma clearance curves for these substances. Let us assume that the curves are from
a resting person in steady state with a normal inulin clearance (the slope of the line in Fig.
25-6,A).
For the inulin family the excretion flux equals (urine flow × Cu ), and by division with Cp
we have the inulin clearance.
Fig. 25-6: A, B, and C are the filtration-reabsorption- and secretion-families of
substances, respectively. - D shows the clearance curves.
For all substances belonging to the inulin family the excretion flux curves are linear, so the
rate of change (which is the clearance) must be constant in a given condition (Fig. 25-6A).
The results of the three excretion fluxes are plotted with Cp as the dependent variable (x-
axis of Fig. 25-6, ABC).
The excretion flux curves for the three families of substances, when differentiated
(dJ excr /dC p ), provide us with the three possible clearance curves (Fig. 25-6, D).
For the reabsorption family, the clearance is zero at first, because the excretion is zero (Fig.
25-6 D). The clearance increases, and finally it approaches the inulin clearance. Therefore,
the clearance is steadily increasing towards inulin clearance with increasing Cp .
For the secretion family, the clearance must also be equal to the excretion flux divided by
Cp . When the [PAH] increases, more and more PAH is eliminated by filtration, and the
secretory elimination is relatively suppressed (so-called auto-suppression). The clearance
for the secretion family is falling with increasing Cp , and approaches that of inulin (Fig. 25-
6 D).](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-49-320.jpg)
![and Bowman's capsule so GFR may increase. In reverse, angiotensin II secretion inhibits
the proximal reabsorption rate, increases the proximal pressure and may reduce GFR.
The total distal flow resistance below the proximal tubules (ie, in the distal system) is
large and important. The distal resistance has two major components namely a high
resistance in the Henle loop and an even higher resistance in the remaining distal system
including the collecting ducts.
The resistance of the glomerular barrier is calculated in Fig. 25-7 to be extremely small.
Normally, there is hardly any hydrodynamic resistance to glomerular ultrafiltration.
4. Tubular reabsorption and the glucose family
The reabsorption or glucose family contains vital substances such as glucose, amino acids,
albumin, acetoacetates, ascorbic acid, beta-hydroxybutyrate, carboxylate, vitamins, lactate,
pyruvate, Na+ , Cl - , HCO3 - , phosphate, sulphate and urea.
4a. Tubular handling of glucose
Tmax is the maximum transfer or net reabsorption flux (J reabs ) for glucose (mol.wt. 180 g
per mol) in the proximal tubules. The optimal value for this glucose transporter is 300
mg/min or 300/180 = 1.7 mmol/min for healthy, young subjects with a body weight of 70
kg.
For the reabsorption family of substances, the excretion is zero at first since the entire
filtered load is reabsorbed (all glucose is reabsorbed, see Fig. 25-8). The excretion flux
increases then linearly with increasing filtration flux.
Fig. 25-8: Renal Glucose rates as a function of the plasma concentration (Cp ).
The appearance threshold is the blood plasma [glucose] at which the glucose can be first
detected in the urine (normally 8.3 mM or 150 mg%). This occurs when most but not all
nephrons are saturated (Fig. 25-8).
The actual saturation threshold, the point where all nephrons are glucose-saturated, is
much higher (normally above 13.3 mM). The concentration difference (13.3 - 8.3 = 5 mM)
represents a similar reabsorption rate difference (1.7 - 1.0 = 0.7 mmol/min at normal GFR)
called splay. The reabsorption capacity for glucose in the proximal tubule cells becomes
saturated at these high blood concentrations (Fig. 25-8).
4b. Urea transport
The water reabsorption in the proximal tubules increases the urea concentration in the fluid.
Since urea is uncharged and diffuses easily, it will diffuse passively to the peritubular
capillary blood. The passage fraction at the outlet of the proximal tubule is around 0.5 (50%
of the filtered load).
Urea is thus reabsorbed in the proximal tubules and also in the inner medullary collecting
ducts and secreted in the thin descending and ascending limb of the Henle loop (see later).
The kidney reuses urea by recirculation in the intra-renal urea recycling circuit: Inner
medullary collecting ducts – medullary interstitium – loop of Henle – distal tubules –
collecting ducts.
The net reabsorption flux is around 50% of the filtration flux at normal urine flow. The
normal urea concentration in plasma is 5mM, and the excretion flux for urea is
proportional to this urea concentration.
4c. Proximal tubular reabsorption](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-52-320.jpg)
![positive charge of the tubular fluid (Fig. 25-10).
The secondary active reabsorption of Na+ (and Cl-) is the basis for the transepithelial
single effect gradient at each transverse level of the thick ascending limb (see later).
Fig. 25-10: Reabsorption of NaCl in the thick ascending limb of the Henle loop. There
is a luminal Na+ K + -2Cl- -symporter and a basolateral Na+ K + -pump. This
mechanism is essential for development of medullary hypertonicity by NaCl and thus
for counter current mutiplication (see later).
The electrochemical energy for the function of the basolateral Na+ K+ -pump is provided by
its Na+ -K+ -ATPase. The pump throws Na+ into the peritubular fluid. The K + and Cl - ions
leak out passively. The thick ascending limb is impermeable to water in the absence of
ADH, and reabsorbs Na+ actively.
Loop diuretics, which abolish the entire osmolar gradient in the outer renal medulla, inhibit
the luminal Na+ K+-2Cl - -symporter of the thick ascending limb.
4e. Reabsorption in the distal tubule and collecting duct
The distal tubule is divided into an early and a late segment, since the early segment
reabsorbs NaCl and is impermeable to water (as the thick ascending limb), whereas the late
segment functions more like the collecting duct. In the early segment, the NaCl transfer is
mediated by a NaCl-symporter (Fig. 25-11). Na+ leaves the cell through the basolateral
Na+ -K+ -pump, and Cl - leaves the cell by diffusion across the basolateral Cl - -channels.
Only a small fraction of the glomerular filtrate reaches the distal tubules. Thiazide diuretics
inhibit the NaCl-symporter.
Fig. 25-11: Cellular transport processes in the distal tubule and collecting duct.
The late segment is composed of two cell types just as the collecting ducts. The light
principal cells reabsorb Na+ and secrete K+ . The Na+ -K+ -pump in the basolateral
membrane draws Na+ out into the ISF and K+ into the principal cells (Fig. 25-11). These
cells have special ion channels in the luminal membrane, which is permeable to Na+ , but
also to K+ . The Na+ -uptake depolarises the luminal membrane (-70 mV) and makes the
lumen electronegative (-12 mV) compared to the interstitial fluid (reference potential zero).
K+ rapidly diffuses into the tubular fluid. This secretion of K+ into the tubular fluid from
the principal cell is thus linked to the Na+ -reabsorption. The amount of Na+ reabsorbed in
the distal tubule system is much less than in the proximal, but it can be increased by the
adrenocortical hormone, aldosterone. Aldosterone is a mineralocorticoid, which promotes
the reabsorption of Na+ (and thus Cl - ) and the secretion of K+ (and H+ ) in principal cells.
Aldosterone enters the cell from the blood and binds to an intracellular receptor to form a
complex. The complex increases the formation of membrane proteins including the Na+ -
K+ -pump and the luminal Na+ -channels. This is the essential control mechanism for [K+ ]
in the ECV. Secretion mainly occurs when the [K+ ] in the ECV is higher than normal.
Aldosterone also promotes the reabsorption of Na+ (and thus Cl - ) and the secretion of K+
(and H+ ) in the collecting ducts of sweat and salivary glands just as in the principal cells of
the distal tubules of the kidney. Aldosterone-antagonists inhibit all aldosterone effects. The
dark intercalated cells secrete H+ across the luminal membrane and reabsorb K+ .
Intercalated cells are mitochondrial-rich and most active in persons with a low K + -pool.
+ + +](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-54-320.jpg)
![The H -secretion by the H -pump is precisely determined by the [H ] in the ECV.
The collecting duct contains principal and intercalated cells just as the late distal segment,
but the intercalated cell disappears in the inner medullary collecting ducts.
The luminal membrane of the principal cells in the collecting ducts can be regulated from
nearly water-impermeable (in the absence of antidiuretic hormone, ADH) to water-
permeable (in the presence of ADH). The hormone increases the water-permeability by
insertion of water-channels called aquaporin 2. The water-channels are stored in
cytoplasmic vesicles that fuse with the luminal membrane. The basolateral membrane of
the principal cell contains other aquaporins and they remain water-permeable even in the
absence of ADH. Mutations in the genes for these channel proteins cause nephrogenic
diabetes insipidus.
5. Tubular secretion and the PAH family
Substances secreted like PAH constitute the secretion or PAH family. The filtration flux
(J filtr ) as usual increases in direct proportion to the rise in Cp (Fig. 25-12). Dividing the
excretion flux for PAH with Cp provides us with the PAH clearance. The clearance is the
slope of the excretion flux curve (Fig. 25-12). The secretion flux approaches a maximum
(T max ). Most of the PAH molecules are free, but 10-20% are bound to plasma proteins.
Fig. 25-12: Renal PAH net rates (fluxes or J) as a function of plasma concentration,
Cp .
Organic acids and bases secreted in the proximal tubules include endogenous substances
and drugs. The endogenous substances include adrenaline, bile salts, cAMP, creatinine,
dopamine, hippurates, noradrenaline, organic acids and bases, oxalate, prostaglandins,
steroids and urate. The drugs comprise acetazolamine, amiloride, atropine, bumetanide,
chlorothiazide, cimetidine, diodrast, furosemide, hydrochlorothiazide, morphine,
nitrofurantoin, para-aminohippuric acid (PAH), penicillin, phenol red, probenecid,
sulphonamides, and acetylsalicylic acid. The secretion is often competitive. All these
substances have varying but high affinity to an organic acid-base secretory system in the
proximal tubule cells showing saturation kinetics with a Tmax . The organic cation secretion
is analogous to the anion secretion.
5a. Tubular handling of PAH
Tmax is the maximum secretion rate for PAH in the tubules (Fig. 25-13). Normally, the
Tmax is 0.40 mmol per min (80 mg/min) for PAH.
At low PAH concentrations in the plasma (Fig. 25-13), the slope of the excretion rate
curve is high (the clearance for PAH is high). Here the PAH clearance is an acceptable
estimate of the minimal renal plasma flow (see effective RPF later), because the blood is
almost cleared by one transit.
The secretion flux is maximal, when the plasma-[PAH] is high enough to achieve
saturation. The weak organic acids and bases mentioned above are similarly secreted into
the proximal tubule, and have secretory Tmax -values just like PAH (Fig. 25-14). In
humans of average size (with an average body surface area of 1.7 m 2 ), the Tmax for
diodrast and phenol red average 57 and 36 mg/min, respectively.
5b. Tubular handling of urate
The active reabsorption of urate ions is accomplished in the proximal tubules by an
electroneutral Na+ -cotransport. The tubular reabsorptive capacity is normally far greater](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-55-320.jpg)
![towards 50 mOsmol* l-1 ). A daily solute loss of 700 mOsmol, under these conditions,
implies a daily water loss of at least 14 l.
8. Renal bloodflow (RBF)
The Fick's principle (mass balance principle) is used to measure the renal plasma clearance
at low plasma [PAH] , since at low concentrations - the blood is almost cleared by one
transit. Thus, the renal plasma clearance for PAH is almost equal to the renal plasma flow
RPF in Eq. 25-5. The law of mass balance states that the infusion rate of PAH is equal to
its excretion rate at steady state.
Only one passage through the kidneys effectively eliminates PAH from the venous blood
plasma at low [PAH]. A methodological short cut is to measure the [PAH] in the medial
cubital vein only, instead of the true arterial [PAH] by arterial catheterisation. PAH
clearance is an acceptable approximation called the effective renal plasma flow (ERPF). In
a healthy, resting person the ERPF is 600-700 ml of plasma per min and lower than the
RPF. The ERPF principle avoids complex invasive procedures such as catheterisations.
The Tmax for PAH is also a valuable measure of the secreting tubular mass, because the
proximal tubule cells are saturated with PAH at high plasma-[PAH].
The RBF falls drastically, when the mean arterial pressure is below 9.3 kPa (70 mmHg).
The medullary bloodflow is always small in both absolute and relative terms. Any severe
RBF reduction as in shock, easily leads to ischaemic damage of the medullary tissues
resulting in papillary necrosis and ultimately to failure of renal function.
During such pathophysiological conditions, prostaglandins (PGE2 and PGI2 ) are secreted
from the mesangial and endothelial cells due to sympathetic stimulation. These
prostaglandins dilatate the afferent and efferent glomerular arterioles and dampen the renal
ischaemia caused by sympatho-adrenergic vasoconstriction.
Both RBF and GFR show autoregulation following acute changes in the perfusion pressure
within the physiological pressure range (Fig. 25-15). The renal autoregulation is mediated
by myogenic feedback and by the macula densa-tubulo-glomerular feedback mechanism.
Myogenic feedback is an intrinsic property of the smooth muscle cells of the afferent and
efferent arterioles. The myogenic response allows preglomerular arterioles to sense changes
in vessel wall tension (T) and respond with appropriate adjustments in arteriolar tone.
Stretching of the cells by a rise in arterial transmural pressure (DP) elicits smooth muscle
contraction in interlobular arteries and afferent arterioles (Fig. 25-15). During sleep the
mean arterial pressure decreases 1-2 kPa, which would lower Pgc and GFR without
autoregulation. Autoregulation with maintained RBF and GFR means that also the filtered
load and the sodium excretion is maintained during sleep and variations in daily activities.
The macula densa- TGF mechanism is described below.
When the renal perfusion pressure rises, the cortical bloodflow is effectively autoregulated.
However, during certain circumstances the papillary bloodflow may increase due to release
of NO, prostaglandins, kinins or other factors. The increased medullary bloodflow
increases the interstitial hydrostatic pressure and thus the resistance towards Na+ -
reabsorption, whereby the Na+ -excretion increases.
Sympathetic vasoconstriction reduces the renal perfusion pressure and thus the resting
RBF. Increased renal sympathetic tone releases renin and enhances Na+ -reabsorption in the
proximal and distal tubules via nerve fibres. At maximum exercise RBF falls to half the
resting level. - RBF also drops during emotional stress and during haemorrhage.](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-59-320.jpg)
![distal renal tubular acidosis (ie, a bicarbonate reabsorption defect). This is a rare
inherited condition with failure of bicarbonate reabsorption in the distal tubules and
the collecting ducts. The metabolic acidosis is instituted by the oral intake of 100 mg
ammonium chloride per kg and confirmed by a pHa less than 7.35 with a negative
base excess and [bicarbonate] below 21 mM.
3. NaCl reabsorption in the early part of the distal tubule dilutes the tubular fluid,
because this segment is impermeable to water (Fig. 25-11). Thiazide diuretics inhibit
the Na+-Cl- symporter protein that causes a measurable increase in NaCl excretion
and in diuresis (Fig. 25-11).
12. Stix testing with dipstics
Routine stix testing for blood, glucose, protein etc. is necessary for the clinical evaluation
of renal patients. Reagent strips for red blood cells are extremely sensitive. Even a trivial
bleeding from a small capillary results in a positive answer indicating the presence of a few
red cells. In such cases microscopy is necessary. Microscopy of fresh urine reveals red
cells in cases of bleeding from the urinary tract, and red-cell casts in cases of kidney
bleeding as in glomerulonephritis.
Since the concentration threshold in urine for most reagent strips is 150 mg albumin per
litre (l), there is no reaction to the normal albumin concentration of 20 mg l -1 . Even 50-100
mg of protein is often excreted daily due to the upright posture and exercise.
An early sign of diabetic glomerular leakage or nephropathy is microalbuminuria, which is
defined as an albumin concentration of 50-150 mg per l of urine, and measured by
radioimmunoassay (RIA).
Some laboratories measure the Tamm-Horsefall glycoprotein, which is secreted from the
cells of the thick ascending limb of Henle, and thus a normal constituent of urine.
Bacteria in the urine produce nitrite from the urinary nitrate, and dipsticks easily
demonstrate the nitrite. Urinary tract infection also results in white blood cells in the urine,
and more than 10 cells per µl are abnormal.
13. Diuretics
Diuretics are therapeutic agents that increase the production of urine. Diuretics are
employed to enhance the excretion of salt and water in cases of cardiac oedema or arterial
hypertension. The so-called natriuretics inhibit tubular Na+ -reabsorption, but since the
secretion of K+ and H+ is also increased, the patient must have compensatory treatment.
The sites of action for different groups of diuretics are shown in Fig. 25-18.
13 a. Carboanhydrase inhibitors (eg, acetazolamide) act on the carboanhydrase (CA) in the
brush borders and inside the cells of the proximal tubules. Inhibition of the metallo-enzyme
reduces the conversion of filtered bicarbonate to carbon dioxide. As a result, there is a high
concentration of bicarbonate and sodium in the tubular fluid of the proximal tubules. Up to
half of the bicarbonate normally reabsorbed is eliminated in the urine causing a high urine
flow and a metabolic acidosis.
Thus, these inhibitors are diuretics. They are mainly used in the treatment of open-angle
glaucoma (ie, an intraocular pressure above 22 mmHg). Acetazolamide promotes the
outflow of the aqueous humour and probably diminishes its isosmotic secretion.
Fig. 25-18: Sites of action on the nephron of different groups of diuretics
13 b. Loop diuretics (bumetanide and furosemide) inhibit primarily the reabsorption of
NaCl in the thick ascending limb of Henle by blocking the luminal Na+ -K+ -2Cl - -
+](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-62-320.jpg)
![symporter. The reabsorption of NaCl, K and divalent cations is reduced, and also the
medullary hypertonicity is decreased. Hereby, the distal system receives a much higher rate
of NaCl, water in isotonic fluid, and K+ . The overall result is an increased excretion of
NaCl, water, K+ and divalent cations. The patient’s plasma- [K+ ] should be checked
regularly.
13 c. Thiazide diuretics (bendroflurazide, hydrochlorothiazide) act on the early part of the
distal tubule by inhibiting the (Na+ - Cl - )-symporter. They increase K+ excretion by
increased tubular flow rate. Thiazide and many other diuretics are secreted in the proximal
tubules. This secretion inhibits the secretion of uric acid, so thiazide is contraindicated by
gout.
13 d. Potassium-sparing diuretics (eg, amiloride) inhibit Na+ -reabsorption by inhibition of
sensitive Na+ -channels in the principal cells of the distal tubules and collecting ducts.
Hereby, they reduce the negative charge in the lumen and thus the K+ -secretion. Amiloride
causes natriuresis and reduces urinary H+ - and K+ -excretion
13 e. Aldosterone-antagonists (eg, spironolactone) compete with aldosterone for receptor
sites on principal cells. As aldosterone promotes Na+ -reabsorption and H+ / K+ -secretion,
aldosterone-antagonists cause a natriuresis and reduce urinary H+ - and K+ -excretion.
Aldosterone-antagonists are weak potassium-sparing diuretics, mainly used to reduce K + -
excretion caused by thiazide or loop diuretics.
13 f. Angiotensin-converting-enzyme (ACE)-inhibitors (captopril, enapril and lisinopril)
reversibly inhibit the production of angiotensin II, reduce systemic blood pressure, renal
vascular resistance and K+ -secretion. ACE-inhibitors promote NaCl and water excretion.
ACE-inhibitors increase RBF without much increase in GFR, because of a decrease in both
afferent and efferent arteriolar resistance. The development of diabetic nephropathy can be
markedly delayed by early reduction of blood pressure with ACE-inhibitors and by careful
diabetic management.
13 g. Osmotically active diuretics are substances such as mannitol and dextrans. These
substances retard the normal passive reabsorption of water in the proximal tubules.
Osmotic therapy with mannitol is used in the treatment of cerebral oedema.
Mannitol is a hexahydric alcohol related to mannose and an isomer of sorbitol. Mannitol
passes freely through the glomerular barrier and has hardly any reabsorption in the renal
tubules. Its presence in the tubular fluid increases flow according to the concentration of
osmotically active particles, which inhibit reabsorption of water. The high flow of tubular
fluid means that the excretion of Na+ is great - despite the rather low Na+ concentration.
Mannitol may help to flush out tubular debris in shock with acute renal failure, but the
results are controversial.
Dextrans (ie, polysaccharides) have a powerful osmotic and diuretic effect. - The larger,
molecules (macrodex) are seldom used as volume expanders during shock because of
allergic reactions.
Pathophysiology
This paragraph deals with 1. Glomerulonephritis, 2. Renal insufficiency, 3. Acute tubular
necrosis, 4. Diabetic nephropathy, 5. Nephrotic syndrome, 6. Urinary tract infection, 7.
Tubulo-interstitial nephritis, 8. Gouty nephropathy, 9. Renal hypertension, 10. Urinary
tract obstruction, and 11. Tumours of the kidney.
The severity and cause of kidney disease is evaluated by measurement of the GFR.](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-63-320.jpg)
![1. Glomerulonephritis
Glomerulonephritis is an immunologically mediated injury of the glomeruli of both
kidneys.
The majority of patients suffer from postinfectious glomerulonephritis or immune complex
nephritis. This is a disorder, where circulating antigen-antibody complexes are deposited
in the glomeruli or free antigen is bound to antibodies trapped in the capillary network.
Typically, the antigen is derived from Lancefield group Aß- haemolytic streptococci, but
also other bacteria, viruses, parasites (malaria), and drugs may be the origin. A few patients
produce antibodies against their own antigens (eg, host DNA in systemic lupus
erythematosus, malignant tumour antigen, or anti-glomerular basement antibody, anti-
GBM).
The inflammation is an abnormal immune reaction often caused by repeated streptococcal
tonsillitis. An insoluble antigen-antibody complex precipitates in the basement membrane
of the glomerular capillaries. The cells of the glomeruli proliferate, and disease will of
course reduce GFR and to some extent, the RBF (measured as PAH clearance). Thus the
infection depresses the glomerular filtration fraction (GFF = GFR/RPF).
The acute postinfectious glomerulonephritis occurs typically in a child, who has suffered
from streptococcal tonsillitis a few weeks before.
Haematuria, proteinuria, and oliguria characterise acute nephritis with salt-water retention
causing oedemas and hypertension. Pulmonary oedema and hypertensive encephalopathy
with fits is life threatening.
Uraemia is a clinical syndrome dominated by retention of non-protein nitrogen (eg, urea,
uric acid, NH 4 + creatinine and creatine). Uraemic patients generally exhibit hyperkalaemia
(plasma- [K+ ] above 5.5 mM) and metabolic acidosis (pH below 7.35 and a negative base
excess). This is due to the inadequate secretion of K+ , NH 4 + and H+ . In complete renal
shutdown, the patient dies within 1-2 weeks without dialysis.
Dialysis is mandatory with severe uraemia. When serum creatinine rises above 0.7 mM,
renal insufficiency is usually terminal (Fig. 25-4).
Recording of blood pressure and fluid balance with weighing is important in order to
prevent hypertension and pulmonary oedema to develop into a life-threatening condition.
Fig. 25-19: Post-streptococcal glomerulonephritis.
The parietal and visceral epithelial cells of the glomeruli grow and proliferate, just as the
mesangial cells (Fig. 25-19). This proliferation and the damage of the basement membrane
with accumulation of insoluble complexes all impair the glomerular barrier and reduce the
glomerular filtration rate (GFR). Production of cytokines and autocoids enhance the
inflammation. Capillary injuries with reduction of the lumen also reduce the renal
bloodflow (RBF) to some extent (Fig. 25-19).
Children with poststreptococcal glomerulonephritis are treated with a course of penicillin -
often with an excellent prognosis.
Glomerulonephritis as a part of systemic lupus erythematosus (SLE) is frequent in female
lupus patients - in particular during pregnancy, where hypertension may precipitate
glomerular injuries. Oestrogens accelerate progression of SLE, and there is a genetic
predisposition. In SLE there is hyperactivity of the B-cell system, which may involve any
organ, but typically affects the kidneys, joints, serosal membranes and the skin (Chapter
32). The B-cell system releases many antibodies to host antigens both in and outside the
cell nuclei (single- and double-stranded DNA, RNA, plasma proteins, cell surface](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-64-320.jpg)
![Wall: Strictures of the ureter, the ureterovesical region, urethra, and pinhole
meatus.
Congenital disorders such as megaureter, bladder neck obstruction, and urethral
valve.
Neuromuscular dysfunction in the urinary tract
Pressure: Compression by tumours, aortic aneurysm, retroperitoneal fibrosis or
gland enlargement, retrocaval ureter, prostate hypertrophy, phimosis, and
diverticulitis.
Two complications to chronic renal failure must be considered:
1. Renal osteodystrophy develops in patients with severe renal failure. The kidneys fail in
producing sufficient 1,25-dihydroxy-cholecalciferol. This is active vitamin D or a potent
steroid hormone. The active vitamin D metabolite stimulates the Ca2+-transport across
the cell and mitochondrial membranes.
Lack of active vitamin D has the following two effects:
a. Poor gut absorption of dietary Ca2+, so that plasma [Ca2+] falls.
b.The PTH release is stimulated, because the normal inhibitory effect of active vitamin D is
lost.
After some time a secondary hyperparathyroidism develops with increased resorption of
calcium from bone and increased proximal tubular reabsorption of calcium in an attempt
to correct the low serum calcium. The calcium release from bone results in osteomalacia
and in osteoporosis. Osteomalacia or soft bones is the result of demineralisation of the
osteoid matrix usually caused by insufficient active vitamin D. Osteoporosis or thin
bones is characterized by a reduction in all components of the bones.
2. Normochromic, normocytic anaemia. When normal kidneys are perfused with
hypoxaemic blood, the peritubular interstitial cells produce large amounts of the
glycoprotein hormone, erythropoietin, with strong effect on erythrogenesis.
Chronic renal failure leads to erythropoietin deficiency, and thus to anaemia, which is of
the normochromic, normocytic type.
Haemodialysis
The aim of haemodialysis is to eliminate nitrogenous wastes in patients with renal failure,
and maintain normal electrolyte concentrations, serum glucose and normal ECV. In other
words, the haemodialyzer or artificial kidney mimics the normal renal excretion of waste
products (Fig. 25-21)
Fig. 25-21: An artificial kidney (dialyser) with an area of 1 m 2 and a membrane
thickness of 10 µm.
Blood from the patient is pumped through a container with series of semi-permeable
membranes separating the blood from dialysate (Fig. 25-21).
Dialysate is a mixture of purified water with salts, and glucose in a composition
comparable to normal fasting plasma apart from proteins. Bicarbonate or acetate buffer is
present at a concentration about 35 mM.
Haemodialysis is performed with a bloodflow of 200-300 ml per min. The patient is often
connected to the dialyzer by an arteriovenous shunt made by plastic cannulae between the
radial artery and an adjacent vein. The arterial blood flows into the artificial kidney and
after dialysis the blood is returned to the venous system (Fig. 25-21). Dialysate is pumped
through the container at a rate of 500 ml each min.](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-66-320.jpg)
![Haemangiomas may bleed following trauma and cause fatal blood loss.
Malignant renal tumours are nephroblastoma and renal cell carcinoma.
Nephroblastoma (Wilms´ tumour) is the most frequent intraabdominal tumour in both girls
and boys. It usually presents within the first three years of life. A large abdominal mass is
found sometimes with signs of intestinal obstruction. The tumour grows rapidly and spread
to the lungs. The diagnosis is confirmed with excretion urography, arteriography or
scanning.
Radiotherapy and chemotherapy, combined with nephrectomy have improved the long-
term survival rate.
Renal cell carcinoma (hypernephroma) accounts for more than 90% of all the malignant
renal tumours in adults - in particular smokers. There is a strong association with a rare
autosomal dominant inherited disease called Von Hippel-Lindau´ syndrome
(haemangioblastomas in the cerebellum and the retina). The genetic locus is on
chromosome 3p.The tumour arises from proximal tubular epithelium, and lies within the
kidney, but the prognosis is worse, if the tumour penetrates the renal capsule. The tumour
is often protruding and the neoplastic cells have an unusually clear cytoplasm.
Renal cell carcinoma is a likely source of ectopic hormone production. Increased
production of erythropoietin leads to erythrocytosis and polycythaemia. Release of a
parathyroid-hormone-like substance leads to hyperparathyroidism and hypercalcaemia.
Release of abnormal quantities of renin triggers the renin-angiotensin-aldosterone cascade
and leads to systemic hypertension.
Metastases to distant regions are frequently found in the lungs and in the bones (osteolytic
metastases). Solitary tumours are treated by partial or total nephrectomy or with interferon.
Equations
• The plasma clearance is defined as follows:
Eq. 25-1: Clearance = (Cu ×V° u ) /C p [(mg/ml)×(ml/min)/(mg/ml)=
ml/min].
Clearance can also be thought of as the volume of arterial plasma containing the same
amount of substance as contained in the urine flow per minute.
• Excretion fraction (EF). EF for a substance is the fraction of its glomerular filtration
flux, which passes to and is excreted in the urine.
EF = J excr /J filtr
Since J excr = (Cu ×V° u ) and J filtr =(GFR × Cfiltr ) it follows that:
Eq. 25-2: EF = (Cu ×V° u ) /(GFR × Cfiltr )
Cfiltr is the concentration of the substance in the ultrafiltrate. The excretion fraction for
inulin is one (1). Substances with an EF above one are subject to net secretion. Substances
with an EF below one are subject to net reabsorption.
• Extraction fraction (E). E for a substance is the fraction extracted by glomerular
filtration from the total substance delivery to the kidney via renal blood plasma.
Eq. 25-3: E = J filtr /J total = (Ca - Cvr)/C a.
Substances with an E of one are cleared totally from the plasma during their first passage
of the kidneys. Inulin has an extraction fraction of 1/5. PAH has an extraction fraction of
0.9.](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-72-320.jpg)
![• Inulin clearance. The flux of inulin filtered through the glomerular barrier per min is:
(GFR × Cp /0.94). All inulin molecules remain in the preurine and is excreted in the
final urine.
Thus, the amount excreted is equal to the amount filtered:
GFR × Cp /0,94 = (Cu ×V° u ) mmol/min
Eq. 25-4: GFR = ((C u ×V° u ) /C p ) × 0.94 = CLEARANCEinulin × 0.94.
• The Fick's principle (mass balance principle) is used to measure the renal plasma
clearance at low plasma [PAH], since at low concentrations the blood is almost
cleared (90%) by one transit. Thus the renal plasma clearance is equal to the effective
renal plasma flow (ERPF):
Eq. 25-5: ERPF = J excr /Cp ; RPF = ERPF/E PAH
• The law of mass balance states that the delivery of PAH to the kidney is equal to its
excretion rate at steady state. The Effective Renal Blood Flow (ERBF) is calculated by
the help of a total body haematocrit (normally 0.45). If ERPF is measured to be 600 ml
plasma per min, we can calculate ERBF: 600/(1 - 0.45) = 1090 ml whole blood per min
at rest. This is 20-25 % of cardiac output. The true RBF is 10% higher than the
measured ERBF (ie, 1200 compared to 1090 ml whole blood).
Self-Assessment
Multiple Choice Questions
The following five statements have True/False options:
A: The B-cell system releases antibodies to host antigens.
B: The glomerular barrier facilitates the passage of negatively charged polyanionic
macromolecules.
C: Thiazide diuretics may have serious side effects such as hypercholesterolaemia,
hyperglycaemia (eg, glucose intolerance), hyperuricaemia, hypokalaemia, and
impotence.
D: Loop diuretics inhibit the reabsorption of NaCl in the thick ascending limb of Henle –
and proximal pars recta - by blocking the cotransport process in the luminal entry
membrane.
E: Aldosterone antagonists, such as spironolactone, act on the aldosterone receptors on the
late distal tubule cell and inhibit the K + -excretion.
Case History A
A male office worker, 58 years of age, body weight 70 kg, suffers from insulin-dependent
diabetes mellitus. The disorder is complicated with arterial hypertension,
hypercholesterolaemia, albuminuria and open-angle glaucoma. The patient is in anti-
hypertensive therapy with a ß-adrenergic antagonist. The open-angle glaucoma is treated
with acetazolamide (a carboanhydrase-inhibitor used as a diuretic to reduce the intra-
ocular pressure).
Scanning of the kidneys show a normal picture with an estimated normal kidney weight of
300 g. During renal catheterisation, a renal arteriovenous oxygen content difference is
measured to 15 ml per l of blood, and the renal bloodflow is 1.2 l (normal). – The first 3
questions necessitate pharmacological knowledge.
1. Is it recommendable to treat hypertensive complications to diabetes with ß-blockers?
2. Describe the effects of carboanhydrase-inhibitor- treatment.](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-73-320.jpg)
![3. Are thiazide diuretics without risks when prescribed to diabetics?
4. Calculate the renal oxygen uptake. Calculate the renal oxygen uptake in percentage
of the total oxygen uptake of 250 ml per min.
5. Calculate the kidney weight in percentage of the total body weight.
6. Is the renal bloodflow redundant compared to the renal oxygen consumption?
Case History B
A female patient (weight 57-kg) of 23 years, with an inherited defect in renal tubular
function, has a lowered tubular threshold for glucose reabsorption. The patient has a
blood- [glucose] of 1000 mg per litre, and just above this level glucose appears in the
urine (her appearance threshold). The diuresis is 1.5 ml per min, the plasma -[creatinine]
is 0.09 mM, and the urine [creatinine] is 6 mM. The normal blood-glucose level is 5-6 mM.
1. Is the above blood -[glucose] normal?
2. Calculate the creatinine clearance?
3. Calculate the glucose reabsorption at this glucose level and compare it to the normal
maximal capacity: 1.78 mmol min-1 .
4. Is the appearance threshold defined above equal to the saturation threshold?
Case History C
A 14-year old girl has a history of previous upper respiratory tract infections, and is now
treated for another sore throat (ie, tonsillitis and high fever) with ampicillin for 10 days.
Two weeks later she returns to her general practitioner (GP) complaining of tender knee
joints from playing handball. There is abdominal pain.
The girl is obviously ill and has a higher blood pressure than normally (145/90 mmHg or
19.3/12.7 kPa). The tonsillitis is cured and there is no fever. The upper abdomen is tender.
A freshly passes urine sample is examined with a combined quantitative stick test. There is
found haematuria and albuminuria (300 mg l -1 ).
1. What is the cause of the arthritis?
2. What are the causes of the haematuria and albuminuria?
3. Does the GP admit the girl to a hospital?
Case History D
During her working hours a 24-year old nurse delivered an arterial sample for blood gas
tensions. She had no symptoms or signs of disease, but doubted that an arterial sample
could be taken without causing pain. The sample was taken from a radial artery with a fine
needle following local anaesthesia and she experienced no pain. The arterial blood gas
values were: CO 2 partial pressure 24 mmHg, O2 partial pressure 102 mmHg, pHa 7.36,
and Base Excess - 8 mM. The nurse had been starving for 24 hours.
1. What was the explanation of her acid-base disturbance?
2. What was the rational treatment?
Case History E
A young female (body weight 56 kg) with an inulin clearance of 125 ml of plasma per min
is tested with para-amino-hippuric acid (PAH). The free fraction of PAH in the plasma is](https://image.slidesharecdn.com/40bun-091212023232-phpapp01/85/4-0-Bun-74-320.jpg)
4 0 Bun
- 1. Skip navigation Other encyclopedia articles: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 0-9 Comprehensive metabolic panel A comprehensive metabolic panel is a group of chemical tests performed on the blood MedlinePlus Topics serum (the part of blood that doesn't contain cells). Laboratory Tests These tests include total cholesterol, total protein, and various electrolytes. Electrolytes in the body include sodium, potassium, chlorine, and many others. Read More Electrolytes The rest of the tests measure chemicals that reflect liver and kidney function. How the Test is Performed A blood sample is needed. For information on giving a blood sample from a vein, see venipuncture. How to Prepare for the Test You should not eat or drink for 8 hours before the test. How the Test Will Feel When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. Why the Test is Performed This test helps provide information about your body's metabolism. It give your doctor information about how your kidneys and liver are working, and can be used to evaluate blood sugar, cholesterol, and calcium levels, among other things. Your doctor may order this test during a yearly exam or routine check up. Normal Results Albumin: 3.9 to 5.0 g/dL Alkaline phosphatase: 44 to 147 IU/L ALT (alanine transaminase): 8 to 37 IU/L AST (aspartate aminotransferase): 10 to 34 IU/L BUN (blood urea nitrogen): 7 to 20 mg/dL Calcium - serum: 8.5 to 10.9 mg/dL Serum chloride: 101 to 111 mmol/L CO2 (carbon dioxide): 20 to 29 mmol/L Creatinine: 0.8 to 1.4 mg/dL ** Direct bilirubin: 0.0 to 0.3 mg/dL Gamma-GT (gamma-glutamyl transpeptidase): 0 to 51 IU/L Glucose test: 64 to 128 mg/dL LDH (lactate dehydrogenase): 105 to 333 IU/L Phosphorus - serum: 2.4 to 4.1 mg/dL
- 2. Potassium test: 3.7 to 5.2 mEq/L Serum sodium: 136 to 144 mEq/L Total bilirubin: 0.2 to 1.9 mg/dL Total cholesterol: 100 to 240 mg/dL Total protein: 6.3 to 7.9 g/dL Uric acid: 4.1 to 8.8 mg/dL **Note: Normal or “healthy” values for creatinine can vary with age. Normal value ranges for all tests may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results. Key to abbreviations: IU = international unit L = liter dL = deciliter = 0.1 liter g/dL = gram per deciliter mg = milligram mmol = millimole mEq = milliequivalents What Abnormal Results Mean Abnormal results can be due to a variety of different medical conditions, including kidney failure, breathing problems, and diabetes-related complications. See the individual tests listed in the normal values section for detailed information. Risks There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others. Other risks associated with having blood drawn are slight but may include: Excessive bleeding Fainting or feeling light-headed Hematoma (blood accumulating under the skin) Infection (a slight risk any time the skin is broken) Alternative Names Metabolic panel - comprehensive; Chem-20; SMA20; Sequential multi-channel analysis with computer-20; SMAC20; Metabolic panel 20 Update Date: 2/23/2009 Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch). The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 1997-2009, A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
- 3. Skip navigation Other encyclopedia articles: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 0-9 BUN BUN stands for blood urea nitrogen. Urea nitrogen is what forms when protein breaks MedlinePlus Topics down. Kidney Diseases A test can be done to measure the amount of urea nitrogen in the blood. Read More How the Test is Performed Acute bilateral obstructive uropathy Acute kidney failure Acute tubular necrosis Blood is typically drawn from a vein, usually from the inside of the elbow or the back of Amino acids the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care Ammonium ion provider wraps an elastic band around the upper arm to apply pressure to the area and Gastrointestinal bleeding make the vein swell with blood. Glomerulonephritis Heart attack Next, the health care provider gently inserts a needle into the vein. The blood collects Heart failure into an airtight vial or tube attached to the needle. The elastic band is removed from your Hypovolemic shock arm. Kidney disease Metabolism Once the blood has been collected, the needle is removed, and the puncture site is Renal covered to stop any bleeding. Shock In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding. How to Prepare for the Test Many drugs affect BUN levels. Before having this test, make sure the health care provider knows which medications you are taking. Drugs that can increase BUN measurements include: Allopurinol Aminoglycosides Amphotericin B Aspirin (high doses) Bacitracin Carbamazepine Cephalosporins Chloral hydrate Cisplatin Colistin Furosemide Gentamicin Guanethidine Indomethacin Methicillin Methotrexate Methyldopa
- 4. Neomycin Penicillamine Polymyxin B Probenecid Propranolol Rifampin Spironolactone Tetracyclines Thiazide diuretics Triamterene Vancomycin Drugs that can decrease BUN measurements include: Chloramphenicol Streptomycin How the Test Will Feel When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. Why the Test is Performed The BUN test is often done to check kidney function. Normal Results 7 - 20 mg/dL. Note that normal values may vary among different laboratories. What Abnormal Results Mean Higher-than-normal levels may be due to: Congestive heart failure Excessive protein levels in the gastrointestinal tract Gastrointestinal bleeding Hypovolemia Heart attack Kidney disease, including glomerulonephritis, pyelonephritis, and acute tubular necrosis Kidney failure Shock Urinary tract obstruction Lower-than-normal levels may be due to: Liver failure Low protein diet Malnutrition Over-hydration Additional conditions under which the test may be done include: Acute nephritic syndrome Alport syndrome Atheroembolic kidney disease Dementia due to metabolic causes
- 5. Diabetic nephropathy/sclerosis Digitalis toxicity Epilepsy Generalized tonic-clonic seizure Goodpasture syndrome Hemolytic-uremic syndrome (HUS) Hepatokidney syndrome Interstitial nephritis Lupus nephritis Malignant hypertension (arteriolar nephrosclerosis) Medullary cystic kidney disease Membranoproliferative GN I Membranoproliferative GN II Type 2 diabetes Prerenal azotemia Primary amyloidosis Secondary systemic amyloidosis Wilms' tumor Risks Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. Other risks are slight but may include: Excessive bleeding Fainting or feeling light-headed Hematoma (blood accumulating under the skin) Infection (a slight risk any time the skin is broken) Considerations For people with liver disease, the BUN level may be low even if the kidneys are normal. Alternative Names Blood urea nitrogen References Molitoris BA. Acute kidney injury. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 121. Update Date: 5/13/2009 Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding
- 6. 07. Creatinine Primary function of kidney : excrete unwanted materials, retain those chemicals necessary for proper function 1. passive excretion (glomerular filtration) 2. reabsorption from the tubule back into the circulation 3. secretion from the circulation into the tubule Excretion capacity°¡ kidney function Æò°¡¿¡ ÁÖ ¿äÀÎ. ExcretionÀº ȯÀÚÀÇ (blood stream> administered substanceÀÇ) renal clearance Æò°¡·Î ÀÌ·ç¾îÁú ¼ö ÀÖÀ½. skeletal muscle¿¡¼ creatine phosphate --------> creatinine + H2PO4- + H+ creatine --------> creatinine + H2O (plasma·Î constantÇÏ°Ô release) --------> glomerular filtrate¿¡ Á¸Àç (tubular reabsorptionÀÌ °ÅÀÇ ¾ø´Ù) glomerular filtration rate(GFR)°¡ °¨¼ÒÇϸé ü¿Ü·Î excretion ÀÌ °¨¼ÒµÇ°í serum³» ³óµµ°¡ ³ô¾ÆÁü. -----> renal glomerular functionÀÇ ÁöÇ¥. creatinineÀÇ outputÀº total body mass º¸´Ù´Â muscle mass¿¡ ´õ ÀÇÁ¸ 1) Assay method Jaffe reaction OH -(0.1 M NaOH) creatinine + picrate ------------------> red colored complex(A 520 nm) ±¸Á¶´Â ¸ð¸§ i) sample Áß¿¡¼ protein Á¦°Å (proteinÀÌ picrate¿Í ¹ÝÀÀ) ii) constant Temp.À¯Áö : 30 C ÀÌÇÏ·Î À¯Áö, ÀÌ»óÀÏ °æ¿ì ´Ù¸¥ compound°¡ picrate¿Í ¹ÝÀÀ iii) time is a significance factor : incubation timeÀ» ´Ã¸®¸é nonspecific colored products°¡ ´Ã¾î³² ÀÌ·¯ÇÑ interference¸¦ ÁÙÀ̱â À§ÇØ enzyme method°¡ ½Ãµµ Áß creatinine iminohydrolase¿¡ ÀÇÇØ ammonium ionÀÌ µÇ¾î colorimetry ¶Ç´Â ion-selective electrode »ç¿ë. specimen : serum, plasma, urine(1:200 dilution ÇÊ¿ä) 2) Clinical significance * serum ³» creatinine Áõ°¡ : renal damage
- 7. creatinine °¨¼Ò : no significance 0.9-1.5 mg/dL (men) > 0.7-1.3 mg/dL (women) serum creatinine ÃøÁ¤ÈÄ ÇÊ¿ä½Ã Creatinine clearance : renal functionÀ» assayÇϴµ¥ sensitiveÇÑ ¹æ¹ý. glomerular filtration rate(GFR)¸¦ ÃøÁ¤ 24 hrÀÇ urine °ú blood sample äÃë UV 1.73 creatinine clearance(ml/min) = ----- X ----- P S U : urinary creatinine (mg/L) V : volume of urine (ml/min) P : plasma creatinine (mg/L) S : surface area of patient 1.73 : standard 70 kgÀÇ surface area¸¦ 1.73 Reference range : 95-140 ml/min (man), 90-130 ml/min (woman) creatinine clearance Áõ°¡ : no significance creatinine clearance °¨¼Ò : glomerular filtration rateÀÇ ÀúÇÏ
- 9. Blood sugar From Wikipedia, the free encyclopedia Blood sugar concentration, or glucose level, refers to the amount of glucose present in the blood of a human or animal. Normally, in mammals the blood glucose level is maintained at a reference range between about 3.6 and 5.8 mM (mmol/l). It is tightly regulated as a part of metabolic homeostasis. Mean normal blood glucose levels in humans are about 90 mg/dl, equivalent to 5mM (mmol/l) (since the molecular weight of glucose, C6H12O6, is about 180 g/mol). The total amount of glucose normally in circulating human blood is therefore about 3.3 to 7g (assuming an ordinary adult blood volume of 5 litres, plausible for an average adult male). Glucose levels rise after meals for an hour or two by a few grams and are usually lowest in the morning, before the first meal of the day. Transported via the bloodstream from the intestines or liver to body cells, glucose is the primary source of energy for body's cells, fats and oils (ie, lipids) The fluctuation of blood sugar (red) and the sugar-lowering hormone being primarily a compact energy store. insulin (blue) in humans during the course of a day with three meals. One of the effects of a sugar-rich vs a starch-rich meal is highlighted. Failure to maintain blood glucose in the normal range leads to conditions of persistently high (hyperglycemia) or low (hypoglycemia) blood sugar. Diabetes mellitus, characterized by persistent hyperglycemia from any of several causes, is the most prominent disease related to failure of blood sugar regulation. Contents 1 Normal values 2 Regulation 3 Glucose measurement 3.1 Sample type 3.2 Measurement techniques 3.3 Blood glucose laboratory tests 3.4 Clinical correlation 4 Health effects 5 Low blood sugar 6 Converting glucose units 7 Comparative content 8 Etymology and use of term 9 Blood glucose in birds and reptiles 10 References 11 See also Normal values Despite widely variable intervals between meals or the occasional consumption of meals with a substantial carbohydrate load, human blood glucose levels normally remain within a remarkably narrow range. In most humans this varies from about 82 mg/dl to perhaps 110 mg/dl (4.4 to 6.1 mmol/l) except shortly after eating when the blood glucose level rises temporarily up to maybe 140 mg/dl (7.8 mmol/l) or a bit more in non-diabetics. The American Diabetes Association recommends a post-meal glucose level less than 180 mg/dl (10 mmol/l) and a pre-meal plasma glucose of 90-130 mg/dl (5 to 7.2 mmol/l). [1] It is usually a surprise to realize how little glucose is actually maintained in the blood and body fluids. The control mechanism works on very small quantities. In a healthy adult male of 75 kg (165 lb) with a blood volume of 5 litres (1.3 gal), a blood
- 10. glucose level of 100 mg/dl or 5.5 mmol/l corresponds to about 5 g (0.2 oz or 0.002 gal, 1/500 of the total) of glucose in the blood and approximately 45 g (1½ ounces) in the total body water (which obviously includes more than merely blood and will be usually about 60% of the total body weight in men). A more familiar comparison may help – 5 grams of glucose is about equivalent to a small sugar packet as provided in many restaurants with coffee or tea, with people using typically 1 to 3 packets per cup. Regulation Main article: Blood sugar regulation The homeostatic mechanism which keeps the blood value of glucose in a remarkably narrow range is composed of several interacting systems, of which hormone regulation is the most important. There are two types of mutually antagonistic metabolic hormones affecting blood glucose levels: catabolic hormones (such as glucagon, growth hormone, cortisol and catecholamines) which increase blood glucose; and one anabolic hormone (insulin), which decreases blood glucose. Glucose measurement Main article: Blood glucose monitoring Sample type Glucose can be measured in whole blood or serum (ie, plasma). Historically, blood glucose values were given in terms of whole blood, but most laboratories now measure and report the serum glucose levels. Because red blood cells (erythrocytes) have a higher concentration of protein (eg, hemoglobin) than serum, serum has a higher water content and consequently more dissolved glucose than does whole blood. To convert from whole-blood glucose, multiplication by 1.15 has been shown to generally give the serum/plasma level. Collection of blood in clot tubes for serum chemistry analysis permits the metabolism of glucose in the sample by blood cells until separated by centrifugation. Red blood cells, for instance, do not require insulin to intake glucose from the blood. Higher than normal amounts of white or red blood cell counts can lead to excessive glycolysis in the sample with substantial reduction of glucose level if the sample is not processed quickly. Ambient temperature at which the blood sample is kept prior to centrifuging and separation of plasma/serum also affects glucose levels. At refrigerator temperatures, glucose remains relatively stable for several hours in a blood sample. At room temperature (25 °C), a loss of 1 to 2% of total glucose per hour should be expected in whole blood samples. Loss of glucose under these conditions can be prevented by using Fluoride tubes (ie, gray-top) since fluoride inhibits glycolysis. However, these should only be used when blood will be transported from one hospital laboratory to another for glucose measurement. Red-top serum separator tubes also preserve glucose in samples after being centrifuged isolating the serum from cells. Particular care should be given to drawing blood samples from the arm opposite the one in which an intravenous line is inserted, to prevent contamination of the sample with intravenous fluids. Alternatively, blood can be drawn from the same arm with an IV line after the IV has been turned off for at least 5 minutes, and the arm elevated to drain infused fluids away from the vein. Inattention can lead to large errors, since as little as 10% contamination with 5% dextrose (D5W) will elevate glucose in a sample by 500 mg/dl or more. Remember that the actual concentration of glucose in blood is very low, even in the hyperglycemic. Arterial, capillary and venous blood have comparable glucose levels in a fasting individual. After meals venous levels are somewhat lower than capillary or arterial blood; a common estimate is about 10%. Measurement techniques Two major methods have been used to measure glucose. The first, still in use in some places, is a chemical method exploiting the nonspecific reducing property of glucose in a reaction with an indicator substance that changes color when reduced. Since other blood compounds also have reducing properties (e.g., urea, which can be abnormally high in uremic patients), this technique can produce erroneous readings in some situations (5 to 15 mg/dl has been reported). The more recent technique, using enzymes specific to glucose, are less susceptible to this kind of error. The two most common employed enzymes are
- 11. glucose oxidase and hexokinase. In either case, the chemical system is commonly contained on a test strip, to which a blood sample is applied, and which is then inserted into the meter for reading. Test strip shapes and their exact chemical composition vary between meter systems and cannot be interchanged. Formerly, some test strips were read (after timing and wiping away the blood sample) by visual comparison against a color chart printed on the vial label. Strips of this type are still used for urine glucose readings, but for blood glucose levels they are obsolete. Their error rates were, in any case, much higher. Urine glucose readings, however taken, are much less useful. In properly functioning kidneys, glucose does not appear in urine until the renal threshold for glucose has been exceeded. This is substantially above any normal glucose level, and so is evidence of an existing severe hyperglycemic condition. However, urine is stored in the bladder and so any glucose in it might have been produced at any time since the last time the bladder was emptied. Since metabolic conditions change rapidly, as a result of any of several factors, this is delayed news and gives no warning of a developing condition. Blood glucose monitoring is far preferable, both clinically and for home monitoring by patients. I. CHEMICAL METHODS A. Oxidation-Reduction Reaction 1. Alkaline Copper Reduction Folin Wu Blue end- Method product Benedict's Modification of Folin wu for Qualitative Urine Glucose method Nelson Somoygi Blue end- Method product Yellow- Neocuproine * orange color Method Neocuproine Shaeffer Utilizes the principle of Iodine reaction with Cuprous byproduct. Hartmann Excess I2 is then titrated with thiosulfate. Somygi 2. Alkaline Ferricyanide Reduction Colorless end product; other Hagedorn reducing Jensen substances interfere with reaction B. Condensation Utilizes aromatic amines and hot acetic acid Ortho-toluidine Forms Glycosylamine and Schiff's base which is emerald green in color Method This is the most specific method, but the reagent used is toxic Anthrone (Phenols) Forms hydroxymethyl furfural in hot acetic acid Method II. ENZYMATIC METHODS A. Glucose Oxidase Inhibited by
- 12. reducing substances Saifer like BUA, Gernstenfield Bilirubin, Method Glutathione, Ascorbic Acid uses 4-aminophenazone oxidatively coupled with Phenol Trinder Method Subject to less interference by increases serum levels of Creatinine, Uric Acid or Hemoglobin Inhibited by Catalase A Dry Chemistry Method Kodak Uses Reflectance Spectrophotometry to measure the intensity of color through a lower transparent Ektachem film Home monitoring blood glucose assay method Glucometer Uses a strip impregnated with a Glucose Oxidase reagent B. Hexokinase NADP as cofactor NADPH (reduced product) is measured in 340 nm More specific than Glucose Oxidase method due to G-6PO_4, which inhibits interfering substances except when sample is hemolyzed Blood glucose laboratory tests 1. fasting blood sugar (ie, glucose) test (FBS) 2. urine glucose test 3. two-hr postprandial blood sugar test (2-h PPBS) 4. oral glucose tolerance test (OGTT) 5. intravenous glucose tolerance test (IVGTT) 6. glycosylated hemoglobin (HbA1C) 7. self-monitoring of glucose level via patient testing Clinical correlation The fasting blood glucose (FBG) level is the most commonly used indication of overall glucose homeostasis, largely because disturbing events such as food intake are avoided. Conditions affecting glucose levels are shown in the table below. Abnormalities in these test results are due to problems in the multiple control mechanism of glucose regulation. The metabolic response to a carbohydrate challenge is conveniently assessed by a postprandial glucose level drawn 2 hours after a meal or a glucose load. In addition, the glucose tolerance test, consisting of several timed measurements after a standardized amount of oral glucose intake, is used to aid in the diagnosis of diabetes. It is regarded as the gold standard of clinical tests of the insulin / glucose control system, but is difficult to administer, requiring much time and repeated blood tests. Note that food commonly includes carbohydrates which don't participate in the metabolic control system; simple sugars such as fructose, many of the disaccarhides (which either contain simple sugars other than glucose or cannot be digested by humans) and the more complex sugars which also cannot be digested by humans. And there are carbohydrates which are not digested even with the assistance of gut bacteria; several of the fibres (soluble or insoluble) are chemically carbohydrates. Food also commonly contains components which affect glucose (and other sugar's) digestion; fat, for example slows down digestive processing, even for such easily handled food constituents as starch. Avoiding the effects of food on blood glucose measurement is important for reliable results since those effects are so variable.
- 13. Error rates for blood glucose measurements systems vary, depending on laboratories, and on the methods used. Colorimetry techniques can be biased by color changes in test strips (from airborne or finger borne contamination, perhaps) or interference (eg, tinting contaminants) with light source or the light sensor. Electrical techniques are less susceptible to these errors, though not to others. In home use, the most important issue is not accuracy, but trend. Thus if your meter / test strip system is consistently wrong by 10%, there will be little consequence, as long as changes (eg, due to exercise or medication adjustments) are properly tracked. In the US, home use blood test meters must be approved by the Federal Food and Drug Administration before they can be sold. Similar supervision is imposed in other jurisdictions. Finally, there are several influences on blood glucose level aside from food intake. Infection, for instance, tends to change blood glucose levels, as does stress either physical or psychological. Exercise, especially if prolonged or long after the most recent meal, will have an effect as well. In the normal person, maintenance of blood glucose at near constant levels will nevertheless be quite effective. Causes of Abnormal Glucose Levels Persistent Hyperglycemia Transient Hyperglycemia Persistent Hypoglycemia Transient Hypoglycemia Reference Range, FBG: 70-110 mg/dl Diabetes Mellitus Pheochromocytoma Insulinoma Acute Alcohol Ingestion Adrenal cortical hyperactivity Adrenal cortical insufficiency Drugs: salicylates, Severe Liver Disease Cushing's Syndrome Addison's Disease antituberculosis agents Hyperthyroidism Acute stress reaction Hypopituitarism Severe Liver disease Several Glycogen storage Acromegaly Shock Galactosemia diseases Ectopic Insulin production Hereditary fructose Obesity Convulsions from tumors intolerance Health effects If blood sugar levels drop too low, a potentially fatal condition called hypoglycemia develops. Symptoms may include lethargy, impaired mental functioning, irritability, shaking, weakness in arm and leg muscles, sweatting and loss of consciousness. Brain damage is even possible. If levels remain too high, appetite is suppressed over the short term. Long-term hyperglycemia causes many of the long-term health problems associated with diabetes, including eye, kidney, heart disease and nerve damage. Low blood sugar Some people report drowsiness or impaired cognitive function several hours after meals, which they believe is related to a drop in blood sugar, or "low blood sugar". For more information, see: idiopathic postprandial syndrome hypoglycemia Mechanisms which restore satisfactory blood glucose levels after hypoglycemia must be quick and effective, because of the immediately serious consequences of insufficient glucose; in the extreme, coma, but also less immediately dangerous, confusion or unsteadiness, amongst many other symptoms. This is because, at least in the short term, it is far more dangerous to have too little glucose in the blood than too much. In healthy individuals these mechanisms are generally quite effective, and symptomatic hypoglycemia is generally only found in diabetics using insulin or other pharmacological treatment. Such hypoglycemic episodes vary greatly between persons and from time to time, both in severity and swiftness of onset. For severe cases, prompt medical assistance is essential, as damage (to brain and other tissues) and even death will result from sufficiently low blood glucose levels. Converting glucose units In most countries, blood glucose is reported in terms of molarity, measured in mmol/L (or millimolar, abbreviated mM). In the
- 14. United States, and to a lesser extent elsewhere, mass concentration, measured in mg/dL, is typically used. To convert blood glucose readings between the two units: Divide a mg/dL figure by 18 (or multiply by 0.055) to get mmol/L. Multiply a mmol/L figure by 18 (or divide by 0.055) to get mg/dL. Comparative content Reference ranges for blood tests, comparing blood content of glucose (shown in darker green) with other constituents. Etymology and use of term The term 'blood sugar' has colloquial origins. In a physiological context, the term is a misnomer because it refers to glucose, yet other sugars besides glucose are always present. Food contains several different types (eg, fructose (largely from fruits/table sugar/industrial sweeteners). galactose (milk and dairy products), as well as several food additives such as sorbitol, xylose, maltose, ...). But because these other sugars are largely inert with regard to the metabolic control system (ie, that controlled by insulin secretion), since glucose is the dominant controlling signal for metabolic regulation, the term has gained currency, and is used by medical staff and lay folk alike. The table above reflects some of the more technical and closely defined terms used in the medical field. Blood glucose in birds and reptiles In birds and reptiles the processing of sugars is done differently, the pancreas is slightly more well developed in birds than in mammals, perhaps as a partial compensation for the lack of saliva and chewing. It produces carbohydrate, fat and protein digesting enzymes which are secreted into the small intestine. The liver has two distinct lobes each with its own duct leading into the small intestine. The liver, as in mammals, houses the bile, which in birds however is acidic and not alkaline as it is in mammals. Many birds do not have a gall bladder to hold the bile, and it is secreted directly into the pancreatic ducts. References 1. ^ American Diabetes Association. January 2006 Diabetes Care. "Standards of Medical Care-Table 6 and Table 7, Correlation between A1C level and Mean Plasma Glucose Levels on Multiple Testing over 2-3 months." Vol. 29 Supplement 1 Pages 51-580. John Bernard Henry, M.D.: Clinical diagnosis and Management by Laboratory Methods 20th edition, Saunders, Philadelphia, PA, 2001. Ronald A. Sacher and Richard A. McPherson: Widmann's Clinical Interpretation of Laboratory Tests 11th edition, F.A. Davis Company, 2001. See also Current research - Boronic acids in supramolecular chemistry: Saccharide recognition Blood glucose monitoring Retrieved from "http://en.wikipedia.org/wiki/Blood_sugar" Categories: Human homeostasis | Blood tests | Diabetes This page was last modified on 7 December 2009 at 16:52. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. See Terms of Use for details.
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- 16. Web Images Videos Shopping News Maps More MSN Hotmail Sign in | United States | Preferences Blood sugar Blood sugar Make Bing your decision engine Bing Normal values Reference ranges for blood tests Regulation overview outline images locations Glucose measurement ALL RESULTS REFERENCE » WIKIPEDIA ARTICLES Submit Query Sample type Search this article highlighter Reference Measurement techniques Blood sugar Blood glucose laboratory tests Clinical correlation For the song by Pendulum, see Blood Sugar / Axle Grinder. Health effects Blood sugar concentration, or glucose level, refers to Low blood sugar the amount of glucose present in the blood of a human or Converting glucose units animal. Normally, in mammals the blood glucose level is Comparative content maintained at a reference range between about 3.6 and Etymology and use of term 5.8 mM (mmol/l). It is tightly regulated as a part of Blood glucose in birds and metabolic homeostasis. reptiles Mean normal blood glucose levels in humans are about 90 References mg/dl, equivalent to 5mM (mmol/l) (since the molecular See also weight of glucose, C6H12O6, is about 180 g/mol). The total amount of glucose normally in circulating human blood is 1 therefore about 3.3 to 7g (assuming an ordinary adult ... Locations v... blood volume of 5 litres, plausible for an average adult male). Glucose levels rise after meals for an hour or two by a few grams and are usually lowest in the morning, before the first meal of the day. Transported via the bloodstream from the intestines or liver to body cells, glucose is the primary source of energy for body's cells, The fluctuation of blood sugar (red) and the sugar-lowering hormone fats and oils (ie, lipids) being primarily a compact energy insulin (blue) in humans during the course of a day with three meals. One of the effects of a sugar-rich vs a starch-rich meal is highlighted. store. Failure to maintain blood glucose in the normal range leads to conditions of persistently high (hyperglycemia) or low (hypoglycemia) Images Videos blood sugar. Diabetes mellitus, characterized by persistent hyperglycemia from any of several causes, is the most prominent disease related to failure of blood sugar regulation. Normal values view all 24 view all 15 Despite widely variable intervals between meals or the occasional consumption of meals with a substantial carbohydrate load, human blood glucose levels normally remain within a remarkably narrow range. In most humans this varies from about 80 mg/dl to perhaps 110 mg/dl (4.4 to 6.1 mmol/l) except shortly after eating when the blood glucose level rises temporarily up to maybe 140 mg/dl (7.8 mmol/l) or a bit more in non-diabetics. The American Diabetes Association recommends a post-meal glucose level less than 180 mg/dl (10 mmol/l) and a pre-meal plasma glucose of 90-130 mg/dl (5 to 7.2 mmol/l). [1] It is usually a surprise to realize how little glucose is actually maintained in the blood and body fluids. The control mechanism works on very small quantities. In a healthy adult male of 75 kg (165 lb) with a blood volume of 5 litres (1.3 gal), a blood glucose level of 100 mg/dl or 5.5 mmol/l corresponds to about 5 g (0.2 oz or 0.002 gal, 1/500 of the total) of glucose in the blood and approximately 45 g (1½ ounces) in the total body water (which obviously includes more than merely blood and will be usually about 60% of the total body weight in men). A more familiar comparison may help – 5 grams of glucose is about equivalent to a small sugar packet as provided in many restaurants with coffee or tea, with people using typically 1 to 3 packets per cup. Regulation Main article: Blood sugar regulation The homeostatic mechanism which keeps the blood value of glucose in a remarkably narrow range is composed of several interacting systems, of which hormone regulation is the most important. There are two types of mutually antagonistic metabolic hormones affecting blood glucose levels: catabolic hormones (such as glucagon, growth hormone, cortisol and catecholamines) which increase blood glucose; and one anabolic hormone (insulin), which decreases blood glucose. Glucose measurement Main article: Blood glucose monitoring Sample type Glucose can be measured in whole blood, serum (ie, plasma). Historically, blood glucose values were given in terms of whole blood, but most laboratories now measure and report the serum glucose levels. Because red blood cells (erythrocytes) have a higher concentration of protein (eg, hemoglobin) than serum, serum has a higher water content and consequently more dissolved glucose than does whole blood. To convert from whole-blood glucose, multiplication by 1.15 has been shown to generally give the serum/plasma level. Collection of blood in clot tubes for serum chemistry analysis permits the metabolism of glucose in the sample by blood cells until separated by centrifugation. Red blood cells, for instance, do not require insulin to intake glucose from the blood. Higher than normal amounts of white or red blood cell counts can lead to excessive glycolysis in the sample with substantial reduction of glucose level if the sample is not processed quickly. Ambient temperature at which the blood sample is kept prior to centrifuging and separation of plasma/serum also affects glucose levels. At refrigerator temperatures, glucose remains relatively stable for several hours in a blood sample. At room temperature (25 °C), a loss of 1 to 2% of total glucose per hour should be expected in whole blood samples. Loss of glucose under these conditions can be prevented by using Fluoride tubes (ie, gray-top) since fluoride inhibits glycolysis. However, these should only be used when blood will be transported from one hospital laboratory to another for glucose measurement. Red-top serum separator tubes also preserve glucose in samples after being centrifuged isolating the serum from cells. Particular care should be given to drawing blood samples from the arm opposite the one in which an intravenous line is inserted, to prevent contamination of the sample with intravenous fluids. Alternatively, blood can be drawn from the same arm with an IV line after the IV has been turned off for at least 5 minutes, and the arm elevated to drain infused fluids away from the vein. Inattention can lead to large errors, since as little as 10% contamination with 5% dextrose (D5W) will elevate glucose in a sample by 500 mg/dl or more. Remember that the actual concentration of glucose in blood is very low, even in the hyperglycemic. Arterial, capillary and venous blood have comparable glucose levels in a fasting individual. After meals venous levels are somewhat lower than capillary or arterial blood; a common estimate is about 10%. Measurement techniques Two major methods have been used to measure glucose. The first, still in use in some places, is a chemical method exploiting the
- 17. Blood sugar Normal values Regulation overview outline images locations Glucose measurement Sample type highlighter Measurement techniques Blood glucose laboratory tests Clinical correlation Health effects Low blood sugar Converting glucose units Comparative content Etymology and use of term Blood glucose in birds and reptiles References See also 1 Locations ... ... v... all Images Videos view all 24 view all 15
- 18. Blood sugar Normal values Regulation overview outline images locations Glucose measurement Sample type highlighter Measurement techniques Blood glucose laboratory tests Clinical correlation Health effects Low blood sugar Converting glucose units Comparative content Etymology and use of term Blood glucose in birds and reptiles References See also 1 Locations ... ... v... all Images Videos view all 24 view all 15
- 19. Blood sugar Normal values Regulation overview outline images locations Glucose measurement Sample type highlighter Measurement techniques Blood glucose laboratory tests Clinical correlation Health effects Low blood sugar Converting glucose units Comparative content Etymology and use of term Blood glucose in birds and reptiles References See also 1 Locations ... ... v... all Images Videos view all 24 view all 15
- 20. Oliguria A cardinal sign of renal and urinary tract disorders, oliguria is clinically defined as urine output of less than 400 ml/24 hours. Typically, this sign occurs abruptly and may herald serious—possibly life-threatening—hemodynamic instability. Its causes can be classified as prerenal (decreased renal blood flow), intrarenal (intrinsic renal damage), or postrenal (urinary tract obstruction); the pathophysiology differs for each classification. (See How oliguria develops, pages 442 and 443.) Oliguria associated with a prerenal or postrenal cause is usually promptly reversible with treatment, although it may lead to intrarenal damage if untreated. However, oliguria associated with an intrarenal cause is usually more persistent and may be irreversible. History and physical examination Begin by asking the patient about his usual daily voiding pattern, including frequency and amount. When did he first notice changes in this pattern and in the color, odor, or consistency of his urine? Ask about pain or burning on urination. Has the patient had a fever? Note his normal daily fluid intake. Has he recently been drinking more or less than usual? Has his intake of caffeine or alcohol changed drastically? Has he had recent episodes of diarrhea or vomiting that might cause fluid loss? Next, explore associated complaints, especially fatigue, loss of appetite, thirst, dyspnea, chest pain, or recent weight gain or loss (in dehydration). Check for a history of renal, urinary tract, or cardiovascular disorders. Note recent traumatic injury or surgery associated with significant blood loss as well as recent blood transfusions. Was the patient exposed to nephrotoxic agents, such as heavy metals, organic solvents, anesthetics, or radiographic contrast media? Next, obtain a drug history. Begin the physical examination by taking the patient's vital signs and weighing him. Assess his overall appearance for edema. Palpate both kidneys for tenderness and enlargement, and percuss for costovertebral angle (CVA) tenderness. Also, inspect the flank area for edema or erythema. Auscultate the heart and lungs for abnormal sounds and the flank area for renal artery bruits. Assess the patient for edema or signs of dehydration such as dry mucous membranes. Obtain a urine specimen and inspect it for abnormal color, odor, or sediment. Use reagent strips to test for glucose, protein, and blood. Also, use a urinometer to measure specific gravity. Medical causes Acute tubular necrosis (ATN).An early sign of ATN, oliguria may occur abruptly (in shock) or gradually (in nephrotoxicity). Usually, it persists for about 2 weeks, followed by polyuria. Related features include signs of hyperkalemia (muscle weakness and cardiac arrhythmias), uremia (anorexia, confusion, lethargy, twitching, seizures, pruritus, and Kussmaul's respirations), and heart failure (edema, jugular vein distention, crackles, and dyspnea). Calculi.Oliguria or anuria may result from calculi lodging in the kidneys, ureters, bladder outlet, or urethra. Associated signs and symptoms include urinary frequency and urgency, dysuria, and hematuria or pyuria. Usually, the patient experiences renal colic—excruciating pain that radiates from the CVA to the flank, the suprapubic region, and the external genitalia. This pain may be accompanied by nausea, vomiting, hypoactive bowel sounds, abdominal distention and, occasionally, fever and chills. Cholera. With cholera, severe water and electrolyte loss lead to oliguria, thirst, weakness, muscle cramps, decreased skin turgor, tachycardia, hypotension, and abrupt watery diarrhea and vomiting. Death may occur in hours without treatment. Glomerulonephritis (acute).Acute glomerulonephritis produces oliguria or anuria. Other features are a mild fever, fatigue, gross hematuria, proteinuria, generalized edema, elevated blood pressure, headache, nausea and vomiting, flank and abdominal pain, and signs of pulmonary congestion (dyspnea and a productive cough). Heart failure.Oliguria may occur with left-sided heart failure as a result of low cardiac output and decreased renal perfusion. Accompanying signs and symptoms include dyspnea, fatigue, weakness, peripheral edema, jugular vein distention, tachycardia, tachypnea, crackles, and a dry or productive cough. With advanced or chronic heart failure, the patient may also develop orthopnea, cyanosis, clubbing, a ventricular gallop, diastolic hypertension, cardiomegaly, and hemoptysis. Hypovolemia. Any disorder that decreases circulating fluid volume can produce oliguria. Associated findings include orthostatic hypotension, apathy, lethargy, fatigue, gross muscle weakness, anorexia, nausea, profound thirst, dizziness, sunken eyeballs, poor skin turgor, and dry mucous membranes. Pyelonephritis (acute).Accompanying the sudden onset of oliguria with acute pyelonephritis are a high fever with chills, fatigue, flank pain, CVA tenderness, weakness, nocturia, dysuria, hematuria, urinary frequency and urgency, and tenesmus. The urine may appear cloudy. Occasionally, the patient also experiences anorexia, diarrhea, and nausea and vomiting. Renal failure (chronic).Oliguria is a major sign of end-stage chronic renal failure. Associated findings reflect progressive uremia and include fatigue, weakness, irritability, uremic fetor, ecchymoses and petechiae, peripheral edema, elevated blood pressure, confusion, emotional lability, drowsiness, coarse muscle twitching, muscle cramps, peripheral neuropathies, anorexia, a metallic taste in the mouth, nausea and vomiting, constipation or diarrhea, stomatitis, pruritus, pallor, and yellow- or bronze-tinged skin. Eventually, seizures, coma, and uremic frost may develop. Renal vein occlusion (bilateral).Bilateral renal vein occlusion occasionally causes oliguria accompanied by acute low back and flank pain, CVA tenderness, fever, pallor, hematuria, enlarged and palpable kidneys, edema and, possibly, signs of uremia. Toxemia of pregnancy.With severe preeclampsia, oliguria may be accompanied by elevated blood pressure, dizziness, diplopia, blurred vision, epigastric pain, nausea and
- 21. vomiting, irritability, and a severe frontal headache. Typically, oliguria is preceded by generalized edema and sudden weight gain of more than 3 lb (1.4 kg) per week during the second trimester, or more than 1 lb (0.45 kg) per week during the third trimester. If preeclampsia progresses to eclampsia, the patient develops seizures and may slip into coma. Urethral stricture.Urethral stricture produces oliguria accompanied by chronic urethral discharge, urinary frequency and urgency, dysuria, pyuria, and a diminished urine stream. As the obstruction worsens, urine extravasation may lead to formation of urinomas and urosepsis. Other causes Diagnostic studies.Radiographic studies that use contrast media may cause nephrotoxicity and oliguria. Drugs.Oliguria may result from drugs that cause decreased renal perfusion (diuretics), nephrotoxicity (most notably, aminoglycosides and chemotherapeutic drugs), urine retention (adrenergics and anticholinergics), or urinary obstruction associated with precipitation of urinary crystals (sulfonamides and acyclovir). Nursing considerations ▪ Monitor the patient's vital signs, intake and output, and daily weight. ▪ Depending on the cause of oliguria, restrict fluids to between 0.6 and 1 L more than the patient's urine output for the previous day. ▪ Provide a diet low in sodium, potassium, and protein. ▪ Prepare the patient for diagnostic tests, such as laboratory tests (including serum blood urea nitrogen and creatinine levels, urea and creatinine clearance, urine sodium levels, and urine osmolality), abdominal X-rays, ultrasonography, a computed tomography scan, cystography, and a renal scan. ▪ Prepare the patient for dialysis. Patient teaching ▪ Explain any fluid and dietary restrictions. ▪ Explain the underlying disorder and the treatment plan. Pictures
- 22. Book Source Details Book Title: Nursing: Interpreting Signs and Symptoms Author(s): Springhouse Year of Publication: 2007 Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins. Other Book Chapters Related to Urinary symptoms Read excerpts from these other book chapters related to Urinary symptoms: Medical Books Excerpts DYSURIA "Algorithmic Diagnosis of Symptoms and Signs" (2003) ENURESIS "Algorithmic Diagnosis of Symptoms and Signs" (2003) NOCTURIA "Algorithmic Diagnosis of Symptoms and Signs" (2003) POLYURIA "Algorithmic Diagnosis of Symptoms and Signs" (2003) PROTEINURIA "Algorithmic Diagnosis of Symptoms and Signs" (2003) PYURIA "Algorithmic Diagnosis of Symptoms and Signs" (2003) DIFFICULTY URINATING "Algorithmic Diagnosis of Symptoms and Signs" (2003) FREQUENCY OF URINATION "Algorithmic Diagnosis of Symptoms and Signs" (2003) INCONTINENCE OF URINE "Algorithmic Diagnosis of Symptoms and Signs" (2003) URINE COLOR CHANGES "Algorithmic Diagnosis of Symptoms and Signs" (2003) ANURIA OR OLIGURIA "Algorithmic Diagnosis of Symptoms and Signs" (2003) Dysuria "In a Page: Signs and Symptoms" (2004) Polyuria "In a Page: Signs and Symptoms" (2004) Urinary Stream (Decreased) "In a Page: Signs and Symptoms" (2004) Dysuria "In A Page: Pediatric Signs and Symptoms" (2007) Enuresis "In A Page: Pediatric Signs and Symptoms" (2007)
- 23. More About Causes of Urinary symptoms Back to symptom: Urinary symptoms: Introduction (review 1071 causes) Next Book Extract About Urinary symptoms: Polyuria (Nursing: Interpreting Signs and Symptoms) All Book Extracts: All Online Book Extracts for Urinary symptoms More About This Book: Title: Nursing: Interpreting Signs and Symptoms Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-58255-668-7 » Next page: Polyuria (Nursing: Interpreting Signs and Symptoms) Rate This Website What do you think about the features of this website? Take our user survey and have your say: Website User Survey Medical Tools & Articles: Next articles: Polyuria (Nursing: Interpreting Signs and Symptoms) Urinary frequency (Nursing: Interpreting Signs and Symptoms) Urinary hesitancy (Nursing: Interpreting Signs and Symptoms) Urinary incontinence (Nursing: Interpreting Signs and Symptoms) Urinary urgency (Nursing: Interpreting Signs and Symptoms) Tools & Services: Bookmark this page Take a survey relating to Urinary symptoms Symptom Search Symptom Checker Medical Dictionary Give your feedback Medical Articles: Disease & Treatments Search Misdiagnosis Center Full list of interesting articles Forums & Message Boards Ask or answer a question at the Boards: I cannot get a diagnosis. Please help. Tell us your medical story. Share your misdiagnosis story. What is the best treatment for my condition? See all the Boards.
- 24. Section VI . The Kidneys And The Body Fluids This section was written following fruitful discussions with my colleagues Peter Bie, Niels-Henrik Holstein- Rathlou, Paul Leyssac, Finn Michael Karlsen, and medical students Margrethe Lynggaard and Mads Dalsgaard. The concept flux is net-transport of substance per time unit across an area unit. Flux is equal to concentration multiplied by flow or mol per time unit across a barrier area Frequently used abbreviations in this section are Chapter 24 Chapter 24. Body Fluids and Regulation Body Fluids And Regulation Study Objectives Principles Definitions Study Objectives Essentials • To define the concepts: Dehydration, hyponatraemia, intracellular fluid volume (ICV), Pathophysiology Equations extracellular fluid volume (ECV), interstitial fluid (ISF), overhydration, oxidation water, Self-Assessment radioactivity, specific activity, and total body water. Answers Highlights • To describe the daily water balance, the K+ - and Na+ -balance, sweat secretion, the Further Reading ionic composition in blood plasma, the water content of fat- and muscle- tissue and the Fig. 24-1 daily water transfer across the gastro-intestinal mucosa. To describe the osmotic pressure Fig. 24-2 Fig. 24-3 in the body fluids, the measurement of fluid compartments by indicator dilution, the Fig. 24-4 measurement of total body-K+ and -Na+ and the related dynamic pools. Fig. 24-5 Fig. 24-6 • To draw models of the body fluid compartments. Fig. 24-7 Fig. 24-8 • To explain the influence of age, sex and weight on the size of the total body water and Fig. 24-9 Fig. 24-10 its phases. To explain disorders with increased or reduced extracellular fluid volume and shock. Return to chapter 24 Return to Content • To apply and use the above concepts in problem solving and in case histories. Principles • The law of conservation of matter states that mass or energy can neither be created nor destroyed (the principle of mass balance). The principle is here used to measure physiological fluid compartments and the body content of ions. Definitions • Concentration: The concentration of a solute is the amount of solute in a given fluid volume. • Dehydration is a clinical condition with an abnormal reduction of one or more of the major fluid compartments (ie, total body water with shrinkage of blood volume or ISF). • Dextrans are polysaccharides of high molecular weight. • Intracellular fluid volume (ICV) refers to the volume of fluid inside all cells. This volume normally contains 26-28 litre (l) out of the total 42 l of water in a 70-kg person. - One litre of water equals one kg of water. • Extracellular fluid volume (ECV) refers to the interstitial and the plasma volume. The ECV contains the remaining water (14-16 kg) with most of the water in tissue fluid (ISF) and about 3 kg of water in plasma. - Interstitial fluid (ISF) is the tissue fluid between the cells in the extravascular space. • Hyperkalaemia refers to a clinical condition with plasma-[K+ ] above 5 mM (mmol/l of plasma). +
- 25. • Hypokalaemia refers to a clinical condition with plasma-[K ] below 3.5 mM. • Hypernatraemia refers to a clinical condition with plasma-[Na+ ] above 145 mM. • Hyponatraemia refers to a clinical condition with plasma-[Na+ ] below 135 mM. • Oedema refers to a clinical condition with an abnormal accumulation of tissue fluid or interstitial fluid. • Osmolality is a measure of the osmotic active particles in one kg of water. Plasma- osmolality is given in Osmol per kg of water. Water occupies 93-94% of plasma in healthy persons. Plasma osmolality is normally maintained constant by the antidiuretic hormone feedback system. • Overhydration refers to a clinical condition with an abnormal increase in total body water resulting in an increased ECV and thus salt accumulation. • Oxidation water or metabolic water (oxidative phosphorylation) refers to the daily water production by combustion of food - normally 300-400 g of water daily in an adult. • Radioactivity is measured as the number of radioactive disintegrations per s (in Becquerel or Bq per l). One disintegration per s equals one Bq. • Total body water is destributed between two compartments separated by the cell membrane: The intracellular and the extracellular fluid. Essentials This paragraph deals with 1. The three major fluid compartments, 2. Water balance, 3. Body potassium, 4. Body sodium, 5. The indicator dilution principle, 6. The renin- angiotensin-aldosterone cascade, 7. Output contol, 8. Regulation of renal water excretion, and 9. Regulation of renal sodium excretion. Read first about the nephron (paragraph 1 of Chapter 25). 1. The three major fluid compartments The three major body fluid compartments are the intracellular fluid volume (ICV), the interstitial fluid volume (ISV) and the vascular space (Chapter 1, Fig.1-4). Water permeable membranes separate the three compartments, so that they contain almost the same number of osmotically active particles per kg. The three compartments have the same concentration expressed as mOsmol per kg of water or the same freeze-point depression. They are said to be isosmolal, because they have the same osmolality. The so-called lean body mass, which means a body stripped of fat, contains 0.69 parts of water (69%) of the total body weight in all persons. - Such high values are observed in the newborn and in extremely fit athletes with minimal body fat. Babies have a tenfold higher water turnover per kg of body weight than adults do. As an average females have a low body water percentage compared to males. Such differences show sex dependency, but the important factor is the relative content of body fat, since fat tissue contains significantly less water (only 10%) than muscle and other tissues (70%). This is why the relative water content depends upon the relative fat content. The average for most healthy persons is 60% of the body weight. Sedentary, overweight persons contain only 50-55 % water dependent on the body fat content. The relative content of body fat rises with increasing age and body weight, and the relative mass of muscle tissue becomes less. Consequently, the body water fraction falls with increasing body weight and age. Aging implies loss of cells, but the ECV is remarkably
- 26. constant through life and under disease conditions. Each body (weight 70 kg) contains 4 mol of both sodium and potassium (ie, the total ion pool). A minor fraction of the potassium is radioactive. The calcium and magnesium content is 25 and 1 mol, respectively. In the renal tubule cells the epithelium is a single layer of cells, joined by junctional complexes near their luminal border (Fig. 25-7). Solutes can traverse the epithelium through transcellular or paracellular pathways. Virtually every cell membrane in the body contains the Na+ - K+ -pump, which maintains the low intracellular Na+ -concentration and develops the negative, intracellular voltage. In the renal tubule cells the Na+ - K+ -pump, is located in the basolateral membrane. Read more about the nephron in Chapter 25 and about hormonal control later in paragraph 8 and 11 of this Chapter. Unfortunately, the simple laws of dilute solutions are unprecise at physiological concentrations. Rough estimates are based on the assumptions that extracellular sodium is associated with monovalent anions and that deviations in osmolality are twice the deviation in plasma sodium concentration. ICV: The dominating intracellular solute is potassium (K+ ), balanced by phosphate and anionic protein, whilst the dominating extracellular solute is NaCl. All compartments have almost the same osmolality 300 mOsmol* kg-1 of water. The thin cell membrane - or the endothelial barrier between ISF and plasma in the vascular phase - cannot carry any important hydrostatic gradient. Water passes freely between the extra- and intra-cellular compartment, as osmotic forces govern its distribution and the membranes are water permeable. Fig. 24-1: The daily water transfer across the gastrointestinal barrier in a healthy standard person. The ICV comprises 26-28 kg out of the total 42-kg of water in a 70-kg person (Fig. 1-4). ECV: The ECV compartment comprises the remaining water (14-16 kg) with most of the water in tissue fluid (interstitial fluid or ISF) and 3 kg of water in plasma (Chapter 1, Fig. 1-4). The size of the ECV compartment is proportional to the total body Na+ . Changes in plasma osmolality indicate problems in water balance. A [Na+ ] in ECV of 150 mmol per kg of plasma water corresponds to a total osmolality of 300 mOsmol per kg. Alterations in plasma-[Na+ ] (osmolality) will be followed by similar changes of the ECV osmolality, because the permeability of of the capillary barrier for Na+ and water is almost equal. The daily water transfer across the gastrointestinal tract amounts to approximately 9 l in each direction (Fig. 24-1). 2. Water balance A healthy person on a mixed diet in a temperate climate receives 1000 ml with the food and drinks 1200 ml daily. Balance is maintained as long as the water loss is the same (Fig. 24-2). Fig. 24-2: The daily water balance in a 70-kg healthy person on a mixed diet. The apparent imbalance between input (2200 ml) and output (2500 ml) is covered by 300 ml of metabolic water. Water is lost in the urine (1500 ml), in the stools (100 ml), in sweat and evaporation from the respiratory tract (900 ml) as a typical example. The total loss of water is 2500 ml, and this corresponds perfectly to the intake plus a normal production of 300 ml of metabolic water per 24 hours (Fig. 24-2).
- 27. 3. Body potassium The daily dietary intake of potassium varies with the amount of fruit and vegetables consumed (75-150 mmol K+ daily). More than 90% of the body potassium is located intracellularly. Only a few percent of the K+ in the body pool are found outside the cells and subject to control (Fig. 24-3). The main renal K+ -reabsorption is passive and paracellular through tight junctions of the proximal tubules. Moreover K+ -excretion can vary over a wide range from almost complete reabsorption of filtered K+ to urinary excretion rates in excess of filtered load (ie, net secretion of K+ ). The Na+ -K+ -pump located in the cell membrane, maintains the high intracellular [K+ ] and the low intracellular [Na+ ]. The energy of the terminal phosphate bond of ATP is used to actively extrude Na+ and pump K+ into the cell. The membrane also contains many K+ - and Cl - -channels, through which the two ions leak out of the cell. In myocardial cells, as in skeletal muscle and nerve cells, K+ plays a major role in determining the resting membrane potential (RMP), and K+ is important for optimal operation of enzymatic processes. Under normal conditions, the RMP of the myocardial cell is determined by the dynamic balance between the membrane conductance to K+ and to Na+ . As [K+ ] out is reduced during hypokalaemia, the membrane depolarises causing voltage-dependent inactivation of K+ -channels and activation of Na+ -channels, allowing Na+ to make a proportionally larger contribution to the RMP. Fig. 24-3: The total body K + -pool in a healthy person comprises 4000 mmol with more than 90% intracellularly. The normal ECG and the ECG of a patient with hyperkalaemia is shown to the right. The K+ -permeability is around 50 times larger than the Na+ -permeability, so the RMP of normal myocardial cells (typically: -90 mV) almost equals the equilibrium potential for K + (-94 mV). The excretion of K+ by overload is almost entirely determined by the extent of distal tubular secretion in the principal cells. Any rise in serum [K+ ] immediately results in a marked rise in K+ -secretion. This transport mechanism is controlled by aldosterone and by K+ . Aldosterone stimulates the secretion of K+ and H+ by the principal cells of the renal distal tubules and collecting ducts (Fig. 25-11). This is why chronic acidosis decreases and chronic alkalosis increases K+ -secretion. – Actually, acute acidosis may reduce K+ - secretion. Of the consumed K+ , 75-150 mmol is daily absorbed in the intestine. Since 90% is excreted renally in a healthy person, there must be a minimum in a typical volume of 1500 ml of daily urine with a concentration of (75/1.5) = 50 mM. Normal urinary [K+ ] is at least 30 mM. A high urinary [K+ ] is indicative of a high total body K+ or a high intake of K+ . The normal excretion fraction (Chapter 25) for K+ is 0.10 (10% or 90 mmol of the 900 mmol in the daily filtrate) corresponding to the daily intake (Fig. 24-4). A K+ -poor diet leads to hypokalaemia with less than 20 mmol K+ in the daily urine. A K+ -rich diet triggers a large secretion and a high excretion in the urine (Box 25-1). A low urinary [K+ ]
- 28. is indicative of a low total body K+ or of extracellular acidosis with transfer of K + from the cells in exchange of H+ . A low [K+ ] in the distal tubule cells reduces the K+ -excretion. The normal plasma-[K+] level is dependent upon the exchange with the cells, the renal excretion rate, and the extrarenal losses through the gastrointestinal tract or through sweat. Measurement of total and exchangeable body potassium Our natural body potassium is 39K, but we also contain traces of naturally occurring radioactivity (0.00012 or 0.012% is 40K with a half-life of 1.3×109 years). When using this natural tracer, injection of radioactive tracer is avoided. The person to be examined is placed in a sensitive whole body counter, and the total activity of the tracer 40K in the body (S Bq) is measured. Specific activity (SA) is the concentration of radioactive tracer in a fluid volume divided by the concentration of naturally occurring, non-radioactive mother-substance. The concentration of mother-substance is traditionally measured in mmol per l (mM). SA is equal to radioactivity (A) per non-radioactive mass unit, m (ie, A/m in Bq/mol). Following even distribution, the SA for a certain substance must be the same all over the body. SA is preferably measured in plasma (with scintillation counters or similar equipment). Specific activity (SA) is here the number of Bq 40K per mol of mother substance ( 39K) in the whole body. We can calculate all 39K or total body potassium: S/SA mol per whole body - when SA is known to be 0.012% or a fraction of 0.00012. The total body potassium of a healthy person is 4000 mmol. The SA of 40K implies a 40K/39K ratio of 0.48 mmol/4000 mmol (=0.00012). An exchangeable ion pool in our body is the dynamic part of the total specific ion content. The remaining content is fixed as insoluble salts in the bones. The dynamic character implies the use of a dilution principle to measure such a pool. In order to measure the exchangeable body potassium pool, a radioactive tracer is injected, such as 42K with a physical half-life of 12 hours (12.4 hours) and urine is collected. The first urine sample is from the first 12 hours, and the second sample is covering 12 - 24 hours. The total tracer dose given must be adjusted for by the loss of tracer in the urine and by the radioactive decay during the first 12 hours mixing period. The two urine samples obtained are examined for tracer and for natural potassium. The tracer is assumed to distribute just as natural potassium after 12 - 24 hours. When the tracer is distributed evenly in the exchangeable body potassium, its SA must be the same in urine, plasma or elsewhere in the body. The exchangeable body potassium is calculated by Eq. 24-2 . The specific activity for the tracer (SA Bq per mol) is known from the plasma measurements. In this way we measure the exchangeable body potassium. The normal values are 41 mmol 39K per kg body weight for females, and 46 mmol per kg for males. 4. Body sodium ( 23Na) The exchangeable body sodium is easy to measure using the dilution principle and a minimum of equipment. Our natural non-radioactive body sodium is 23Na. We administer the radioactive tracer, 24Na, with a physical half-life of 15 hours. We have to use a total period of 30 hours to secure even distribution in the ECV. The total tracer dose given, must be adjusted for by the loss of tracer in the urine, and the radioactive decay of 24Na (see the decay law in Chapter 1). The exchangeable body sodium is calculated by Eq. 24-2. We know the specific activity for the tracer (SA Bq/mol) from the plasma measurements; 23
- 29. therefore calculation of the exchangeable body Na is easy. The normal value for exchangeable body sodium is 40 mmol/kg of body weight. In a patient with a body weight of 75 kg the exchangeable sodium is (75 × 40) = 3000 mmol. The non-exchangeable sodium is fixed in the bones. The total body sodium is measured following discrete radiation with a method called neutron activation analysis. The whole body of the patient is exposed to radiation with neutrons. A small fraction of the natural 23Na now becomes radioactive sodium ( 24Na) by uptake of an extra neutron. A sensitive whole body counter records the radiation from 24Na. Now we can calculate the total body sodium. Normally, the total body sodium is 1000 mmol larger than the exchangeable sodium due to the fixed sodium content of the bones (1000 + 3000 mmol = 4000 mmol 23Na). Fig. 24-4: Body fluid electrolytes. Water permeable membranes separate the three compartments, which contain almost the same number of osmotically active particles per kg. The sum columns of electrolyte equivalents in muscle cells are essentially higher than the extracellular sum columns of equivalents, because cells contain proteins, Ca2+, Mg 2+ and other molecules with several charges per particle (Fig. 24-4). The above columns show the ionic composition per kg of water, so we have 150 mmol of Na per kg of plasma water. Normally, one litre of plasma has a weight of 1.040 kg and contains 10% of dry material. Consequently, one litre of plasma contains 0.940 l of water, and the rest consists of plasma proteins and small ions. Thus the fraction of water in plasma (F water) is typically 0.94. 5. The indicator dilution principle Mass conservation is always the underlying principle. The amount of indicator n mol distributes in V litres of distribution volume. We measure the concentration Cp in mM, following even distribution, and calculate V: V = n/C p . Errors: Uneven distribution of indicator introduces a systematic error. - A non- representative concentration of indicator in the plasma makes it insufficient to correct for plasma proteins alone. - Loss of indicator to other compartments is inevitable. - Elimination or synthesis of indicator in the body occurs as frequent errors. - The indicator may be toxic or in other ways change the size of the compartment to be measured. Total body water, ECV, plasma volume, and the elimination rate constant are measured as follows: 5 a. Total body water Total water is measured by the help of the dilution principle. Tritium marked water is a good tracer. The equilibrium period is 3-6 hours. n mol of indicator divided by Cp mmol of indicator per l is equal to the distribution volume (V) for the indicator. Healthy adolescents and children have normal values around 60% of the body weight assuming one l of water to be equal to one kg. Adult males and females with a sedentary life style and larger fat fractions contain only 50% of water. 5 b. The extracellular fluid volume (ECV) is measured by administration of a priming dose of inulin intravenously. Then inulin is infused to maintain a steady state with constancy of the plasma concentration of inulin (Cp ).
- 30. The patient then urinates, and the infusion is stopped with collection of a plasma sample. For the next 10 hours the patient collects his urine, which makes it possible to measure all the body inulin present at the end of the infusion (n mol) assuming all inulin excreted. Dividing n with Cp gives the volume of distribution (V) after correcting for the difference in protein concentration between plasma and ISF (Eq. 24-1). Chromium-ethylene-diamine-tetra-acetate ( 51Cr-EDTA) is a chelate with a structure that cannot enter into cells. The chelate molecule contains radioactive Cr, making it easy to measure. The 51Cr-EDTA distributes and eliminates itself in the extracellular fluid volume (ECV) just as inulin and is therefore used to measure ECV. – For clearance measurements, we inject a single dose intravenously, and draw blood samples every hour for 5 hours. The clearance of 51Cr-EDTA is independent of Cp and a good estimate of GFR just like the inulin clearance. Since the indicator is cleared from the ECV only, it is possible to measure its size. Such methods - including renal lithium reabsorption - are important during renal function studies. Normal values for ECV are approximately 20% of the body weight or 14- 17 kg. Chronically ill patients with debilitating diseases often maintain their ECV remarkably well in spite of marked reductions in the cell mass of their body. 5 c. The plasma volume Also here, the dilution principle is used. The indicator for plasma volume can be Evans Blue (T 1824) that binds to circulating plasma albumin. A small dose of albumin, marked with radioactive iodine, is also a good indicator (iodine 131 has a physical half-life of 8 days). The indicator concentration in plasma (Cp ) is measured every 10-min for an hour after the administration, and the log of Cp is plotted with time. Extrapolation to the time zero determines the maximum concentration of indicator in plasma. This corrects for the biological loss, while the indicator distributes itself in the plasma phase. The tracer dose divided by Cp at time zero provides us with the intravascular plasma volume. Normal values for the plasma volume are close to 5% of the body weight. In diabetics and hypertensive patients the tracer is lost more readily through their leaky capillaries to the interstitial fluid than in healthy persons (increased transcapillary escape). 6. The renin-angiotensin-aldosterone cascade Macula densa is described in paragraph 9 of Chapter 25. The most likely intrarenal trigger of the renin-angiotensin-aldosterone cascade is the falling NaCl concentration of the reduced fluid flow at the macula densa in the distal renal tubules (Fig. 24-5). The NaCl concentration at the macula densa falls, when we lose extracellular fluid, move into the upright position and when the blood pressure falls. Renin is a proteinase that separates the decapeptide, angiotensin I, from the liver globulin, angiotensinogen. When angiotensin I passes the lungs or the kidneys, a dipeptide is separated from the decapeptide by angiotensin converting enzyme (ACE). This process produces the octapeptide, angiotensin II. Angiotensin II has multiple actions that minimize renal fluid and sodium losses and maintain arterial blood pressure. 1. Angiotensin II stimulates the aldosterone secretion by the adrenal cortex, and through this hormone it stimulates Na+ -reabsorption and K+ -(H+ )-secretion in the
- 31. distal tubules (Fig. 24-5). - Angiotensin II is in itself a potent stimulator of tubular Na+ -reabsorption. 2. Angiotensin II inhibits further renin release by negative feedback. 3. Angiotensin II constricts arterioles all over the body including a strong constriction of the efferent and to some extent also the afferent arteriole. Hereby, the renal bloodflow (RBF) and to a lesser extent the glomerular filtration rate (GFR) is reduced. 4. Angiotensin II inhibits the absolute proximal tubular reabsorption – contributing to the reduction of GFR. 5. Angiotensin II enhances sympathetic nervous activity. Fig. 24-5: The renin-angiotensin-aldosterone cascade. Sympathetic stimulation of the renal nerves stimulates renin secretion directly via b- adrenergic receptors on the JG cells just as falling blood pressure in the preglomerular arterioles. - b-blocking drugs and angiotensin II inhibit the renin secretion (Fig 24-5). The combined effects from the whole renin cascade is extracellular fluid homeostasis. In contrast, exposure to stress and painful stimuli triggers the combined sympatho- adrenergic system with release of catecholamines, gluco- and mineralo-corticoids, and ACTH from the hypophysis. ACTH stimulates further the secretion of the glucocorticoid, cortisol, from the adrenal cortex. 7. Output control The body uses output control, when it is overloaded with water or with sodium. The most important osmotically active solute in ECV is NaCl, because it only passes into cells in small amounts. Urea, glucose and other molecules with modest concentration gradients are without importance, because they distribute almost evenly in the fluid compartments. Healthy persons use two primary control systems: 1) The osmolality (osmol per kg of water) or ion concentration controls our elimination of water. 2) The change of blood volume (ECV) or pressure controls sodium excretion - not osmolality. Only when the arterial blood pressure falls drastically the body will drop its protection of normal concentration. In such a disease state large amounts of ADH molecules are released in an attempt to improve the volume and blood pressure. 8. Regulation of renal water excretion The primary control of the renal water excretion is osmolality control (Fig. 24-6). Since 2/3 of the body water normally is located within the cells, this is also an intracellular volume control. Following water deprivation even an increase in plasma osmolality of only one per cent stimulates both the hypothalamic osmoreceptors and similar (angiotensin-II-sensitive) thirst receptors. Thirst may increase the water intake of the individual and thus increase the ECV, with negative feedback to the thirst receptors. Activation of the hypothalamic osmoreceptors and thirst receptors increases the hypothalamic neurosecretion to the neurohypophysis and releases antidiuretic hormone (ADH or vasopressin). Hyperosmolality elicits a linear increase in plasma ADH, which causes water retention (Fig. 24-6) until isosmolality is reached. ADH increases the reabsorption of water from the fluid in the renal cortical and medullary collecting ducts. ADH binds to receptors on the basolateral surface of the tubule cells,
- 32. where they liberate and accumulate cAMP. This messenger passes through intermediary steps across the cell to the luminal membrane, where the number of water channels (aquaporin 2) are increased. The luminal cell membrane is thus rendered water-permeable, which increases the renal water retention. The increased water reabsorption leads to a small, concentrated urine volume (antidiuresis), and a net gain of water that returns ECF osmolality towards normal. Initially, osmolality control overrides blood volume control. Fig. 24-6: Primary osmolality control of the renal water excretion. ADH and thirst systems maintain osmolality and ICV within narrow limits. Water overload decreases ECF osmolality and has the reverse effect, because the hypothalamic osmoreceptors suppress the ADH release, and the renal water excretion is increased already after 30 min (Fig. 24-6). When a person rapidly drinks one litre of water, the intestine absorbs water. Ions diffuse into the intestinal lumen and the blood osmolality falls causing a block of the ADH secretion (Fig. 24-6). Pure water is distributed evenly in all three body fluid compartments – just like intravenous infusion of one litre of 5% glucose in water. Intake of one l of isotonic saline implies ECV expansion, without dilution of body fluids. This expansion will not increase the urine volume much, so the increased ECV can be sustained for many hours. An intravenous infusion of one l of large dextran molecules (macrodex) stays mainly in the vascular space. 9. Regulation of renal sodium excretion In healthy persons, changes of blood volume (or ECV) or blood pressure control sodium excretion (Fig. 24-7). The dominating cation of the ECV is Na+ . The sodium intake is balanced by the sodium excretion as long as the thirst and other homeostatic systems are functional. During conditions where sodium intake exceeds renal sodium excretion, total body sodium and ECV increase. Conversely, total body sodium and ECV decrease, when sodium intake is lower than renal sodium excretion. This is because volume-pressor-receptors detect the size of the circulating blood volume (ECV) or pressure, and effector mechanisms adjust the renal sodium excretion accordingly. The volume-pressor-receptors are widely distributed. Low-pressure receptors are found in the pulmonary vessels and in the atria. An increased blood volume can also increase the arterial blood pressure and stimulate the well-known high-pressure baroreceptors in the carotid sinus and the aortic arch. Increased arterial pressure reduces sympathetic tone – also in the kidneys, whereas decreasing arterial pressure enhances sympathetic tone and renal salt retention. Arterial pressure receptors are also located in the renal preglomerular arterioles. Both stimuli in Fig. 24-7 release renin from macula densa, whereby angiotensin II and aldosterone is secreted (both sodium retaining hormones). A decrease in circulating blood volume leads to a decrease in NaCl delivery to the macula densa and release of the renin cascade. Conversely, an increase in circulating blood volume with increased NaCl delivery to the macula densa suppresses renin release and increases sodium excretion (Fig. 24-7). Fig. 24-7: Primary blood volume-pressure control of the renal Na+ -excretion. The effective circulating blood volume is protected – also during shock (Na+ -retention) and during hypertension (natriuresis). Increased salt intake increases blood volume and leads to natriuresis, possibly augmented by release of ANP (see below), nitric oxide and other factors. The excretion of Na+
- 33. depends upon several effector mechanisms out of which three are classical: The first factor is the glomerular filtration rate (GFR), which is responsible for the size of the filtered flux of Na+ across the glomerular barrier in the kidneys. Renal prostaglandins, generated in response to angiotensin II, are involved in maintaining the filtered flux of Na+ . The second factor is the renin-angiotensin-aldosterone cascade (Fig. 24-5). The third factor consists of peptides with natriuretic effects. The most well-known peptide is called atrial natriuretic peptide (ANP) and originates from granules of the atrial myocytes. A low circulating blood volume with low atrial pressure increases renal sympathetic tone, reduces the stimulus of the low-pressure receptors in the atrial wall and thus the ANP secretion. Hereby, the natriuresis is reduced. - Renal natriuretic peptide or urodilatin from the distal tubule cells is related to ANP. Urodilatin has been isolated from human urine and contains four amino acids more than ANP. An increase in effective circulating blood volume, increases atrial pressure, reduces sympathetic tone and releases ANP and urodilatin leading to increased natriuresis. The main purpose of these mechanisms is to maintain an effective circulating blood volume by an increase or a decrease of the renal excretion of Na+ . Initially, osmolality control is dominating. Finally, after a dangerous reduction in blood volume, volume-pressure receptors override the hypothalamic osmoreceptors and stimulate the ADH release and thirst. In the terminal phase, the body protects effective circulating blood volume at the expense of ECF osmolality. Pathophysiology This paragraph deals with 1. Dehydration, 2. Overhydration, 3. Hyponatraemia, 4. Hypernatraemia, 5. Hypokalaemia, and 6. Hyperkalaemia. 1. Dehydration Dehydration is an abnormal reduction of the major fluid volumes (total body water with shrinkage of ECV). When we lose more than 5% of the total body water it has clinical consequences. The condition is life threatening if the patient loses 20 %. Accidents and surgery with a period of water deprivation, imply a rise in ECF osmolality and thus stimulation of both thirst and the hypothalamic osmoreceptors, whereby ADH is released. - Symptoms and signs of dehydration are thirst, dry mucous membranes, and decreased skin elasticity or turgor due to loss of ISF. Loss of effective circulating blood volume implies a low blood pressure in both the venous and the arterial system. Loss of more than one litre of ECV causes postural hypotension with dizziness, confusion and cerebral failure. Empty veins and cold skin characterise the peripheral venoconstriction. Finally, there is extreme tachycardia, which turns into terminal bradycardia and an arterial blood pressure that approach zero. Loss of salt and water frequently develops into hypo-osmolal dehydration (Fig. 24-8). This is because the thirst forces the patient to drink (salt free) water. Water dragged into the cells further reduces the hyposmolal ECV (Fig. 24-8). The small ECV elicits a hyperaldosteronism, which is called secondary, because it is not initiated as primary hypercorticism in the adrenal cortex. A precise compensation of the water loss results in pure hyponatraemia, where water eventually is drawn from ECV into the cells. The low [Na+ ] around the swelling cells reduces the potential gradient across the cell membranes with increased neuromuscular irritability (muscular twitching) and cardiac arrhythmias. Isosmolal dehydration is a proportional loss of water and solutes. There is no concentration
- 34. gradient over the cell membranes, and the loss is mainly from ECV (Fig. 24-8). Fig. 24-8: Dehydration (hyperosmolal, isosmolal and hyposmolal). Hyperosmolal dehydration occurs in persons deprived of water. The hyperosmolal ECV drags water from ICV and dehydrates the cells (Fig. 24-8). This is intracellular dehydration. The hyperosmolality liberates ADH to restrict the water loss. The patient excretes a very small urine volume. Persons deprived of water at sea may drink seawater. Sea water is hypertonic saline and the victims die faster. When hypertonic saline reaches the ECV it aggravates the intracellular dehydration simultaneously with an extracellular overhydration. Intracellular dehydration leads to respiratory arrest and death of thirst. 2. Overhydration Overhydration is an abnormal increase of total body water - in particular ECV, and thus salt accumulation. The increase in the interstitial fluid volume is called oedema. Overhydration frequently occurs among patients in fluid therapy (ie, overhydration of iatrogenous origin). Increased salt intake by mouth is compensated by increased salt excretion by normal kidneys. However, a large saline infusion (0.9% NaCl) will expand ECV and total body water (isosmolal overhydration in Fig. 24-9). Inappropriately large infusions of saline lead to iatrogenous hyperosmolal overhydration, if they lose more water than salt (Fig. 24-9). Hyperosmolality drags water from the cells, so that the patient develops intracellular dehydration with hallucinations, loss of consciousness and eventually respiratory arrest. The patient with hyposmolal overhydration is typically in fluid treatment and develops muscle cramps and disorientation. The skin turgor is normal. A low serum - [Na+ ] confirms the diagnosis. The water overload in ECV is dragged into the cells in hyposmolal overhydration until osmolality balance (Fig. 24-9). In the brain and the muscles this intracellular overhydration causes headache, disorientation, increased spinal pressure, coma and muscle cramps. Both hyposmolal and hyperosmolal intracellular overhydration conditions are characterised by cerebral symptoms and signs. Fig. 24-9: Overhydration (hyperosmolal, isosmolal, and hyposmolal). Acute renal failure with decreased GFR reduces the flux of filtered NaCl (first factor) and thus the Na+ -excretion. Oedema is a clinical condition where the interstitial fluid volume (ISF) is abnormally large. A voluminous ISF is usually due to increased hydrostatic venous pressure (heart insufficiency), or a reduced colloid osmotic pressure (hypoproteinaemia) as predicted from Starlings law for transcapillary transport. Reduced protein synthesis (liver disease) and abnormal protein loss with the urine (proteinuria) causes hypoproteinaemia. Thus protein-losing kidneys are involved. Capillary damage (allergy, burns, inflammation etc) with increased capillary permeability causes local oedema. – Obstruction to lymphatic drainage can also cause oedema (scarring after radiation therapy, elephantiasis etc). Cardiac insufficiency with increased venous pressure and oedema formation increases
- 35. sympathetic tone and thus releases the renin-angiotensin-aldosterone cascade (Fig. 24-5) causing Na+ -retention. Hepatic cirrhosis activates the cascade in a similar way - possibly including the release of nitric oxide. Hypoalbuminaemia reduces the colloid osmotic pressure of plasma, whereby water is distributed from the vascular space to the ISF. The fall in effective circulatory volume activates the renin cascade and leads to Na+ -retention. NSAIDs can activate the renin-angiotensin-aldosterone cascade, and the increased aldosterone leads to Na+ -retention and overhydration. Angiotensin II-receptor antagonists and ACE-inhibitors are utilized clinically to block the effects of angiotensin II in congestive heart failure, diabetes mellitus and hypertension. Blockade of the cascade reduces both preglomerular and postglomerular resistances. The supine position at bed rest increases venous return. This implies an increased cardiac output (Starlings law), a reduced ANF secretion from the atrial walls and a reduced renin- angiotensin-aldosterone cascade. This is why bed rest is beneficial for disorders with salt accumulation. 3. Hyponatraemia Hyponatraemia (ie, plasma-[Na+ ] below 135 mM) is associated with dehydration, overhydration or normohydration (ie, a normal ECV and total body sodium content). Hyponatraemia with reduced ECV (ie, salt-deficient hyponatraemia) is caused by a salt loss in excess of the high water loss (ie, hyposmolal dehydration in Fig 24-10). This is seen in any type of hypoadrenalism including the rare primary hypoadrenalism (Addison’s disease). In Addison’s disease the entire adrenal cortex is destroyed by autoimmune reactions (80%) or by malignancy or infection. All three types of hormones are insufficiently produced (mineralocorticoids, glucocorticoids and sex hormones). The lack of aldosterone leads to Na+ -excretion and K+ -retention with hyponatraemia combined with hyperkalaemia resulting in dehydration and hypotension. Hyponatraemia is developed in the following way (Fig. 24-10): 1. The first step is the salt loss in excess of the water loss. 2. Since the ECF-[Na+ ] is low, the ADH secretion is suppressed, and the water excretion is increased. Hereby, both the ISF and the vascular spaces are reduced often by more than 10%. 3. This is an adequate stimulus for the volume-pressure receptors, which override the osmoreceptors, whenever the effective circulatory volume is threatened. Fig. 24-10: The three body fluid compartments in a patient with salt-deficient hyponatraemia. The volume-pressure receptors stimulate both thirst and the release of ADH. The effective circulating volume is protected at the expense of osmolality! Still the blood pressure is falling, which impairs cerebral perfusion, causing confusion, headache and coma. The hyponatraemia implies a reduced resting membrane potential and thus a low threshold for neuromuscular stimulation resulting in muscle cramps. The large renal loss is seen with osmotic diuresis (hyperglycaemia and uraemia), excessive
- 36. use of diuretics, renal tubular reabsorption defects, adreno-cortical insufficiency as aldosterone-antagonist-intoxication or other types of hypoaldosteronism. The extra-renal loss is often large from excessive sweating, diarrhoea, haemorrhage, vomiting, loss with ascites or bronchial secretion, and transudation from cutaneous defects. Normal kidneys normally compensate extra-renal loss. The urinary excretion of salt and water falls in response to volume depletion, so the urine is concentrated - but with less than 10 mM Na+ . Normal sweat is a hypotonic solution, because Na+ is reabsorbed in the duct system. The [Na+ ] can increase up to 80 mM with increasing sweat flow - due to the limited time for the aldosterone-controlled Na+ -reabsorption. Increased salt intake by mouth or intravenously is required as a supplement to the treatment directed at the primary cause. Low plasma- [Na+ ] in a chronically salt-deficient patient suggests a high aldosterone secretion from the adrenal zona glomerulosa. Further administration of aldosterone therefore may not have any effect. Hyponatraemia with increased ECV (water-excess hyponatraemia) is often caused by cardiac, hepatic, and renal insufficiency or by hypoalbuminaemia - see hyposmolal overhydration (Fig. 24-9). Hyponatraemia with normal ECV is often caused by stress (surgery, psychogenic polydipsia), abnormally high ADH release (in the syndrome of inappropriate antidiuretic hormone secretion, and in vagal neuropathy), increased sensitivity to ADH by drugs such as chlorpropamide and tolbutamide, or by intake of ADH-like substances (oxytocin). Pseudo-hyponatraemia is characterised by a spuriously low plasma value measured conventionally in the total volume of plasma, which includes an extra volume in cases with hyperlipidaemia or hyperproteinaemia etc. Plasma osmolality or plasma-Na+ measured with ion selective electrodes is the choise and the direct read value is normal. This is because Na+ is confined to the aqueous phase. Treatment of artefactual hyponatraemia (taking blood from an extremity into which isotonic glucose is infused) is also unnecessary. 4. Hypernatraemia The normal plasma-[Na+ ] is 135-145 mM, and values above 170 mM are rare. Excessive infusion of saline (0.9% NaCl or 154 mM) can lead to hypernatraemia. Such alarmingly high levels create an emergency situation, where glucose infusion is indicated initially in order to reduce the high level slowly. The increased plasma osmolality elicits a strong desire to drink. The cause is sometimes water deficit due to pituitary diabetes insipidus, or to nephrogenic diabetes insipidus, where ingestion of nephrotoxic drugs have made the renal collecting ducts resistant to ADH. – Osmotic diuresis also causes water deficit with hypernatraemia just as excessive loss of water through the skin or lungs. Primary hyperaldosteronism (Conns disease) and all types of secondary hyperaldosteronism also lead to hypernatraemia combined with hypokalaemia and enlarged blood volume. Cerebral failure and convulsions are alarming signs, but there are no specific symptoms and signs of hypernatraemia.
- 37. Polyuria, polydipsia and thirst suggest diabetes. Diabetes mellitus is easy to diagnose, and diabetes insipidus shows a low urinary osmolality. Pituitary diabetes insipidus is treated with an analogue of ADH (desmopressin, with a low pressor-effect). 5. Hypokalaemia The normal potassium ion concentration in blood plasma is 3.5-5 mM. Hypokalaemia is caused by renal or extra-renal K+ -loss or by restricted intake. Long standing use of diuretics without KCl compensation is a frequent cause of hypokalaemia. Hyperaldosteronism (increased aldosterone secretion) is another cause. Vomit fluid only contains 5-10 mM of K+ . Still, prolonged vomiting develops into hypokalaemia, because the Na+ -loss stimulates the aldosterone secretion, which increases K + -excretion in the kidneys. Profuse diarrhoea causes marked hypokalaemia, also because the diarrhoea fluid contains up to 50 mM of K + . Hypokalaemia is seen in cardiac patients receiving digoxin treatment. Digoxin toxicity is imminent, because digoxin firmly binds to myocardial cells in hypokalaemia. Treatment must be directed towards the underlying cause. Infusion of potassium -rich fluid is dangerous, because of the marginal distance to hyperkalaemia. The reduced extracellular K+ hyperpolarises the cell membrane (increases the negativity of the voltage across the membrane). This reduces the excitability of neurons and muscle cells. Thus, hypokalaemia can result in muscle weakness and paresis. Hypokalaemia is associated with an increased frequency of cardiac arrhythmias with atrial and ventricular ectopic beats in particular in patients with cardiac disease . - Hypokalaemia inhibits release of adrenaline, aldosterone and insulin. 6. Hyperkalaemia Acute hyperkalaemia (ie, plasma-[K+ ] above 5 mM) is a normal condition following severe exercise, and normal kidneys easily eliminate K+ . In disease states the causes are insufficient renal excretion or increased release from damaged body cells as during long lasting hunger, exercise or in severe burns. A plasma- [K+ ] above 7 mM is life threatening due to asystolic cardiac arrest. Long term intake of b-blocking drugs, which inhibit the Na+ -K+ -pump, leads to hyperkalaemia that is accentuated by exercise. Hyperkalaemia reduces the size of the resting membrane potential (reduces the negativity of the voltage), whereby the threshold for firing is approached in neurons and striated muscle cells. The increased excitability in hyperkalaemia results in muscle contractions, cramps followed by muscle weakness. Hyperkalaemia leads to decreased cardiac excitability, hypotension, bradycardia and eventual asystole. The ECG is characterised by increased duration of the QRS-complexes and tented T-waves due to abrupt Ca2+-influx, contraction, and abrupt Ca2+ -binding (Fig. 24-3). Cardiac arrest occurs as ventricular fibrillation (the heart can never produce smooth tetanus) or as asystole. Insulin is used to drive K+ back into the cells - either by insulin infusion or by glucose infusion in order to release more insulin from the pancreatic islets. Usually, a combined
- 38. glucose-insulin drop is applied. Other hormones (adrenaline, aldosterone) also stimulate the Na+ -K+ -pump and thereby increase cellular K+ -influx (Fig. 24-3) Equations • The indicator dilution method: The indicator n mmol distributes in V litres of distribu- tion volume. We measure the concentration Cp in mM, following even distribution, and calculate the volume, V: Eq. 24-1: V = n/C p . (litre = mmol/(mmol/l) • When the tracer is radioactive potassium and thus distributed evenly in the exchangeable potassium pool, its specific Activity (SA) must be the same in urine, plasma or elsewhere in the pool. Eq. 24-2: Exchangeable body potassium = (Injected - eliminated)/SA. (Mol = Bq/(Bq per mol) We know the specific activity for the tracer (SA Bq per mol) from the plasma measurements. In this way we measure the exchangeable body potassium. The normal values are 41 mmol 39K per kg body weight for females, and 46 mmol per kg for males. • The following concentrations are found in normal plasma: [Na+ ] 135-145, [K+ ] 3.5-5, [Cl - ] 96-106, [bicarbonate] 24, and total-[Ca 2+] 2.5 mM. • The concentration of low molecular ions in the ultrafiltrate is affected by the Donnan effect (normally 5% for monovalent ions), and by the fractional content of water in plasma (0.94 normally): Eq. 24-3: [Low molecular ions] = Plasma conc. * Donnan factor/ 0.94. [Na+ ] = 141× 0.95/0.94 = 143 mmol/l of ultrafiltrate. Based on the Donnan effect alone, this result is less than 141. The Donnan effect on monovalent cations is simply more than compensated by the protein volume effect or fractional content of water in plasma (0.94). [Cl - ] = 103×1.05/0.94 = 115 mmol/l of ultrafiltrate. Based on the Donnan effect this result should be greater than 103 and the protein volume effect contribute further. Such an ultrafiltrate is present in the kidneys and in ISF. • The extracellular fluid volume (ECV) can be measured if all inulin molecules are collected in the urine over 10-15 hours after the inulin infusion stopped. Eq. 24-4: ECV = Amount of inulin excreted/(Cp /0.94). The inulin distribution volume is more or less identical to the ECV. • Concentration of molecules in the filtrate are calculated as follows: Eq. 24-5: Cfiltr = Cp ×Ffree /0.94 (mmol per l of ultrafiltrate). This value depends upon the fractional content of water in plasma (F water = 0.94 l of water per l of plasma) and of the fraction of free, unbound molecules (F free ). For uncharged, free molecules like inulin Ffree is 1, and for protein-bound molecules Ffree is lower than 1 Self-Assessment Multiple Choice Questions: Each of the following statements has True/False options: A. Hyponatraemia with normal ECV is often caused by stress, abnormally high ADH
- 39. release, increased sensitivity to ADH by drugs, or by intake of ADH-like substances. B. The total water content of a healthy person is 60%, and an extremely obese adult contains relatively more water. C. Hyponatraemia is defined as a plasma-[Na+ ] below 145 mM. D. A plasma- [K+ ] above 4.5 mM is life-threatening. E. An infusion of one l of 5% glucose is distributed evenly into all three compartments just as pure water. An infusion of one l of saline remains mainly in the ECV, whereas an infusion of one l of macrodex stays mainly in the vascular space. Case History A A healthy male with a body weight of 70 kg has a normal extracellular osmolality (300 mOsmol kg -1 ), and a normal ICV/ECV of 28/14 kg or l of water. One day he is the victim of severe burns and he suffers a water loss of 2.5 l of water (the salt loss is covered). 1. Calculate the new ECV osmolality following the water loss. 2. Does this hyperosmolality have consequences? 3. Following total restitution of the water compartments the patient undergoes surgery with skin grafts. During the long procedure he receives sufficient water by glucose infusion, but he looses 900 mOsmol NaCl. Calculate the new osmolality. 4. Is it dangerous for a healthy individual to lose 6 kg of water without solutes? 5. Is it dangerous for a healthy individual to lose 6 kg of water as an isosmolal fluid from the ECV? Case History B A female patient (age 22 years; weight 71 kg) is in hospital suspect of potassium imbalance. She has taken diuretics for 2 years. She is tired and sleepy; her legs are paretic. The ECG shows prolongation of the Q-T interval, depression of the S-T segments and flattening of the T-waves. Her blood pH is 7.57 and the serum K+ -concentration is 2.9 mM. One morning she receives an intravenous injection of a solution containing the radioactive isotope of potassium (555,000 Becquerel, Bq, of 42K+ with a physical half-life of 12 hours). Following the injection her urine is collected in two periods (0-12 and 12 -24 hours). The first urine collection contained 40 mmol K+ ( 39K+) and 4144 Bq 42K+. The second urine specimen contained 40 mmol K+ and 2220 Bq 42K+. Both urine specimens were analysed for radioactivity exactly 24 hours after the injection, where the specific activity of her plasma was 55.5 Bq/mmol. The 42K+, retained after the first 12 hours, distribute in her body just like all other exchangeable K+. The body contains traces (0.012% of the total) of naturally occurring radioactivity ( 40K) with a half-life of 1.3 × 109 years. 1. Calculate the exchangeable K+ pool of her body after the 12-hour distribution period. - Is the result normal? 2. Calculate the elimination rate constant (k) for exchangeable K + in her body, and the biological half-life for this K+ in hours. Calculate the ratio between the physical
- 40. and the biological half-life of K+ . 3. What is the cause of her disease? 4. Describe the actions of diuretics. 5. Describe a method for measurement of her total body potassium. Case History C This case requires knowledge of the renal function (Chapter 25). Two groups of substances are evenly distributed in the ECV of a healthy 25-year-old man. His weight is 70 kg, and his extracellular volume (ECV) is 14 L. Both groups of substances disappear solely by excretion through the kidneys. His GFR is 120 ml/min, and his renal plasma flow (RPF) is 700 ml/min. 1. Inulin is representative for one family of substances. Inulin is only ultrafiltered in the kidneys. What fraction (k 1 ) of the total amount of inulin in the body is maximally excreted in the urine per min? 2. The other substances are not only ultrafiltered, but they are also undergoing tubular secretion to such an extent that they totally disappear from the blood during the first passage. What is the elimination rate constant (k 2 ) for these substances? Try to solve the problems before looking up the answers. Highlights • Water permeable membranes separate the three body fluid compartments, so that they contain almost the same number of osmotically active particles (expressed as mOsmol per kg of water or the same freeze-point depression). The three compartments are the intracellular fluid volume (ICV), the interstitial fluid volume (ISV) and the vascular space. • The sum columns of electrolyte equivalents in muscle cells are essentially higher than the extracellular sum columns, because cells contain proteins, Ca2+ , Mg 2+ and other molecules with several charges per particle. • Females contain less water as an average compared to males. Such differences show sex dependency, but the important factor is the fraction of body fat, since fat tissue contains significantly less water than other tissues (only 10%). Sedentary, overweight persons contain 50-55 % water dependent on the body fat content, and regardless of sex. • Primary hyperaldosteronism (Conns hypercorticism disease) and all types of secondary hyperaldosteronism also lead to hypernatraemia combined with hypokalaemia and enlarged blood volume. Cerebral failure and convulsions are alarming signs, but there are no specific symptoms and signs of hypernatraemia. • Polyuria, polydipsia and thirst suggest diabetes insipidus and low urinary osmolality is a clear indication. Pituitary diabetes insipidus is treated with an analogue of ADH (desmopressin, with a low pressor-effect). • Regulation of K+-balance: The daily intake of K+ is matched by the renal K+- excretion and our daily urine contains 2-5 g of K+. • Acid-base balance. The pH of the ICV and the ECV is maintained within narrow limits
- 41. (many metabolic processes are sensitive to pH). The acid-base balance is accomplished by co-operative action of the kidneys and the lungs. • Hypokalaemia reduces the excitability of neurons, muscle cells and the myocardial syncytium. Thus, hypokalaemia can result in muscle weakness, paresis, and cardiac arrhythmias with ectopic beats and cardiac arrest in diastole. • Hyperkalaemia increases the excitability of neurons, muscle cells and the myocardium. • Acute hyperkalaemia is a normal condition following severe exercise, and normal kidneys easily eliminate this. In disease states the causes of hyperkalaemia are insufficient renal excretion or increased release from the body cells as during long lasting hunger. • A plasma- [K+] above 7 mM is life threatening due to ventricular fibrillation or cardiac arrest in systole. Tented T-waves and increased QRS-complexes characterise the ECG. Further Reading Astrup, P, P. Bie, and H.C. Engell. ‘Salt and water in culture and medicine.’ Munksgaard, Copenhagen, 1993. Knox, F. G. “Physiology of potassium balance.” Am.J. Physiol. 275 (Adv. Physiol. Educ. 20): S142-S147, 1998. Return to chapter 24 Return to Content
- 42. Section VI . The Kidneys And The Body Fluids This section was written following fruitful discussions with my colleagues Peter Bie, Niels-Henrik Holstein- Rathlou, Paul Leyssac, Finn Michael Karlsen, and medical students Margrethe Lynggaard and Mads Dalsgaard. The concept flux is net-transport of substance per time unit across an area unit. Flux is equal to concentration multiplied by flow or mol per time unit across a barrier area. - Frequently used abbreviations in this section are ECV f t ll l l ICV f i t l ll l ISF f i t titi l ti fl id d GFR f Chapter 25 Chapter 25. Renal Physiology and Disease Renal Physiology And Disease Study Objectives Principles Definitions Study Objectives Essentials • To define the concepts: Nephron, glomerular filtration, tubular secretion and Pathophysiology reabsorption, renal lobulus, renal plasma clearance, osmolar clearance, tubular passage Equations Self-Assessment fraction, reabsorption fraction, excretion fraction, filtration fraction, plasma extraction Answers fraction, proximal and distal system, glomerular propulsion pressure, net filtration Highlights pressure, renal threshold, and the maximal transfer (T max ) for tubular secretion and Further Reading reabsorption. Box 25-1 Box 25-2 • To describe the renal circulation and measurement of renal bloodflow, a superficial and Fig. 25-1 Fig. 25-2 a juxtamedullary nephron, the juxtaglomerular apparatus, and the concentrating Fig. 25-3 mechanism of the kidney. Fig. 25-4 Fig. 25-5 • To calculate the relation between half-life, elimination rate constant, clearance and Fig. 25-6 distribution volume of a substance treated in the kidneys. Fig. 25-7 Fig. 25-8 • To explain the normal renal function including the control functions, use of endogenous Fig. 25-9 Fig. 25-10 creatinine clearance as a renal test, the renal treatment of the filtration- reabsorption- Fig. 25-11 and secretion-families of substances, the glomerular filtration rate (GFR), the Fig. 25-12 angiotensin-renin-aldosterone cascade, the tubulo-glomerular feedback, the proximal Fig. 25-13 and distal transport processes, and micturition. To explain the pathophysiology of Fig. 25-14 common renal disorders including renal oedema. Fig. 25-15 Fig. 25-16 • To use the above concepts in problem solving and in case histories. Fig. 25-17 Fig. 25-18 Fig. 25-19 Principles Fig. 25-20 • The glomerulus and the proximal tubule are responsible for filtration of plasma and for Fig. 25-21 major reabsorption of water and solutes. Glomerular filtration is due to a Return to chapter 25 hydrostatic/colloid osmotic pressure gradient. Return to Content • Tubular reabsorption is the movement of water and solute from the tubular lumen to the tubule cells and often further on to the peritubular capillary network. • Tubular secretion represents the net addition of solute to the tubular fluid in the lumen. • All substances treated by the kidneys can be divided into three groups or families, namely the filtration group, the reabsorption group and the secretion group. Definitions • Anuria refers to a total stop of urine production frequently caused by circulatory failure with anoxic damage of the tubular system. • (Renal plasma) Clearance is a cleaning index for blood plasma passing the kidneys. The efficacy of this cleaning process is directly proportional to the excretion rate for the substance, and inversely proportional to its plasma concentration.
- 43. • Diuresis is an increased urine flow (ie, volume of urine produced per time unit). • Excretion fraction (EF) for a substance is the fraction of its glomerular filtration rate, which passes to and is excreted in the urine. • Extraction fraction (E) for a substance is the fraction extracted by glomerular filtration from the total amount of substance delivered to the kidney during one passage of the arterial blood plasma. • Free water clearance is the difference between urine flow and osmolar clearance (see below). The free water clearance is an indicator of the excretion of solute-free water by the kidneys. Excess water is excreted compared to solutes, when free-water clearance is positive. Excess solutes are excreted compared to water, when free-water clearance is negative. – Free water clearance is an estimate of the renal capacity for excretion of solute-free water. • Glomerular filtration is due to a hydrostatic/colloid osmotic pressure gradient - the Starling forces. • Glomerular filtration fraction (GFF) is the fraction of the plasma flowing to the kidneys that is ultrafiltered (GFR/RPF). GFF is normally 0.20 or 1/5. - The GFF is reduced during acute glomerulonephritis. • Glomerulonephritis is an autoimmune injury of the glomeruli of both kidneys. • Glomerular filtration rate (GFR) is the volume of glomerular filtrate produced per min. • Glomerular propulsion pressure in the blood of the glomerular capillaries is the hydrostatic minus the colloid osmotic pressure of the blood (ie, 2-3 kPa in a healthy resting person). • Glomerulo-tubular balance refers to the simultaneous increase in NaCl and water reabsorption in the proximal tubules as a result of an increase in GFR and filtration rate of NaCl. An almost constant fraction of salt and water is thus reabsorbed regardless of the size of GFR. • Nephron: A nephron consists of a glomerulus, a proximal tubule forming several coils (pars convoluta) before ending in a straight segment (pars recta), the thin part of the Henle loop and a distal tubule also with a pars recta and a pars convoluta. • The nephrotic syndrome refers to a serious increase in the permeability of the glomerular barrier to albumin, resulting in a marked loss of albumin in the urine. The albuminuria (more than 3 g per day) causes hypoalbuminaemia and generalized oedema. • Net ultrafiltration pressure is the pressure gradient governing the glomerular filtration - the net result of the so-called Starling forces (see Fig. 25-7). • Osmolar clearance is the plasma volume cleared of osmoles (solutes) each minute. – Osmolar clearance is also defined as the fictive urine flow that would have rendered the urine isosmolar with plasma. - Osmolar clearance is the difference between the urine flow and the free water clearance, and osmolar clearance estimates the renal capacity to excrete solutes. • Osmolarity is the amount of osmotically active particles dissolved in a litre of solution.
- 44. • Proximal tubule consists of the proximal convoluted tubule and pars recta. • Renal threshold for glucose is the blood glucose concentration at which the glucose can be first detected in the urine (appearance threshold) or at which the reabsorption capacities of all tubules are saturated (saturation threshold). • Renal ultrafiltrate is also compared to plasma water, because it is composed like plasma minus proteins. The fraction of one litre of plasma that is pure water is typically 0.94. Thus, the concentration of many substances in the ultrafiltrate, Cfiltr , is equal to Cp /0.94. • Single effect gradient is a transepithelial concentration gradient between the tubular fluid and the medullary interstitial fluid established at each level of the thick ascending limb by active NaCl reabsorption. • Tmax refers to the maximal net transfer rate of substance by tubular secretion or reabsorption. • Tubular passage fraction. The fraction of the amount ultrafiltered of substance passing a cross section of the nephron is the passage fraction. The passage fraction for inulin does not vary at all throughout the nephron. The passage fraction for inulin is one and remains so. • Tubular reabsorption fraction. The reabsorption fraction is the reverse of the passage fraction (1 minus the passage fraction). • Tubular reabsorption (active or passive) is the net movement of water and solute from the tubular lumen to the tubule cells and often further on into the peritubular capillary network. • Tubular secretion (active or passive) represents the net addition of solute to the tubular lumen. • Tubulo-glomerular feedback (TGF) controls the glomerular capillary pressure and the proximal tubular pressure – thus stabilising delivery of solute and volume to the distal nephron. The macula densa-TGF mechanism responds to disturbances in distal tubular fluid flow passing the macula densa. - Renal autoregulation is caused by myogenic feedback and by the macula densa-TGF mechanism. Essentials This paragraph deals with 1. The nephron, 2. Clearance and three clearance families, 3. Ultrafiltration and the inulin family, 4. Tubular reabsorption and the glucose family, 5. Tubular secretion and the PAH family, 6. Water and solute shunting by vasa recta, 7. Concentration or dilution of urine, 8. Renal bloodflow, 9. Macula densa-tubulo-glomerular feedback, 10. Non-ionic diffusion, 11. Tests for proximal and distal tubular function, 12. Stix testing with dipstics, and 13. Diuretics. 1. The nephron The kidneys transport substances by three vectorial processes. Vectorial processes are characterized by their direction and size only (Fig. 25-1). Fig. 25-1: Renal transport. Black arrows indicate three vectorial transporting processes in a nephron: 1. Glomerular ultrafiltration is caused by a hydrostatic/colloid osmotic pressure gradient (the Starling forces), 2. Tubular reabsorption is the net movement of water and solute from the tubular lumen to the tubule cells and to the peritubular capillaries, and 3. Tubular secretion represents the net addition of solute
- 45. to the tubular fluid. The final excretion rate of the substance s in the urine is called net-flux, J s , in Fig. 25-1. 1a. Nephron anatomy The functional unit is the nephron. Each human kidney contains 1 million units at birth. Each nephron consists of a glomerulus (ie, many glomerular capillaries in a Bowman's capsule), a proximal tubule forming several coils (pars convoluta) before ending in a straight segment (pars recta), the thin part of the Henle loop and a distal tubule also with a pars recta and a pars convoluta. The distal tubule ends in a collecting duct together with tubules from several other nephrons. The kidney (average normal weight 150 g) consists of a cortex and a medulla. The medulla is composed of renal pyramids, the base of which originates at the corticomedullary junction. Each pyramid consists of an inner zone (the papilla) and an outer zone. The outer zone is divided into the outer medullary ray and the inner ray. The rays consist of collecting ducts and thick ascending limbs of the nephron. A kidney lobulus is a medullary ray with adjacent cortical tissue. A kidney lobule is a pyramid with adjacent cortical tissue. The loop of Henle is a regulating unit. Actually, the Henle loop consists of the proximal pars recta, the thin Henle loop and the distal pars recta, which ends at the level of macula densa. The thin descending limb contains a water channel (called aquaporin 1) in both the luminal and the basolateral membrane. The last segment of the thick ascending limb is called the macula densa. The juxtaglomerular (JG) apparatus include the macula densa and granular cells of the afferent and efferent arterioles. Granular cells are modified smooth muscle cells that produce and release renin. The distal tubule is convoluted from the macula densa of the JG apparatus (Fig. 25-2). The illustration shows a collecting duct, which receives urine from many nephrons. Several collecting ducts join to empty through the duct of Bellini into a renal cup or calyx in the renal pelvis. The superficial nephron (represented on the left side of Fig. 25-2 A) does not reach the inner zone of the medulla, because its loop of Henle is short. These small, cortical nephrons have a smaller blood flow and glomerular filtration rate (GFR) than the deep, juxtamedullary nephrons (which are located close to the medulla and comprise 15% of all nephrons). The total inner surface area of all the glomerular capillaries is approximately 50- 100 m 2 . Mesangial and endothelial cells in the glomerulus secrete prostaglandins and exhibit phagocytosis. Many vasoconstrictors contract the mesangial cells, reduce the gomerular filtration coefficient (Kf – see later) and thus also GFR. The proximal tubules have an inner area of 25 m 2 due to characteristic microvilli or brush borders (containing carboanhydrase). Fig. 25-2: A: A superficial and a deep, juxtamedullary nephron leading to the same collecting duct. B: A juxtamedullary nephron with related blood vessels. The juxtamedullary nephron has a long, U-shaped Henle loop. The bottom of this loop extends towards the tip of the papilla (apex papillae) at the outlet of the collecting duct (Fig. 25-2). The juxtamedullary nephrons have large corpuscles with relatively large bloodflow. These nephrons also receive blood through afferent arterioles with large diameters, and return blood through efferent arterioles with small diameters. When the blood has passed the juxtamedullary glomeruli it continues to a primary capillary network and to the vasa recta in the medulla. The blood collects in vena arcuata, vena interlobaris and finally into vena renalis. 1b. The glomerular barrier
- 46. The filtration barrier of the glomerulus consists of capillary endothelium, basement membrane and the epithelial layer of Bowmans capsule consisting of podocytes with foot processes. The holes or fenestrae of the endothelium have a radius of approximately 40 nm (covered by a thin diaphragm) and are permeable to peptides and small protein molecules. The basement membrane consists of a network of fibrils permeable to water and small solutes. The podocytes cover the basement membrane with foot processes separated by gaps called split-pores through which the filtrate is retarded, because each split is covered by a membrane. All small ions and molecules with an effective radius below 1.8 nm (water, ions, glucose, inulin etc) filtrate freely. Substances with a radius of 1.8-4.2 nm are less filterable, and substances with a radius above 4.2 nm cannot cross the barrier. All channels of the glomerular barrier carry negatively charged molecules that facilitate the passage of positively charged molecules (eg, polycationic dextrans, Fig.25-3). Dextran macromolecules can be electrically neutral or they have negative (anionic) or positive (cationic) charges. Fig. 25-3: Filtration of dextran molecules across the glomerular barrier. The barrier contains glycoproteins with negative charges. Positive charged dextran molecules are attracted by the negative charges and filter easily. Positive charged molecules with an effective radius of 3 nm filter easier than negative charged molecules of the same size. These molecules can act as effective osmotic diuretics. Immunological or inflammatory damages of the glomerular barrier reduce the negative charge of the barrier. Hereby, negative protein molecules leave the plasma easier and proteinuria occurs in a number of glomerular disorders. 1c. Pregnancy and age The glomeruli grow and the size and weight of the kidneys increase during pregnancy, accompanied by increases in both renal bloodflow and filtration rate. The number of glomeruli and their tubules decrease with age. Drugs that are excreted by renal mechanisms can easily cause toxic accumulation in the elderly with poor kidney function. 2. Clearance In 1926 Poul Brandt Rehberg, an associate of August Krogh, found the muscle metabolite creatinine extremely concentrated in human urine (CU mg per ml) compared to plasma (CP mg per ml). He also measured the urine flow (urine production per min). Thus, the concentration index, CU /C P , is large for creatinine. Multiplying this index with the urine flow yields a result greater than similar results derived for most other substances (Eq. 25-1). Brandt Rehberg used this concept (later termed clearance) as his measure of renal filtration rate. The work with these matters developed into the idea of a filtration- reabsorption type of kidney. Rehberg was the first to realise that the reabsorption in the proximal tubules controls the filtration. A few years later Rehberg´s renal filtration rate was called creatinine clearance and used as a measure of the glomerular filtration rate (GFR). The renal plasma clearance is a cleaning index for blood plasma passing the kidneys. The efficacy of this cleaning process is directly proportional to the excretion rate for the substance and inversely proportional to its plasma concentration (Eq. 25-1). Clearance is the ratio between excretion rate and plasma concentration for the substance. Renal clearance can also be thought of as the volume of arterial plasma completely cleared of the substance in the kidneys within one min, or the number of ml arterial plasma containing the same amount of substance as contained in the urine flow per minute (Eq. 25-1). 2a. Glomerular filtration rate
- 47. The glomerular filtration rate, GFR, is the volume of glomerular filtrate produced per min. In healthy adults the GFR is remarkably constant about 180 l each day or 125 ml per min due to intrarenal control mechanisms. In many diseases the renal bloodflow, RBF, and GFR will fall, whereby the ability to eliminate waste products and to regulate body fluid volume and composition will decline. The degree of impaired renal function is shown by the measured GFR. GFR is routinely measured as the endogenous creatinine clearance. The endogenous creatinine production is from the creatine metabolism in muscles and proportional to the muscle mass. In a 70-kg person creatinine is produced at a constant rate of 1.2 mg per min (1730 mg daily). This production is remarkably constant from day to day, only slightly affected by a normal protein intake, and equal to the rate of creatinine excretion. Both the serum creatinine and the renal creatinine excretion fluctuate throughout the day. Therefore, it is necessary to collect the urine for 6-24 hours and measure the creatinine excretion rate (ie, the urine flow rate multiplied by the creatinine concentration in the urine). A single venous blood sample analysed for creatinine in plasma is all that is needed to provide the endogenous creatinine clearance (Eq. 25-1). Theoretically, two small errors disturb the picture, but both are overestimates. At the normally low plasma concentrations of creatinine, a modest tubular secretion of creatinine from the blood is detectable resulting in up to 15% overestimation of the creatinine excretion flux. Most laboratories measure creatinine in serum instead of plasma, which results in an overestimation of plasma creatinine. Thus, calculation of a fraction with both an overestimated nominator and denominator results in a value close to that of GFR in almost all situations, where the renal function is near normal. With progressive renal failure the plasma creatinine rises, and the creatinine secretion increases the nominator in the clearance expression even more, so the measured clearance will overestimate GFR. Still, the clearance provides a fair clinical estimate of the renal filtration capacity (GFR). In most cases a normal creatinine clearance (above 70 ml plasma per min at any age) is comparable with the normal range for serum creatinine (around 0.09 mM in Fig. 25-4). The serum creatinine concentration is inversely proportional to the creatinine clearance, and also a good estimate of GFR. Renal failure is almost always irreversible, when the serum creatinine is above 0.7 mM. Fig. 25-4: Creatinine clearance versus serum creatinine. – A low serum creatinine indicates normal kidney function, but not always (see false negative concentrations). – An elevated serum creatinine indicates kidney failure, but not always (see false positive concentrations). Serum [creatinine] and serum [urea] depend upon both protein turnover and kidney function. The serum [creatinine] and [urea] are large after intake of meals extremely rich in (fried) meat, although the kidney function is normal (false positive concentrations in Fig. 25-4). In some materials up to 15% of measured serum creatinine concentrations are normal, although the kidney function fails (false negative values in Fig. 25-4). Long-term hospitalisation often leads to muscular atrophy, which reduces creatinine production and excretion. The serum creatinine concentration is maintained normal because of a similar fall in kidney function (GFR). Half the osmolality of normal urine is due to urea, and the other half is mainly due to NaCl. The osmolarity of urine varies tremendously (from 50 to 1400 mOsmol per l). Physiological changes of the renal bloodflow often parallel changes of GFR. A reduced GFR implies a smaller tubular Na+ -reabsorption and thus a smaller O2 demand. When kidneys are perfused by anoxic blood the tubular reabsorption is blocked first, and then the
- 48. GFR is reduced. As tubular Na+ -reabsorption is the main oxidative energy demanding activity, a high GFR is correlated to high oxygen consumption in the normal kidney. The size of GFR is determined by the factors shown in Fig. 25-7. The resistance of the glomerular barrier is extremely small in healthy human kidneys. 2b. Inulin Inulin is the ideal indicator for determination of GFR, because of the following three relations: 1. Inulin is a polyfructose (from Jewish artichokes) without effect on GFR. Inulin has a spherical configuration and a molecular weight of 5000. Inulin filters freely through the glomerular barrier. Inulin is uncharged and not bound to proteins in plasma. Inulin crosses freely most capillaries and yet does not traverse the cell membrane (distribution volume is ECV). Since one litre of plasma contains around 0.94 l of water, the ultrafiltrate concentration of inulin is Cp /0.94. 2 All ultrafiltered inulin molecules pass to the urine. In other words, they are neither reabsorbed nor secreted in the tubules. Inulin is an exogenous substance - not synthesised or broken down in the body. 3. Inulin is non-toxic and easy to measure. Thus, under steady-state conditions, the rate of inulin leaving the Bowman's capsulesmust be exactly equal to the rate of inulin arriving in the final urine. The main idea is to measure the amount of inulin excreted in the urine during a timeperiod were the plasma [inulin] is maintained constant by constant infusion of inulin. After one hour the subject urinates, and the urine volume and inulin concentration in the urine and plasma is measured. The amount of inulin filtered through the glomerular barrier per min is: (GFR × Cp /0.94). All inulin molecules remain in the preurine until the subject urinates. Thus, the amountexcreted is equal to the amount filtered and Eq. 25-4 is developed (see later). Since the inulin clearance is 180 l per 24 hours for young, healthy males or 125 ml per min, the GFR must be (125 × 0.94) = 118 ml per min. The inulin clearance is 10% lower for young females than for young males due to the difference in average body weight and body surface area. The normal values for both sexes decrease with age to 70 ml per min after the age of 70. Inulin clearance is a precise experimental measure and the ideal standard, but inulin must be infused intravenously, and the method is not necessary in clinical routine. If the clearance of a substance has the same value as the inulin clearance for the person, then the substance is only subject to ultrafiltration. Theoretically, reabsorption might balance tubular secretion and give the same result. If the clearance of a substance is greater than the inulin clearance, then clearly this substance is being added to the urine as it flows along the tubules; in other words, it is being secreted. Similarly, if the clearance of a substance is less than the inulin clearance, it means that the substance is being reabsorbed at a higher rate than any possible secretion. The extracellular fluid volume (ECV) can be measured with inulin as inulin does not pass the cell membrane (see Chapter 24 and Eq. 24-4). The elimination of inulin is exponential - ie, the fraction (k) of the remaining amount in the body that disappears per time unit is constant (see Chapter 1). Since the filtration family of substances is eliminated from the blood solely by filtration, the elimination depends only on GFR, and the distribution volume is that of inulin (ECV). Thus, the elimination rate constant (k= 0.69/T½) for the inulin family is roughly equal to (GFR*C p )/(ECV*Cp ).
- 49. 2c. The three clearance-families All substances treated by the kidneys can be divided into three groups or families, namely the filtration-, the reabsorption-, and the secretion- family. The kidney treats the filtration family of substances (see later) just like inulin. The filtration rate (J filtr ) for inulin equals the excretion rate (J excr ), and both increase in direct proportion to the rise in Cp (Fig. 25-5). The clearance is the slope of the curve, and it is obviously a constant value that is independent of Cp . Fig. 25-5:The straight line shows a direct relationship between the filtration rate and the concentration for the inulin family of substances in plasma. The reabsorption or glucose family contains many vital substances (see later). For the reabsorption family of compounds, the excretion flux is equal to the filtration flux minus the reabsorption flux. The maximal reabsorption flux (T max ) is reached above a certain threshold. Above this saturation threshold the clearance for the reabsorption family is equal to (the inulin clearance - Tmax /C p ), according to the mathematical argument in Fig. 25-8. The secretion or PAH family comprises endogenous substances and drugs (see later). Foreign substances are often distributed in the ECV, but some of them are also entering cells (ICV). At low concentrations their elimination rate constant (k) is roughly equal to renal plasma flow (RPF) divided by ECV: ( RPF*C P /ECV*C P ) = RPF/ECV. Thus, k equals RPF/ECV or 1/20 min-1 in most healthy persons. The k value corresponds to a half- life of 14 min (T ½ = ln 2/k). 2d. Excretion rate and clearance. Excretion rate curves for inulin can be changed into clearance by a simple mathematical procedure: Differentiating the excretion flux curve for the inulin family with respect to Cp produce the renal plasma clearance curves for these substances. Let us assume that the curves are from a resting person in steady state with a normal inulin clearance (the slope of the line in Fig. 25-6,A). For the inulin family the excretion flux equals (urine flow × Cu ), and by division with Cp we have the inulin clearance. Fig. 25-6: A, B, and C are the filtration-reabsorption- and secretion-families of substances, respectively. - D shows the clearance curves. For all substances belonging to the inulin family the excretion flux curves are linear, so the rate of change (which is the clearance) must be constant in a given condition (Fig. 25-6A). The results of the three excretion fluxes are plotted with Cp as the dependent variable (x- axis of Fig. 25-6, ABC). The excretion flux curves for the three families of substances, when differentiated (dJ excr /dC p ), provide us with the three possible clearance curves (Fig. 25-6, D). For the reabsorption family, the clearance is zero at first, because the excretion is zero (Fig. 25-6 D). The clearance increases, and finally it approaches the inulin clearance. Therefore, the clearance is steadily increasing towards inulin clearance with increasing Cp . For the secretion family, the clearance must also be equal to the excretion flux divided by Cp . When the [PAH] increases, more and more PAH is eliminated by filtration, and the secretory elimination is relatively suppressed (so-called auto-suppression). The clearance for the secretion family is falling with increasing Cp , and approaches that of inulin (Fig. 25- 6 D).
- 50. Box 25-1: Composition of urine Daily renal Component Concentration Finding/Disease excretion <500 ml/Nephropathy, shock Water 500-2500 ml >2500 ml/Diabetes <20 mmol daily/Low diet Potassium 60-70 mM 90 mmol daily >150 mmol daily/Rich diet Sodium 50-120 mM 150 mmol daily Protein 20 mg*l-1 30-150 mg daily Microalbuminuria/Diabetes Proteinuria/Nephropathy Glucosuria/Diabetes mellitus Glucose zero Negligible Glucosuria/Proximal defect Urea 200-400mM 500 mmol daily High excretion/Uraemia High excretion/Large m. mass 1500-2000 mg Creatinine 0.1 daily Low excretion/Muscul. atrophy Osmolality >600 mOsmol*kg-1 Acceptable conc. capacity The composition of urine in Box 25-1 is the basis for simple diagnostics. Anuria or oliguria (<500 ml daily) indicates the presence of hypotension or renal disease. Polyuria (>2500 ml of urine daily) is the sign of diabetes – both diabetes mellitus and diabetes insipidus. Microalbuminuria (ie, 50-150 mg per l) indicates glomerular barrier disorder such as diabetic glomerular disease. Glucosuria with hyperglycaemia is the sign of diabetes mellitus, and without hyperglycaemia it is a sign of a proximal reabsorption defect. High urea excretion is seen in uraemia, and high creatinine excretion indicates a large muscle mass in a healthy person. A low creatinine excretion is the sign of muscular atrophy or ageing. 3. Ultrafiltation and the inulin family In a healthy person at rest almost 25% of cardiac output passes the two kidneys (1200 ml each min). The blood reaches the first part of the nephron through the afferent arteriole to the glomerular capillaries. In the glomerular capillaries the hydrostatic pressure is approximately 60 mmHg at the start and 55 mmHg at the end (Fig. 25-7). The inulin or filtration family consists of inulin, radioactive indicators( 51Cr-EDTA, 57Co- marked B12, 14C-marked inulin, 3 H-marked inulin, iothalamate marked with 125 I or 131 I), mannitol, raffinose, sucrose, thiocyanate, and thiosulfate. These substances are more or less evenly distributed in the ECV. 3a. The Starling forces The pressures governing the glomerular ultrafiltration rate (GFR) are called the Starling forces (see equation in Fig. 25-7). Normally, filtration continues throughout the entire length of the glomerular capillaries in humans, because the net ultrafiltration pressure (P net) is positive also at the efferent arteriole. The average values for determinants of GFR are given in the first equation of Fig. 25-7. The hydrostatic pressure gradient is an important
- 51. determinant of GFR. The glomerular filtration coefficient is called K f . The Kf is equal to the filtration surface area divided by the resistance of the glomerular barrier and thus a constant for a given barrier (Fig. 25-7). The value of K f (also called the reciprocal glomerular hydrodynamic resistance) is reduced in diabetes, glomerulonephritis and hypertension. Vasoactive substances constrict or dilatate the glomerular mesangial cells and change the value of Kf . In other conditions, the forces opposing filtration become equal to the forces favouring filtration at some point along the glomerular capillaries. This is called filtration equilibrium. The hydrostatic pressure in Bowmans space below the glomerular barrier is about 15 mmHg or 2 kPa (P Bow in Fig. 25-7). This pressure is almost equal to the proximal tubule pressure, since there is no measurable pressure fall along this segment. Fig. 25-7: Net ultrafiltration pressures in afferent and efferent end of glomerular capillaries. The Starling forces determine the final ultrafiltration pressure (Pnet ) across the glomerular barrier. There is almost no colloid-osmotic pressure in Bowmans space, but an oncotic pressure of approximately 25 mmHg in the incoming plasma, mainly due to proteins, which are up- concentrated, when fluid leaves the the plasma for Bowmans space. Hereby, the protein- oncotic pressure (pgc ) may increase from 25 to 35 mmHg at the end of the glomerular capillary (Fig. 25-7). The higher the renal plasma flow (RPF), the lower is the rise in pgc . A selective increase in the resistance of the afferent arteriole reduces both the RPF and the glomerular hydrostatic pressure (P gc ), but GFR decreases more than RPF, so the filtration fraction (= GFR/RPF) falls. In contrast, a rise in the resistance of the efferent arteriole reduces RPF but increases Pgc (Fig. 25-7). Instantly, GFR increases slightly, but GFR eventually decreases due to the rise in pgc . As RPF falls more than GFR the filtration fraction increases. A combined increase in both the afferent and the efferent arteriolar resistance (as caused by most vasoconstrictors) may also reduce RPF more than GFR, and increase the filtration fraction. 3b. The net ultrafiltration pressure The net ultrafiltration pressure (P net) varies from 20 to 5 mmHg through the glomerular capillaries, and provides the force for ultrafiltration of a fat- and protein- free fluid across the glomerular barrier into Bowmans space and flow through the renal tubules (Fig. 25-7). The ultrafiltrate is isosmolar with plasma, almost protein free, and contains low molecular substances in almost the same concentration as in plasma water. The proximal tubular reabsorption takes place through para- and trans-cellular pathways. In the peritubular capillaries, the Starling forces are seemingly adequate for capillary uptake of interstitial fluid (Fig. 25-7). The hydrostatic net pressure in the proximal tubules – and with it the GFR - is remarkably well maintained in spite of changes in proximal reabsorption of salt and water. An acute defect in the proximal reabsorption mechanism results in an initial rise in proximal hydrostatic pressure and the GFR is reduced. Due to autoregulation (see paragraph 9), the proximal hydrostatic pressure is rapidly normalised at a new steady state. Sympathetic stimulation increases both the proximal reabsorption rate and the peritubular capillary uptake (Fig. 25-7). Hereby, the hydrostatic pressure falls in the proximal tubules
- 52. and Bowman's capsule so GFR may increase. In reverse, angiotensin II secretion inhibits the proximal reabsorption rate, increases the proximal pressure and may reduce GFR. The total distal flow resistance below the proximal tubules (ie, in the distal system) is large and important. The distal resistance has two major components namely a high resistance in the Henle loop and an even higher resistance in the remaining distal system including the collecting ducts. The resistance of the glomerular barrier is calculated in Fig. 25-7 to be extremely small. Normally, there is hardly any hydrodynamic resistance to glomerular ultrafiltration. 4. Tubular reabsorption and the glucose family The reabsorption or glucose family contains vital substances such as glucose, amino acids, albumin, acetoacetates, ascorbic acid, beta-hydroxybutyrate, carboxylate, vitamins, lactate, pyruvate, Na+ , Cl - , HCO3 - , phosphate, sulphate and urea. 4a. Tubular handling of glucose Tmax is the maximum transfer or net reabsorption flux (J reabs ) for glucose (mol.wt. 180 g per mol) in the proximal tubules. The optimal value for this glucose transporter is 300 mg/min or 300/180 = 1.7 mmol/min for healthy, young subjects with a body weight of 70 kg. For the reabsorption family of substances, the excretion is zero at first since the entire filtered load is reabsorbed (all glucose is reabsorbed, see Fig. 25-8). The excretion flux increases then linearly with increasing filtration flux. Fig. 25-8: Renal Glucose rates as a function of the plasma concentration (Cp ). The appearance threshold is the blood plasma [glucose] at which the glucose can be first detected in the urine (normally 8.3 mM or 150 mg%). This occurs when most but not all nephrons are saturated (Fig. 25-8). The actual saturation threshold, the point where all nephrons are glucose-saturated, is much higher (normally above 13.3 mM). The concentration difference (13.3 - 8.3 = 5 mM) represents a similar reabsorption rate difference (1.7 - 1.0 = 0.7 mmol/min at normal GFR) called splay. The reabsorption capacity for glucose in the proximal tubule cells becomes saturated at these high blood concentrations (Fig. 25-8). 4b. Urea transport The water reabsorption in the proximal tubules increases the urea concentration in the fluid. Since urea is uncharged and diffuses easily, it will diffuse passively to the peritubular capillary blood. The passage fraction at the outlet of the proximal tubule is around 0.5 (50% of the filtered load). Urea is thus reabsorbed in the proximal tubules and also in the inner medullary collecting ducts and secreted in the thin descending and ascending limb of the Henle loop (see later). The kidney reuses urea by recirculation in the intra-renal urea recycling circuit: Inner medullary collecting ducts – medullary interstitium – loop of Henle – distal tubules – collecting ducts. The net reabsorption flux is around 50% of the filtration flux at normal urine flow. The normal urea concentration in plasma is 5mM, and the excretion flux for urea is proportional to this urea concentration. 4c. Proximal tubular reabsorption
- 53. Healthy proximal tubules reabsorb approximately 70% of the filtered water, Na+ , Cl - , K+ and other substances. The tubular passage fraction for these substances at the outlet of the proximal tubule is 0.3 (30%). The reabsorption of fluid is isosmotic. Almost all filtered glucose, peptides and amino acids are also reabsorbed by the proximal tubules. The Cl- reabsorption is passive. This ion follows the secondary active reabsorption of Na+ in order to maintain electrical neutrality. Reabsorption of water is passive as a result of the osmotic force created by the reabsorption of NaCl. All reabsorption processes are linked to the function of the basolateral Na+ -K+ -pump. The extremely high water permeability of the proximal tubule is essential for its nearly isosmotic volume reabsorption. The active reabsorption of solutes makes the fluid slightly dilute and the interstitial fluid slightly hypertonic. If inulin and PAH molecules are present their concentration in the fluid will rise (PAH also because of proximal secretion). The actively reabsorbed solutes have lower permeabilities (higher reflection coefficients) than NaCl. In the first half of the proximal tubule, Na+ - is reabsorbed with carbonic acid and organicmolecules belonging to the reabsorption family. - The proximal and distal reabsorption ofbicarbonate is already described in Chapter 17. Fig. 25-9: Reabsorption of NaCl in the early and the late part of the proximal tubule. CA stands for carboanhydrase in the brush borders of the cell. The reabsorption family of substances (X) enters the tubule cells by specific symporter proteins coupled to the Na+ -reabsorption (1.in Fig. 25-9). This is secondary active transport showing saturation kinetics. Na+ -reabsorption is also coupled to H+ -secretion from the cell by the function of the Na+ -H+-antiporter protein (2. in Fig. 25-9). This H+ - secretion is linked to bicarbonate reabsorption in the upper part of the proximal tubules. The driving force for the Na+ -entry is the Na+ -K+ -pump located in the basolateral membrane, which extrudes the Na+ to the intercellular space and the blood (3. in Fig. 25- 9). Glucose is a typical example. The luminal membrane contains a sodium-glucose- cotransporter (SGLT 2). A genetic defect in this protein produces familial renal glucosuria – just as a genetic defect in a similar intestinal protein (SGLT 1) produces glucose- galactose malabsorption. - The passage of glucose across the basolateral membrane is by carrier-mediated (facilitated) diffusion. In the second half of the proximal tubule, Na+ is reabsorbed together with Cl - across the cell membrane or through paracellular routes (Fig. 25-9, below). In this segment the tubular fluid contains a high concentration of Cl - and a minimum of organic molecules. Na+ crosses the luminal membrane by the operation of Na+-H+-antiporters and Cl - -anion antiporters. In the tubular lumen the secreted H+ and anion form a H+ -anion complex. The accumulation of a lipid-soluble H+ -anion-complex establishes a concentration gradient that allows H+-anion-complex recycling (Fig. 25-9). Transfer of the Cl - -ion from the tubular fluid to the blood causes the tubular fluid to become positively charged relative to the blood. 4d. Reabsorption in the thick ascending limb The Na+ -K+ -pump maintains a low intracellular Na+ , which drives the simultaneous, electroneutral reabsorption of 1 Na+ , 1 K+ , and 2 Cl - by the luminal Na+-K+-2Cl - - symporter. The Cl - -channels are only located in the basolateral membrane, so accumulated Cl - reaches the ISF. The K+ -channels are located in all membranes and K+ recirculates (Fig. 25-10). Paracellular reabsorption of positive ions by diffusion is augmented by the
- 54. positive charge of the tubular fluid (Fig. 25-10). The secondary active reabsorption of Na+ (and Cl-) is the basis for the transepithelial single effect gradient at each transverse level of the thick ascending limb (see later). Fig. 25-10: Reabsorption of NaCl in the thick ascending limb of the Henle loop. There is a luminal Na+ K + -2Cl- -symporter and a basolateral Na+ K + -pump. This mechanism is essential for development of medullary hypertonicity by NaCl and thus for counter current mutiplication (see later). The electrochemical energy for the function of the basolateral Na+ K+ -pump is provided by its Na+ -K+ -ATPase. The pump throws Na+ into the peritubular fluid. The K + and Cl - ions leak out passively. The thick ascending limb is impermeable to water in the absence of ADH, and reabsorbs Na+ actively. Loop diuretics, which abolish the entire osmolar gradient in the outer renal medulla, inhibit the luminal Na+ K+-2Cl - -symporter of the thick ascending limb. 4e. Reabsorption in the distal tubule and collecting duct The distal tubule is divided into an early and a late segment, since the early segment reabsorbs NaCl and is impermeable to water (as the thick ascending limb), whereas the late segment functions more like the collecting duct. In the early segment, the NaCl transfer is mediated by a NaCl-symporter (Fig. 25-11). Na+ leaves the cell through the basolateral Na+ -K+ -pump, and Cl - leaves the cell by diffusion across the basolateral Cl - -channels. Only a small fraction of the glomerular filtrate reaches the distal tubules. Thiazide diuretics inhibit the NaCl-symporter. Fig. 25-11: Cellular transport processes in the distal tubule and collecting duct. The late segment is composed of two cell types just as the collecting ducts. The light principal cells reabsorb Na+ and secrete K+ . The Na+ -K+ -pump in the basolateral membrane draws Na+ out into the ISF and K+ into the principal cells (Fig. 25-11). These cells have special ion channels in the luminal membrane, which is permeable to Na+ , but also to K+ . The Na+ -uptake depolarises the luminal membrane (-70 mV) and makes the lumen electronegative (-12 mV) compared to the interstitial fluid (reference potential zero). K+ rapidly diffuses into the tubular fluid. This secretion of K+ into the tubular fluid from the principal cell is thus linked to the Na+ -reabsorption. The amount of Na+ reabsorbed in the distal tubule system is much less than in the proximal, but it can be increased by the adrenocortical hormone, aldosterone. Aldosterone is a mineralocorticoid, which promotes the reabsorption of Na+ (and thus Cl - ) and the secretion of K+ (and H+ ) in principal cells. Aldosterone enters the cell from the blood and binds to an intracellular receptor to form a complex. The complex increases the formation of membrane proteins including the Na+ - K+ -pump and the luminal Na+ -channels. This is the essential control mechanism for [K+ ] in the ECV. Secretion mainly occurs when the [K+ ] in the ECV is higher than normal. Aldosterone also promotes the reabsorption of Na+ (and thus Cl - ) and the secretion of K+ (and H+ ) in the collecting ducts of sweat and salivary glands just as in the principal cells of the distal tubules of the kidney. Aldosterone-antagonists inhibit all aldosterone effects. The dark intercalated cells secrete H+ across the luminal membrane and reabsorb K+ . Intercalated cells are mitochondrial-rich and most active in persons with a low K + -pool. + + +
- 55. The H -secretion by the H -pump is precisely determined by the [H ] in the ECV. The collecting duct contains principal and intercalated cells just as the late distal segment, but the intercalated cell disappears in the inner medullary collecting ducts. The luminal membrane of the principal cells in the collecting ducts can be regulated from nearly water-impermeable (in the absence of antidiuretic hormone, ADH) to water- permeable (in the presence of ADH). The hormone increases the water-permeability by insertion of water-channels called aquaporin 2. The water-channels are stored in cytoplasmic vesicles that fuse with the luminal membrane. The basolateral membrane of the principal cell contains other aquaporins and they remain water-permeable even in the absence of ADH. Mutations in the genes for these channel proteins cause nephrogenic diabetes insipidus. 5. Tubular secretion and the PAH family Substances secreted like PAH constitute the secretion or PAH family. The filtration flux (J filtr ) as usual increases in direct proportion to the rise in Cp (Fig. 25-12). Dividing the excretion flux for PAH with Cp provides us with the PAH clearance. The clearance is the slope of the excretion flux curve (Fig. 25-12). The secretion flux approaches a maximum (T max ). Most of the PAH molecules are free, but 10-20% are bound to plasma proteins. Fig. 25-12: Renal PAH net rates (fluxes or J) as a function of plasma concentration, Cp . Organic acids and bases secreted in the proximal tubules include endogenous substances and drugs. The endogenous substances include adrenaline, bile salts, cAMP, creatinine, dopamine, hippurates, noradrenaline, organic acids and bases, oxalate, prostaglandins, steroids and urate. The drugs comprise acetazolamine, amiloride, atropine, bumetanide, chlorothiazide, cimetidine, diodrast, furosemide, hydrochlorothiazide, morphine, nitrofurantoin, para-aminohippuric acid (PAH), penicillin, phenol red, probenecid, sulphonamides, and acetylsalicylic acid. The secretion is often competitive. All these substances have varying but high affinity to an organic acid-base secretory system in the proximal tubule cells showing saturation kinetics with a Tmax . The organic cation secretion is analogous to the anion secretion. 5a. Tubular handling of PAH Tmax is the maximum secretion rate for PAH in the tubules (Fig. 25-13). Normally, the Tmax is 0.40 mmol per min (80 mg/min) for PAH. At low PAH concentrations in the plasma (Fig. 25-13), the slope of the excretion rate curve is high (the clearance for PAH is high). Here the PAH clearance is an acceptable estimate of the minimal renal plasma flow (see effective RPF later), because the blood is almost cleared by one transit. The secretion flux is maximal, when the plasma-[PAH] is high enough to achieve saturation. The weak organic acids and bases mentioned above are similarly secreted into the proximal tubule, and have secretory Tmax -values just like PAH (Fig. 25-14). In humans of average size (with an average body surface area of 1.7 m 2 ), the Tmax for diodrast and phenol red average 57 and 36 mg/min, respectively. 5b. Tubular handling of urate The active reabsorption of urate ions is accomplished in the proximal tubules by an electroneutral Na+ -cotransport. The tubular reabsorptive capacity is normally far greater
- 56. than the amount delivered in the glomerular filtrate. Above a critical concentration in the ECV of about 0.42 mM, the urate precipitates in the form of uric acid crystals, provided the environment is acid. Precipitation in the joints is termed gout (arthritis urica), often affecting several joints. Urate ions are accumulated in the ECV of gout patients, and often also in patients with uraemia. High doses of probenecid compete with urate for the proximal reabsorption mechanism. Use of this drug to patients with acute gout increases the excretion of urate in the urine. The active secretion of urate ions occurs from the blood plasma to the tubular fluid by the organic acid-base secretory system, which has a low capacity for urate. Thus, the renal tubules have a capacity of both actively reabsorbing urate ions and actively secreting them. 5c. Tubular handling of creatinine Essentially all creatinine in the glomerular filtrate passes on and is excreted in the urine. The molecule is larger than that of urea, and none of it is reabsorbed. Contrary, creatinine is secreted into the proximal tubules, so that the creatinine concentration in the urine increases more than 100-fold. 5d. The secretion mechanism The molecules of the secretion family leave the blood plasma of the peritubular capillaries and binds to basolateral receptors with symporters on the tubule cell (Fig. 25-13). These channels are driven by energy from the basolateral Na+ -K+ -pump transporting the molecules against their chemical gradient across the basolateral membrane. Inside the cell the molecules accumulate until they can diffuse towards the luminal membrane. Here, an antiporter transfers the ions into the tubular fluid. All these molecules compete for transport, so intake of the drug probenecid can reduce the penicillin secretion loss. Fig. 25-13: Secretion of organic anions across the proximal tubules The luminal membrane contains specific receptor proteins for nutritive mono- and di- carboxylates. These receptor functions are also coupled to Na+ -transfer. 6. Water and solute shunting by vasa recta The normal perfusion of the renal medulla is typically 5-10% of RBF. This bloodflow is larger than the fluid flow through the loop of Henle. Both the vasa recta and the closely located loops of Henle (from juxtamedullary nephrons) consists of two parallel limbs with counter-current fluid flow in the medulla. Vasa recta are designed as a counter current bloodflow and act as water-solute shunts that protect the medullary hyperosmotic gradient. The endothelial lining of vasa recta is highly permeable for small molecules (water, urea, NaCl, oxygen and carbon dioxide). Vasa recta also serve as a nutritive source to the medulla. Vasa recta receive blood from the efferent arterioles and consequently have an elevated colloid osmotic pressure and reduced hydrostatic pressure (Fig. 25-14). The net force in these vascular loops favours net fluid reabsorption. Let us consider the situation with a hyperosmotic medullary gradient and ADH present, so a concentrated urine is produced. The blood in the descending limb of vasa recta is first passed on in the direction of increasing medullary osmolarity. Accordingly, this blood must gradually supply water to the hyperosmolar, interstitial fluid by passive osmosis, and passively reabsorb solutes (NaCl and urea) by diffusion. Hereby, the interstitium is temporarily diluted and the blood is concentrated. In the ascending portion the blood passes regions with falling osmolarity, and the blood gradually absorbs water osmotically and
- 57. delivers solutes to the interstitium by diffusion. The flow in the ascending vasa recta is larger than in the descending limb, because water from the Henle loop is also reabsorbed. Fig. 25-14: A: Passive counter-current exchange occurs in vasa recta, with diffusion of solutes along black arrows. Passive osmotic flux of water from the blood to the hyperosmolar interstitium occurs along stippled, blue arrows. – B: The active counter-current multiplier in the thick ascending limb with a single effect at each horizontal level. The gross effect of the passive counter-current exchange in the vasa recta is that of a water shunt passing the medullary tissue, whereas solutes recycle and thus are maintained in medulla. Water is shunted from limb to limb without disturbing the inner medulla. The passive counter-current exchange and low bloodflow through the vasa recta curtail the medullary hyperosmotic gradient (Fig. 25-14). The meagreness of the medullary blood flow, reduced by ADH, contribute to the maintenance of the medullary hyperosmotic gradient, but reduce the nutritive supply to the inner medulla. 7. Concentration or dilution of urine The thin ascending limb of Henle is impermeable for water, but highly permeable for NaCl and less so for urea. The thick ascending limb is also impermeable for water and also for urea. The water permeability of the cortical and medullary collecting ducts increase with increasing concentrations of antidiuretic hormone (ADH) in the peritubular blood. Concentration of urine. Initially, the osmolarity of the tubular fluid, the vasa recta blood, and the interstitial fluid is 300 mOsmol * l -1 . The ascending limb of the Henle loop is impermeable to water and actively transports NaCl from the preurine into the surrounding interstitium. Thus solute and fluid is separated and the tubular fluid becomes diluted. At each horizontal level of the thick ascending limb, a hyperosmotic gradient (a single effect) of typically 200 mOsmol * l -1 is established (Fig. 25-14B). Energy is necessary to establish the hyperosmotic gradient. The energy is from Skou´s basolateral Na+ -K+ -pump, working in conjunction with the Na+ -K+ -2Cl —symporter of the thick ascending limb (Fig. 25-10). The total osmolarity in the inner medullary interstitial tissue can be as high as 1400 mOsmol per l, when the urine is maximally concentrated. The renal cortex fluid is isotonic with the plasma. When the isotonic fluid from the proximal tubules passes down through the hypertonic medulla in the descending thin limb of the Henle loop, water moves out into the medullary interstitium by osmosis, making the tubular fluid concentrated. This is because the epithelial cells of the thin descending limb are highly permeable to water but less so to solutes (NaCl and urea). Water is reabsorbed and returned to the body via vasa recta and the renal veins. At the bend of the loop the fluid has an osmolarity equal to that of the surrounding medullary interstitial fluid. However, the tubular fluid has a greater concentration of NaCl and a smaller concentration of urea than the surroundings. In contrast to the thin and thick ascending limb, most cell membranes including those of the proximal tubules and the thin descending limb of the Henle loop, are water-permeable under all circumstances. This is because these cell membranes contain water-channel proteins called aquaporins. As new fluid enters the descending limb of the Henle loop, the hyperosmotic fluid in the bottom of the loop is pushed into the ascending limb, where NaCl is separated from water. The osmolarity of the isosmotic tubular fluid running into the thin descending loop of the outer medulla is 300 mOsmol*l-1 and the output to the distal tubule is 100 mOsmol*l-1
- 58. (Fig. 25-14, B). At the bottom of the Henle loop the osmolarity can increase to at least 1300 mOsmol*l-1 . In a steady state with continuous fluid flow the total osmotic gradient along the entire system is thus (1300 - 100) = 1200. The gradient along the entire system is 6 multiples of the 200 mOsmol*l-1 single effect gradient. The thick ascending limb is a counter-current multiplier with a high multiplication capacity. The NaCl is reabsorbed repeatedly in the thick ascending limb of the Henle loop. The passive counter-current exchange in the vasa recta and the active counter-current NaCl reabsorption in the thick ascending limb combine into a solute-water separator, when ADH is present. Another component in the maintenance of the medullary hyperosmotic gradient is addition of urea to the tubular fluid in the thin segment of the Henle loop. Urea is then trapped in the lumen, because all nephron segments, from the thick ascending limb through the outer medullary collecting duct, are impermeable to urea. As the tubular fluid flows through the distal tubules, cortical collecting ducts and outer medullary collecting ducts, its urea concentration rises progressively, because these segments are essentially urea-impermeable whether or not ADH is present. In the presence of ADH, water is reabsorbed but urea is not and the osmolarity of the fluid increases. The maximal osmolarity in the cortical collecting duct is up to 300 mOsmol*l-1 , which is equal to the surrounding interstitial fluid. The distal fluid contains much urea and less NaCl. In reverse, the inner medullary collecting duct cells have urea-transporters that are ADH-sensitive. Thus large amounts of urea are reabsorbed at low urine flows, and the inner medullary interstitial fluid is loaded with urea that diffuses back to the tubular fluid through the thin descending and ascending limb in this urea recycling process. Urea covers 700 and NaCl also 700 mOsmol*l-1 out of the total 1400. Without passive urea recycling, the medullary interstitial osmolarity contributed by NaCl would have to double and thus the energy demand. Without the medullary hypertonic gradient we would be unable to produce concentrated urine when water depleted. A high osmolarity in the medullary interstitium enhances passive water reabsorption when ADH is present. ADH increases the concentration of solutes in the collecting ducts, and reduces the loss of water. A hyperosmotic concentration – moving from 300 up to 1400 mOsmol*l-1 in the inner medulla - has established a large concentration gradient between the tubular and the interstitial fluid. In man, the maximal urine osmolarity – when ADH is high - is 1400 mOsmol*l -1 , which in a daily urine volume of 500 ml corresponds to a daily solute loss of up to 700 mOsmol. The small urine volume contains high concentrations of urea and nonreabsorbed or secreted solutes. Dilution of urine (large urine flow) In the absence of ADH, the distal tubules, cortical collecting ducts and outer medullary collecting ducts are impermeable to water. The osmolarity of the passing tubular fluid is reduced (towards 100 mOsmol*l-1 ) when we need a diluted urine. The medullary collecting duct reabsorbs NaCl (actively) and is slightly permeable to water and urea in the absence of ADH. The final urine – with small concentrations of NaCl and urea - has an osmolarity of 50-150 mOsmol*l-1 , with a volume of up to 10% of the daily GFR. When ADH is absent, the fluid leaving the distal tubules remains hypotonic. Large amounts of hypotonic urine would then flow into the renal pelvis (with an osmolarity down
- 59. towards 50 mOsmol* l-1 ). A daily solute loss of 700 mOsmol, under these conditions, implies a daily water loss of at least 14 l. 8. Renal bloodflow (RBF) The Fick's principle (mass balance principle) is used to measure the renal plasma clearance at low plasma [PAH] , since at low concentrations - the blood is almost cleared by one transit. Thus, the renal plasma clearance for PAH is almost equal to the renal plasma flow RPF in Eq. 25-5. The law of mass balance states that the infusion rate of PAH is equal to its excretion rate at steady state. Only one passage through the kidneys effectively eliminates PAH from the venous blood plasma at low [PAH]. A methodological short cut is to measure the [PAH] in the medial cubital vein only, instead of the true arterial [PAH] by arterial catheterisation. PAH clearance is an acceptable approximation called the effective renal plasma flow (ERPF). In a healthy, resting person the ERPF is 600-700 ml of plasma per min and lower than the RPF. The ERPF principle avoids complex invasive procedures such as catheterisations. The Tmax for PAH is also a valuable measure of the secreting tubular mass, because the proximal tubule cells are saturated with PAH at high plasma-[PAH]. The RBF falls drastically, when the mean arterial pressure is below 9.3 kPa (70 mmHg). The medullary bloodflow is always small in both absolute and relative terms. Any severe RBF reduction as in shock, easily leads to ischaemic damage of the medullary tissues resulting in papillary necrosis and ultimately to failure of renal function. During such pathophysiological conditions, prostaglandins (PGE2 and PGI2 ) are secreted from the mesangial and endothelial cells due to sympathetic stimulation. These prostaglandins dilatate the afferent and efferent glomerular arterioles and dampen the renal ischaemia caused by sympatho-adrenergic vasoconstriction. Both RBF and GFR show autoregulation following acute changes in the perfusion pressure within the physiological pressure range (Fig. 25-15). The renal autoregulation is mediated by myogenic feedback and by the macula densa-tubulo-glomerular feedback mechanism. Myogenic feedback is an intrinsic property of the smooth muscle cells of the afferent and efferent arterioles. The myogenic response allows preglomerular arterioles to sense changes in vessel wall tension (T) and respond with appropriate adjustments in arteriolar tone. Stretching of the cells by a rise in arterial transmural pressure (DP) elicits smooth muscle contraction in interlobular arteries and afferent arterioles (Fig. 25-15). During sleep the mean arterial pressure decreases 1-2 kPa, which would lower Pgc and GFR without autoregulation. Autoregulation with maintained RBF and GFR means that also the filtered load and the sodium excretion is maintained during sleep and variations in daily activities. The macula densa- TGF mechanism is described below. When the renal perfusion pressure rises, the cortical bloodflow is effectively autoregulated. However, during certain circumstances the papillary bloodflow may increase due to release of NO, prostaglandins, kinins or other factors. The increased medullary bloodflow increases the interstitial hydrostatic pressure and thus the resistance towards Na+ - reabsorption, whereby the Na+ -excretion increases. Sympathetic vasoconstriction reduces the renal perfusion pressure and thus the resting RBF. Increased renal sympathetic tone releases renin and enhances Na+ -reabsorption in the proximal and distal tubules via nerve fibres. At maximum exercise RBF falls to half the resting level. - RBF also drops during emotional stress and during haemorrhage.
- 60. Fig. 25-15: Pressure-flow relations in the kidney. The RBF curve shows autoregulation, and GFR follows the bloodflow. Noradrenaline/dopamine from adrenergic fibres and circulating adrenaline from the adrenal medulla, constrict the afferent and efferent glomerular arterioles, when the hormones are bound to a 1 -adrenergic receptors. This constriction decreases both RBF and GFR. Sympathetic stimulation releases renin from the granular JG-cells of the arterioles via b1 - adrenergic receptors. Activation of the adrenergic fibres enhanches the Na+ -reabsorption along the whole nephron. The normal 300-g's of kidney tissue receive a total bloodflow (RBF) of 1200 ml per min, which is 20-25% of the cardiac output at rest. Thus, on an average, RBF is 400 ml of blood per min and per 100-g kidney tissue. These units are actually called Flow Units (FU) or perfusion coefficients. The renal blood flow per weight unit is higher than any other major organ in the body. The renal cortex receives 90% of the total RBF, and only 5-10% reaches the outer medulla. The blood supply is at a minimum in the inner medulla, and the oxygen tensions falls off sharply in the papillary tissue. The medullary bloodflow can be reduced towards 1% by vasopressin. The counter current exchange of oxygen in vasa recta is a disadvantage to the renal papillae because their cells are last fed with oxygen by the blood. The inner cells meet their energy requirements primarily by anaerobic breakdown of glucose by glycolysis. The amount of energy obtained here is only 1/10 of the oxidative breakdown of 1 mol of glucose (2 888 kJ free energy). The cortical bloodflow is much larger than the medullary bloodflow. Here, 1/5 of the whole plasma stream passes the glomerular barrier by ultrafiltration and becomes preurine. Fortunately, we obtain the greater part of the energy required for cortical tubular transport by oxidative metabolism. 9. Macula densa-tubulo-glomerular feed-back (TGF) The macula densa-TGF mechanism responds to disturbances in distal tubular fluid flow passing the macula densa. The JG-apparatus includes 1) the renin-producing granular cells of the afferent and efferent arterioles, 2) the macula densa of the thick ascending limb, and 3) the extraglomerular mesangial cells connecting the afferent and the efferent arteriole (Fig. 25-16). Renin is described in paragraph 6 of Chapter 24. Fig. 25-16: The juxtaglomerular apparatus with renin secretion. Regulation of renal sodium excretion is described in paragraph 9 of Chapter 24. The TGF mechanism thus includes the renin-angiotensin II-aldosterone cascade (Fig. 24- 5). Prostaglandins, adenosine and NO can modulate the response. These renin responses are part of the autoregulation to maintain RBF and GFR normal. 10. Non-ionic diffusion Non-ionic diffusion is a passive tubular reabsorption of weak organic acids and bases, which are lipid-soluble in the undissociated or non-ionised state. In this state these compounds penetrate the lipid membrane of the tubule cell by diffusion. The tubule cells, however, are practically impermeable to the dissociated form of these compounds. Therefore, the ionic form of the weak acid or base is fixed in the tubular fluid and favoured for urinary excretion. A weak organic acid is mainly undissociated at low urinary pH, whereas an organic base is
- 61. more dissociated. In acid urine the reabsorption rate of weak organic acids is increased, whereas the reabsorption rate of weak organic bases is reduced. In alkaline urine the opposite situation prevails. Examples of weak acids showing this phenomenon are phenobarbital and procain (both with pK just below 7), NH 4 + , acetylsalicylic acid, and many other therapeutics. Weak bases are the doping substance, amphetamine, and many therapeutics. In rare cases of poisoning with weak bases, the patients are treated with infusions of ammonium chloride solutions or amino acid-HCl solutions, which acidifies the urine (see Chapter 17). In cases of poisoning with weak acids, some patients receive infusions of bicarbonate solutions, whereby alkalisation of the urine is instituted. 11. Tests for proximal and distal tubular function Several proximal tests are available. 1. About 30 g of plasma albumin passes through the glomerular barrier each day. Fortunately, most of this albumin is absorbed through the brush border of the proximal tubules by pinocytosis. Inside the cell the protein molecule is digested into amino acids, which are then absorbed by facilitated diffusion through the basolateral membrane. Proteins derived from proximal tubule cells, such as ß2 -microglobulin, are reabsorbed by the proximal tubules. If this protein is demonstrated by urine electrophoresis, a proximal reabsorption defect is present. This is also the case, when generalized aminoaciduria is present. 2. Glucosuria in the absence of hyperglycaemia indicates a proximal reabsorption defect of glucose, since all glucose is reabsorbed before the fluid reaches the end of the proximal tubules in the normal state. 3. The lithium clearance. The lithium ion, Li + , is filtered freely across the glomerular barrier, and its concentration in the ultrafiltrate is equal to that in plasma water. Lithium carbonate is used in the treatment of manic phases (catecholamine over-reaction) of manic depressive psychosis. A plasma concentration of 0.5-1 mM provides enough Li + to block membrane receptors on the neurons involved for catecholamine binding. Fig. 25-17: Lithium clearance used as a measure of the proximal reabsorption capacity in the nephron. Li + is reabsorbed isosmotically in the proximal tubules together with water and Na+ (Fig. 25-17). The amount of Li + that leaves the proximal tubules (pars recta) is equal to its excretion rate in the final urine. This is because there is practically no reabsorption or secretion of Li + distal to this location. Accordingly, a large lithium clearance depicts a low proximal lithium reabsorption, and thus a poor proximal tubular function at a given GFR. Normally, the passage fraction of Li + is 0.25-0.3 at the end of the proximal tubules and almost the same fraction passes into the urine. 4 Hypokalaemia combined with normal or increased renal K+ -excretion suggests a defective proximal K+ -reabsorption (see Chapter 24 or Box 25-1). 5 Secretion across the proximal tubules (PAH clearance). Tests of distal tubular function: 1. Renal concentrating capacity is easily estimated as osmolalities in morning plasma and urine. Normal plasma osmolality ranges over 275-290 mOsmol per kg, and a urine osmolality above 600 mOsmol per kg suggests an acceptable renal concentrating capacity (more accurate is a standardized water deprivation test). 2. Inability to lower urine pH below 5.3 despite a metabolic acidosis is indicative of
- 62. distal renal tubular acidosis (ie, a bicarbonate reabsorption defect). This is a rare inherited condition with failure of bicarbonate reabsorption in the distal tubules and the collecting ducts. The metabolic acidosis is instituted by the oral intake of 100 mg ammonium chloride per kg and confirmed by a pHa less than 7.35 with a negative base excess and [bicarbonate] below 21 mM. 3. NaCl reabsorption in the early part of the distal tubule dilutes the tubular fluid, because this segment is impermeable to water (Fig. 25-11). Thiazide diuretics inhibit the Na+-Cl- symporter protein that causes a measurable increase in NaCl excretion and in diuresis (Fig. 25-11). 12. Stix testing with dipstics Routine stix testing for blood, glucose, protein etc. is necessary for the clinical evaluation of renal patients. Reagent strips for red blood cells are extremely sensitive. Even a trivial bleeding from a small capillary results in a positive answer indicating the presence of a few red cells. In such cases microscopy is necessary. Microscopy of fresh urine reveals red cells in cases of bleeding from the urinary tract, and red-cell casts in cases of kidney bleeding as in glomerulonephritis. Since the concentration threshold in urine for most reagent strips is 150 mg albumin per litre (l), there is no reaction to the normal albumin concentration of 20 mg l -1 . Even 50-100 mg of protein is often excreted daily due to the upright posture and exercise. An early sign of diabetic glomerular leakage or nephropathy is microalbuminuria, which is defined as an albumin concentration of 50-150 mg per l of urine, and measured by radioimmunoassay (RIA). Some laboratories measure the Tamm-Horsefall glycoprotein, which is secreted from the cells of the thick ascending limb of Henle, and thus a normal constituent of urine. Bacteria in the urine produce nitrite from the urinary nitrate, and dipsticks easily demonstrate the nitrite. Urinary tract infection also results in white blood cells in the urine, and more than 10 cells per µl are abnormal. 13. Diuretics Diuretics are therapeutic agents that increase the production of urine. Diuretics are employed to enhance the excretion of salt and water in cases of cardiac oedema or arterial hypertension. The so-called natriuretics inhibit tubular Na+ -reabsorption, but since the secretion of K+ and H+ is also increased, the patient must have compensatory treatment. The sites of action for different groups of diuretics are shown in Fig. 25-18. 13 a. Carboanhydrase inhibitors (eg, acetazolamide) act on the carboanhydrase (CA) in the brush borders and inside the cells of the proximal tubules. Inhibition of the metallo-enzyme reduces the conversion of filtered bicarbonate to carbon dioxide. As a result, there is a high concentration of bicarbonate and sodium in the tubular fluid of the proximal tubules. Up to half of the bicarbonate normally reabsorbed is eliminated in the urine causing a high urine flow and a metabolic acidosis. Thus, these inhibitors are diuretics. They are mainly used in the treatment of open-angle glaucoma (ie, an intraocular pressure above 22 mmHg). Acetazolamide promotes the outflow of the aqueous humour and probably diminishes its isosmotic secretion. Fig. 25-18: Sites of action on the nephron of different groups of diuretics 13 b. Loop diuretics (bumetanide and furosemide) inhibit primarily the reabsorption of NaCl in the thick ascending limb of Henle by blocking the luminal Na+ -K+ -2Cl - - +
- 63. symporter. The reabsorption of NaCl, K and divalent cations is reduced, and also the medullary hypertonicity is decreased. Hereby, the distal system receives a much higher rate of NaCl, water in isotonic fluid, and K+ . The overall result is an increased excretion of NaCl, water, K+ and divalent cations. The patient’s plasma- [K+ ] should be checked regularly. 13 c. Thiazide diuretics (bendroflurazide, hydrochlorothiazide) act on the early part of the distal tubule by inhibiting the (Na+ - Cl - )-symporter. They increase K+ excretion by increased tubular flow rate. Thiazide and many other diuretics are secreted in the proximal tubules. This secretion inhibits the secretion of uric acid, so thiazide is contraindicated by gout. 13 d. Potassium-sparing diuretics (eg, amiloride) inhibit Na+ -reabsorption by inhibition of sensitive Na+ -channels in the principal cells of the distal tubules and collecting ducts. Hereby, they reduce the negative charge in the lumen and thus the K+ -secretion. Amiloride causes natriuresis and reduces urinary H+ - and K+ -excretion 13 e. Aldosterone-antagonists (eg, spironolactone) compete with aldosterone for receptor sites on principal cells. As aldosterone promotes Na+ -reabsorption and H+ / K+ -secretion, aldosterone-antagonists cause a natriuresis and reduce urinary H+ - and K+ -excretion. Aldosterone-antagonists are weak potassium-sparing diuretics, mainly used to reduce K + - excretion caused by thiazide or loop diuretics. 13 f. Angiotensin-converting-enzyme (ACE)-inhibitors (captopril, enapril and lisinopril) reversibly inhibit the production of angiotensin II, reduce systemic blood pressure, renal vascular resistance and K+ -secretion. ACE-inhibitors promote NaCl and water excretion. ACE-inhibitors increase RBF without much increase in GFR, because of a decrease in both afferent and efferent arteriolar resistance. The development of diabetic nephropathy can be markedly delayed by early reduction of blood pressure with ACE-inhibitors and by careful diabetic management. 13 g. Osmotically active diuretics are substances such as mannitol and dextrans. These substances retard the normal passive reabsorption of water in the proximal tubules. Osmotic therapy with mannitol is used in the treatment of cerebral oedema. Mannitol is a hexahydric alcohol related to mannose and an isomer of sorbitol. Mannitol passes freely through the glomerular barrier and has hardly any reabsorption in the renal tubules. Its presence in the tubular fluid increases flow according to the concentration of osmotically active particles, which inhibit reabsorption of water. The high flow of tubular fluid means that the excretion of Na+ is great - despite the rather low Na+ concentration. Mannitol may help to flush out tubular debris in shock with acute renal failure, but the results are controversial. Dextrans (ie, polysaccharides) have a powerful osmotic and diuretic effect. - The larger, molecules (macrodex) are seldom used as volume expanders during shock because of allergic reactions. Pathophysiology This paragraph deals with 1. Glomerulonephritis, 2. Renal insufficiency, 3. Acute tubular necrosis, 4. Diabetic nephropathy, 5. Nephrotic syndrome, 6. Urinary tract infection, 7. Tubulo-interstitial nephritis, 8. Gouty nephropathy, 9. Renal hypertension, 10. Urinary tract obstruction, and 11. Tumours of the kidney. The severity and cause of kidney disease is evaluated by measurement of the GFR.
- 64. 1. Glomerulonephritis Glomerulonephritis is an immunologically mediated injury of the glomeruli of both kidneys. The majority of patients suffer from postinfectious glomerulonephritis or immune complex nephritis. This is a disorder, where circulating antigen-antibody complexes are deposited in the glomeruli or free antigen is bound to antibodies trapped in the capillary network. Typically, the antigen is derived from Lancefield group Aß- haemolytic streptococci, but also other bacteria, viruses, parasites (malaria), and drugs may be the origin. A few patients produce antibodies against their own antigens (eg, host DNA in systemic lupus erythematosus, malignant tumour antigen, or anti-glomerular basement antibody, anti- GBM). The inflammation is an abnormal immune reaction often caused by repeated streptococcal tonsillitis. An insoluble antigen-antibody complex precipitates in the basement membrane of the glomerular capillaries. The cells of the glomeruli proliferate, and disease will of course reduce GFR and to some extent, the RBF (measured as PAH clearance). Thus the infection depresses the glomerular filtration fraction (GFF = GFR/RPF). The acute postinfectious glomerulonephritis occurs typically in a child, who has suffered from streptococcal tonsillitis a few weeks before. Haematuria, proteinuria, and oliguria characterise acute nephritis with salt-water retention causing oedemas and hypertension. Pulmonary oedema and hypertensive encephalopathy with fits is life threatening. Uraemia is a clinical syndrome dominated by retention of non-protein nitrogen (eg, urea, uric acid, NH 4 + creatinine and creatine). Uraemic patients generally exhibit hyperkalaemia (plasma- [K+ ] above 5.5 mM) and metabolic acidosis (pH below 7.35 and a negative base excess). This is due to the inadequate secretion of K+ , NH 4 + and H+ . In complete renal shutdown, the patient dies within 1-2 weeks without dialysis. Dialysis is mandatory with severe uraemia. When serum creatinine rises above 0.7 mM, renal insufficiency is usually terminal (Fig. 25-4). Recording of blood pressure and fluid balance with weighing is important in order to prevent hypertension and pulmonary oedema to develop into a life-threatening condition. Fig. 25-19: Post-streptococcal glomerulonephritis. The parietal and visceral epithelial cells of the glomeruli grow and proliferate, just as the mesangial cells (Fig. 25-19). This proliferation and the damage of the basement membrane with accumulation of insoluble complexes all impair the glomerular barrier and reduce the glomerular filtration rate (GFR). Production of cytokines and autocoids enhance the inflammation. Capillary injuries with reduction of the lumen also reduce the renal bloodflow (RBF) to some extent (Fig. 25-19). Children with poststreptococcal glomerulonephritis are treated with a course of penicillin - often with an excellent prognosis. Glomerulonephritis as a part of systemic lupus erythematosus (SLE) is frequent in female lupus patients - in particular during pregnancy, where hypertension may precipitate glomerular injuries. Oestrogens accelerate progression of SLE, and there is a genetic predisposition. In SLE there is hyperactivity of the B-cell system, which may involve any organ, but typically affects the kidneys, joints, serosal membranes and the skin (Chapter 32). The B-cell system releases many antibodies to host antigens both in and outside the cell nuclei (single- and double-stranded DNA, RNA, plasma proteins, cell surface
- 65. antigens, and nucleoproteins). Lymphocytotoxic antibodies are also liberated, which may explain the inhibition of the T-cell system. The most important autoantibodies are those against nuclear antigens. Accumulation of immune complexes with double-stranded DNA probably causes the glomerular lesions as well as vasculitis and synovitis. Fig. 25-20: Anti-GBM glomerulonephritis with anti-GBM of the IgG type. Complement is shown as a small circle. Anti-GBM glomerulonephritis is a seldom disorder, where the patient produces antibodies (IgG type) against his own basement membrane. The antibody is known as anti-GBM or anti-Glomerular Basement Membrane antibody. The antigen is localised both in the glomerular basement membrane and in the basement membrane of the alveolar capillaries. The histological picture is characterized by proliferation of both parietal epithelial cells, and mesangial cells (Fig. 25-20). The capillary basement membrane is disrupted, and there is red cells and fibrin in Bowmans space. The diagnosis is confirmed by identification of circulating anti-GBM (Y- shape in Fig. 25-20). Glomerulonephritis with pulmonary haemorrhage is termed Goodpastures syndrome. The recurrent haemoptyses can be life threatening. 2. Renal Insufficiency Renal insufficiency is a clinical condition, where the glomerular filtration rate is inadequate to clear the blood of nitrogenous substances classified as non-protein nitrogen (urea, uric acid, creatinine, and creatine). The retention of nonprotein nitrogen in the plasma water is called azotemia, and the clinical syndrome is called uraemia. The number of filtrating nephrons falls below 1/3 of normal, as determined by measurement of a GFR below 40 ml/min. Acute renal insufficiency accompanies extremely severe states of circulatory shock (prerenal cause). The prerenal causes are hypovolaemia with hypotension or impaired cardiac pump function or the combination. Also a large group of renal causes to failure occurs (Box 25-2). Finally, the postrenal causes are all types of urinary tract obstruction. Acute renal failure is a serious disorder, which leads to progressive uraemia and chronic renal insufficiency. Box 25-2. Causes of renal failure Prerenal Causes: Cardiogenic and hypovolaemic shock Renal Causes: ACE-inhibitors and NSAID´s impair renal autoregulation Fulminant hypertension. Renal artery stenosis and embolism Vasculitis in glomerular capillaries Renal vein thrombosis Toxic tubular damage (organic solvents, myoglobin, aminoglycosides, and X- ray contrast). Postrenal Causes: Urinary tract obstruction is caused by obstructions of the lumen, the wall and by pressure from outside Lumen: Tumours, calculus and blood clots within the lumen of the renal pelvis, ureter, and bladder
- 66. Wall: Strictures of the ureter, the ureterovesical region, urethra, and pinhole meatus. Congenital disorders such as megaureter, bladder neck obstruction, and urethral valve. Neuromuscular dysfunction in the urinary tract Pressure: Compression by tumours, aortic aneurysm, retroperitoneal fibrosis or gland enlargement, retrocaval ureter, prostate hypertrophy, phimosis, and diverticulitis. Two complications to chronic renal failure must be considered: 1. Renal osteodystrophy develops in patients with severe renal failure. The kidneys fail in producing sufficient 1,25-dihydroxy-cholecalciferol. This is active vitamin D or a potent steroid hormone. The active vitamin D metabolite stimulates the Ca2+-transport across the cell and mitochondrial membranes. Lack of active vitamin D has the following two effects: a. Poor gut absorption of dietary Ca2+, so that plasma [Ca2+] falls. b.The PTH release is stimulated, because the normal inhibitory effect of active vitamin D is lost. After some time a secondary hyperparathyroidism develops with increased resorption of calcium from bone and increased proximal tubular reabsorption of calcium in an attempt to correct the low serum calcium. The calcium release from bone results in osteomalacia and in osteoporosis. Osteomalacia or soft bones is the result of demineralisation of the osteoid matrix usually caused by insufficient active vitamin D. Osteoporosis or thin bones is characterized by a reduction in all components of the bones. 2. Normochromic, normocytic anaemia. When normal kidneys are perfused with hypoxaemic blood, the peritubular interstitial cells produce large amounts of the glycoprotein hormone, erythropoietin, with strong effect on erythrogenesis. Chronic renal failure leads to erythropoietin deficiency, and thus to anaemia, which is of the normochromic, normocytic type. Haemodialysis The aim of haemodialysis is to eliminate nitrogenous wastes in patients with renal failure, and maintain normal electrolyte concentrations, serum glucose and normal ECV. In other words, the haemodialyzer or artificial kidney mimics the normal renal excretion of waste products (Fig. 25-21) Fig. 25-21: An artificial kidney (dialyser) with an area of 1 m 2 and a membrane thickness of 10 µm. Blood from the patient is pumped through a container with series of semi-permeable membranes separating the blood from dialysate (Fig. 25-21). Dialysate is a mixture of purified water with salts, and glucose in a composition comparable to normal fasting plasma apart from proteins. Bicarbonate or acetate buffer is present at a concentration about 35 mM. Haemodialysis is performed with a bloodflow of 200-300 ml per min. The patient is often connected to the dialyzer by an arteriovenous shunt made by plastic cannulae between the radial artery and an adjacent vein. The arterial blood flows into the artificial kidney and after dialysis the blood is returned to the venous system (Fig. 25-21). Dialysate is pumped through the container at a rate of 500 ml each min.
- 67. A plastic shunt connects the two cannulae on the forearm between dialysis sessions, and the large arterial bloodflow is sufficient to avoid coagulation in the plast shunt. Also dual- lumen venous catheters placed centrally are in use. If the sodium concentration of the dialysate is too high, the patient complains of thirst and the arterial pressure starts to rise. Low dialysate calcium may result eventually in secondary hyperparathyroidism, whereas a high dialysate calcium concentration causes hypercalcaemia. An adult patient with acute renal failure (so-called shock kidney) requires 4 -5 hours dialysis 3 times a week. Renal Transplantation Fit patients with chronic renal failure are offered renal transplantation. Rejection of the transplant is due to complement-fixing antibodies in the blood, or later caused by cellular or humoral immunity. Rejection years after the transplantation is frequently caused by ischaemic damages of the kidney. Donation of a kidney leaves the donor with one kidney only. Immediately after the removal, the GFR of the patient falls to half its original value, because half the functioning nephrons have been removed. Soon, most individuals will increase their GFR towards normal values by compensatory work hypertrophia of the remaining kidney. The hypertrophia-factor is not known. Each remaining nephron must filter and excrete more osmotically active particles than before. 3. Acute Tubular Necrosis This disorder has haemodynamic or toxic causes. Cardiogenic and hypovolaemic shock cause acute renal failures just as renal vasoconstriction. Renal ischaemia leads to hypoxic damage, in particular damage of the renal medulla, which is especially susceptible to ischaemia, because of the normally relatively poor oxygenation. Ischaemic tubular damage also reduces the GFR further, because of reflex spasms of the afferent arterioles, and due to tubular blockage with accumulation of filtrate in the early part of the proximal tubules, and hypoxic damage of the proximal tubular reabsorption capacity. Loss of appetite and energy, nausea and vomiting, nocturia and polyuria characterise the condition. Only when the GFR is severely depressed there is oliguria. Even a GFR of only 1 ml each min, as a contrast to the normal 125 ml per min, may result in a daily urine flow of 1440 ml (1*1440 min daily), if there is a total loss of tubular reabsorption and no luminal obstruction. This urine flow is normal, but unfortunately based on an almost total loss of glomerular and tubular function. Sufficient regeneration of the tubular epithelium allows clinical recovery. Sometimes also the renal cortex is necrotic, and following healing of the injuries, the result is scarring with glomerulosclerosis. This condition is also found following radiation nephritis. 4. Diabetic nephropathy Diabetic nephropathy includes glomerulosclerosis, with thickening of the basement membrane and damage of the glomerular filter by disruption of the protein cross-linkages and glomerular hyperfiltration. Excess NO production reduces the afferent arteriolar resistance and increases the glomerular capillary pressure. The earliest evidence of glomerular damage may occur 5-15 years following diagnosis in the form of microalbuminuria. The patient later develops intermittent albuminuria followed by
- 68. persistent albuminuria. Diabetic nephropathy includes hypertension, persistent albuminuria, and a decline in GFR. One third of all insulin-dependent diabetics develop nephropathy. The mortality rate is high. The metabolic disturbance in diabetics causes hypertension and leaky renal glomeruli, but the mechanism remains uncertain. Ascending infections result in interstitial lesions and diabetes typically show hypertrophy and hyalinization of afferent and efferent arterioles. Obstruction of the renal bloodflow (ischaemia) leads to hypoxic damage of the renal tissue. The tenuous bloodflow to the renal papillae via the vasa recta explains why renal papillary necrosis is frequent in diabetics. Treatment with ACE- inhibitors reduce urinary albumin excretion. Prophylactic therapy also postpones the development of diabetic nephropathy and hypertension with persistent microalbuminuria. The effectiveness of this treatment suggests that relative oversecretion of angiotensin may be involved in the pathogenesis of diabetic nephropathy. 5. Nephrotic syndrome The nephrotic syndrome refers to a serious increase in the permeability of the glomerular barrier to albumin, resulting in a marked loss of albumin in the urine. The albuminuria (more than 3 g per day) causes hypoalbuminaemia and generalized oedema. The number and size of pores in the glomerular barrier increase due to disruption of protein-linkages. Negatively charged glycoproteins in the glomerular barrier repel negatively charged proteins. The amount of negatively charged glycoproteins is reduced in glomerular disease. Oedema is visible in the face - especially around the eyes. A serious but rare complication may develop when a large volume of fluid accumulates in the abdominal cavity as ascites. 6. Urinary Tract Infection Urination (micturition) is controlled by the micturition reflex. Stretch or contraction of the smooth muscles in the bladder wall is sensed by mechanoreceptors and signalled via the pelvic nerve to the sacral spinal cord. Increased parasympathetic tone (via pelvic nerves and muscarinic receptors) cause sustained bladder contraction. Normally, contraction of the bladder muscles by micturition almost completely empties the bladder. Recurrent infections of the urinary tract are frequent among females. Faecal bacteria are transferred to the periurethral region, and finally to the bladder via the short female urethra. Bladder urine is normally sterile owing to bladder mucosal factors and other local defence mechanisms. Bacteria adhere to the bladder epithelium and multiplicate, when defence mechanisms function insufficiently. Prolonged bladder catheterisation predisposes to bladder infection, and even a few days can be critical. The diagnosis bladder infection is based on more than 100 000 bacteria per ml of clean- catch mid-stream urine. Quite a few patients with significant bacteriuria do not develop nitrite enough to be shown by dipstick tests. Typical symptoms are frequent micturition (polyuria), painful voiding (dysuria), suprapubic pain and smelly urine perhaps with haematuria. Echerichia coli and other coliform bacteria cause the majority of urinary tract infections; these infections are treated successfully with antibiotics (amoxyllin, trimethoprim etc) either as a single shot or for longer periods. 7. Tubulo-Interstitial Nephritis Bacterial pyelonephritis typically causes interstitial inflammation of the kidneys, but the
- 69. interstitial inflammation is more often caused by a hypersensitivity reaction to drugs (antibiotics, phenacetin and non-steroid anti-inflammatory drugs, NSAIDs). Pyelonephritis begins in the renal pelvis, and then progresses into the renal medullary tissue. The essential function of the medulla is to concentrate the urine during water depletion. Therefore, in patients with pyelonephritis, the ability to concentrate the urine is abolished/decreased (isosthenuria/hyposthenuria). The ability to dilute the urine deteriorates also. Thus, in isosthenuria the urine is always isotonic with the plasma. The patient with acute nephritis has fever, skin rashes and acute renal failure with eosinophiluria and eosinophilia. First of all the offending drug must be withdrawn, and the renal failure may require dialysis. Chronic tubulo-interstitial nephritis is caused by pyelonephritis, NSAIDs, diabetes mellitus, hyperuricaemia, irradiation damage etc. The major problem is that long lasting consumption of large amounts of analgesics leads to terminal renal failure. Nephrotoxic analgesics must be abandoned. The patient presents with uraemia, albuminuria, polyuria, haematuria, anaemia, and most often a history of analgesic abuse. Papillary necrosis can be present with papillary tissue passed in the urine or obstructing the ureter or urethra. In patients with tubular damage of the renal medulla, the ability to concentrate the urine is abolished together with the ability to dilute the urine. Thus, the urine is always isotonic with the plasma (isosthenuria). The result is polyuria and salt wasting. As the inflammation progresses to the cortex also the glomerular filtration deteriorates with accumulation of non-protein nitrogen in the plasma water (azotaemia), and the clinical syndrome uraemia. An isolated damage of the Na+ -reabsorption (salt-losing nephritis) is a condition in which the disease processes are mainly due to dysfunction in the renal medulla. There is a marked loss of Na+ in the urine and seriously low ECV and blood volume (hypovolaemia with threat of imminent shock). Thus the patient must have a high salt intake to prevent shock and keep alive. 8. Gouty Nephropathy Acute hyperuraemic nephropathy occurs in patients, where the condition leads to rapid destruction of cell nuclei (at the start of treatment for malignant disorders or obesity). Large quantities of nucleoproteins are released, and the production of uric acid is increased. The urate concentration increases in the extracellular volume (ECV). Above a critical concentration of 420 mM, the urate precipitates in the form of uric acid crystals, provided the fluid is acid. This concentration threshold defines hyperuricaemia. Precipitation in the joints with pain is termed gout (arthritis urica), and precipitation of uric acid crystals also occurs in the tubules, the collecting ducts and the urinary tract. Normally, urate ions are actively reabsorbed in the proximal tubules by a Na+ -cotransport. Urate ions can also be actively secreted from the blood to the tubular fluid. Allopurinol is prescribed during radiotherapy or cytotoxic therapy. Acute cases are also treated with allopurinol and forced alkaline diuresis. Uric acid stones are found in patients with hyperuricaemia, and in patients secreting sufficient urate without hyperuricaemia. Calcium stones may be formed around a nucleus of uric acid crystals. 9. Renal Hypertension
- 70. Bilateral renal disease such as chronic glomerulonephritis is a frequent cause of hypertension (Chapter 12), whereas unilateral renal disease, such as renal artery stenosis, is a fairly seldom cause of hypertension. Stenosis (narrowing of the lumen) of one renal artery leads to renal hypotension with excess renin production (see below) and systemic (secondary) hypertension. Exposure to fluid loss, reduced glomerular propulsion pressure, and increased sympathetic activity releases renin from the juxtaglomerular cells in the afferent glomerular arteriole, so the renin-angiotensin-aldosterone cascade is triggered (Fig. 24-5). Angiotensin II stimulates the aldosterone liberation from zona glomerulosa of the adrenal cortex, and thus stimulates Na+ -reabsorption and K+ -secretion in the distal tubules. The result is salt and water retention with increase in blood volume and blood pressure. Angiotensin II also constricts arterioles, with an especially strong effect on the efferent renal arteriole. This reduces the renal bloodflow further and also the proximal reabsorption. The development of hypertension in high renin states is mainly due to salt-retention and systemic vasoconstriction. Stenosis of one renal artery does not always lead to increased erythrogenesis. Stenosis of the renal artery implies a small renal bloodflow, a small glomerular filtration and a small NaCl-reabsorption with a related small oxygen consumption on the affected side. As long as the renal oxygenation is sufficient, the erythropoietin production is normal. Severe renal artery stenosis implies renal ischaemia and hypoxia, which is probably always consequential with complications. A hypoxic kidney has a low creatinine and PAH clearance. A long-term increase in sodium intake results in changes of the kidney function. Surprisingly, the changes are similar in hypertensive and normotensive humans! Most people increase their ECV and GFR without changing the absolute reabsorption rate of Na+ and water in the proximal tubules. Therefore, the rise in filtration rate of Na+ and water will reach the loop of Henle and the distal tubule. The arterial blood pressure and heart rate is unaffected by the amount of sodium in the diet. The plasma concentrations of active renin (Fig. 24-7), angiotensin II and aldosterone decrease with increasing Na+ intake, but atrial natriuretic factor (ANF) and cyclic GMP increase. Arginine vasopressin (ADH) in plasma does not change. The reason why this increase in NaCl load to the loop of Henle is not counterbalanced by the TGF-system is due to resetting of the TGF-mechanism, so a contraction is avoided in spite of the increased salt load.These homeostatic reactions are all appropriate physiological responses in both healthy and hypertensive humans. A rare cause of renal hypertension is due to Liddles syndrome. This is an autosomal dominant defect characterised by severe hypertension, hypokalaemia and metabolic alkalosis. The syndrome is similar to primary hyperaldosteronism, but the renin-aldosterone concentration in plasma is not increased. Liddles syndrome is caused by mutation of the gene for the amiloride-sensitive Na+ -channel (Fig. 25-11), whereby the channel is wide open. The Na+ -entry depolarises the membrane and favours secretion of K+ and H+ . 10. Urinary Tract Obstruction Obstruction of the urinary tract may occur at any location, and cause dilatation of the above structures. The obstruction is localised within the lumen (stone, sloughed papilla, or tumour), within the wall (neuromuscular dysfunction, stricture, congenital urethral valve, or pin hole meatus), or pressure from the outside obstruct the tract (eg, tumours,
- 71. diverticulitis, aortic aneurysm, prostatic obstruction, retrocaval ureter). Stretching of the renal calyces as they collect urine promotes their pacemaker activity and initiate a peristaltic contraction along the smooth muscle syncytium of the urinary tract. Obstruction of the urinary tract for weeks may lead to irreversible damage of the renal function in particular when combined with infection. Obstruction of the upper urinary tract with backpressure damage of the kidney is especially dangerous. Kidney stone disease (nephrolithiasis) attacks only a few percent of the Western population at any time. Most stones in male patients are composed of calcium complexed with oxalate and phosphate, whereas magnesium ammonium phosphate/acetate stones are more common in females. Only a few percent of all renal stones are composed of uric acid crystals or cysteine (mainly in children). Calcium-containing and cysteine stones are radiopaque, whereas stones of pure uric acid are radiolucent. In the presence of infection with urea-splitting bacteria, urea is hydrolysed to form the strong base ammonium hydroxide: CO (NH 2 ) 2 + H2 O 2 NH 3 + CO 2 ; NH 3 + H2 O NH 4 + + OH - . Alkaline urine favours stone formation by crystallization in the supersaturated fluid. Magnesium ammonium phosphate stones are also termed mixed infection stones. Obstruction or spasm of the ureter causes reflex constriction around the stone with ureteric or renal colic pain. The pain is an excruciating flank pain, with radiation to the iliac fossa and the genitals. The wall of the ureter is innervated with sensory nerve fibres running in the pelvic nerves. Renal colic is considered to be one of the most severe pain experience known. Excretion urography and plain X-ray examination are important in the diagnosis of renal stone disease. Percutaneous nephrolithotomy, pyelolithotomy or ureterolithotomy can avoid many cutting operations. Also shock-wave disintegration is in use (lithotripsy). Nephrocalcinosis refers to diffuse renal calcification that is detectable on a plain abdominal X-ray. Patients with hypercalcaemia (eg, primary hyperparathyroidism, hypervitaminosis D, and sarcoidosis) or with hyperoxaluria precipitate calcium oxalate and calcium phosphate in the renal parenchyma. Patients with renal tubular acidosis fail to acidify their urine, which favour precipitation of calcium oxalate and phosphate. Abdominal radiography A plain X-ray can identify calcification at any site including the renal system. Intravenous pyelography An organic iodine-containing contrast substance is injected slowly. Serial X-rays are taken, while compression bands are applied to the abdomen in order to obstruct ureteral emptying. Hereby, the upper renal tract is distended by the excreted contrast medium. Following removal of the compression bands, the rate of excretion of contrast is studied with films before and after voiding. 11. Tumours of the Kidney Benign and malignant tumours occur in the kidney. Benign renal fibroma, cortical adenomas or simple cysts seldom cause symptoms and signs. Those of no clinical importance are found incidentally at autopsy. Juxtaglomerular cell tumours are seldom. They produce large amounts of renin, which causes hypertension.
- 72. Haemangiomas may bleed following trauma and cause fatal blood loss. Malignant renal tumours are nephroblastoma and renal cell carcinoma. Nephroblastoma (Wilms´ tumour) is the most frequent intraabdominal tumour in both girls and boys. It usually presents within the first three years of life. A large abdominal mass is found sometimes with signs of intestinal obstruction. The tumour grows rapidly and spread to the lungs. The diagnosis is confirmed with excretion urography, arteriography or scanning. Radiotherapy and chemotherapy, combined with nephrectomy have improved the long- term survival rate. Renal cell carcinoma (hypernephroma) accounts for more than 90% of all the malignant renal tumours in adults - in particular smokers. There is a strong association with a rare autosomal dominant inherited disease called Von Hippel-Lindau´ syndrome (haemangioblastomas in the cerebellum and the retina). The genetic locus is on chromosome 3p.The tumour arises from proximal tubular epithelium, and lies within the kidney, but the prognosis is worse, if the tumour penetrates the renal capsule. The tumour is often protruding and the neoplastic cells have an unusually clear cytoplasm. Renal cell carcinoma is a likely source of ectopic hormone production. Increased production of erythropoietin leads to erythrocytosis and polycythaemia. Release of a parathyroid-hormone-like substance leads to hyperparathyroidism and hypercalcaemia. Release of abnormal quantities of renin triggers the renin-angiotensin-aldosterone cascade and leads to systemic hypertension. Metastases to distant regions are frequently found in the lungs and in the bones (osteolytic metastases). Solitary tumours are treated by partial or total nephrectomy or with interferon. Equations • The plasma clearance is defined as follows: Eq. 25-1: Clearance = (Cu ×V° u ) /C p [(mg/ml)×(ml/min)/(mg/ml)= ml/min]. Clearance can also be thought of as the volume of arterial plasma containing the same amount of substance as contained in the urine flow per minute. • Excretion fraction (EF). EF for a substance is the fraction of its glomerular filtration flux, which passes to and is excreted in the urine. EF = J excr /J filtr Since J excr = (Cu ×V° u ) and J filtr =(GFR × Cfiltr ) it follows that: Eq. 25-2: EF = (Cu ×V° u ) /(GFR × Cfiltr ) Cfiltr is the concentration of the substance in the ultrafiltrate. The excretion fraction for inulin is one (1). Substances with an EF above one are subject to net secretion. Substances with an EF below one are subject to net reabsorption. • Extraction fraction (E). E for a substance is the fraction extracted by glomerular filtration from the total substance delivery to the kidney via renal blood plasma. Eq. 25-3: E = J filtr /J total = (Ca - Cvr)/C a. Substances with an E of one are cleared totally from the plasma during their first passage of the kidneys. Inulin has an extraction fraction of 1/5. PAH has an extraction fraction of 0.9.
- 73. • Inulin clearance. The flux of inulin filtered through the glomerular barrier per min is: (GFR × Cp /0.94). All inulin molecules remain in the preurine and is excreted in the final urine. Thus, the amount excreted is equal to the amount filtered: GFR × Cp /0,94 = (Cu ×V° u ) mmol/min Eq. 25-4: GFR = ((C u ×V° u ) /C p ) × 0.94 = CLEARANCEinulin × 0.94. • The Fick's principle (mass balance principle) is used to measure the renal plasma clearance at low plasma [PAH], since at low concentrations the blood is almost cleared (90%) by one transit. Thus the renal plasma clearance is equal to the effective renal plasma flow (ERPF): Eq. 25-5: ERPF = J excr /Cp ; RPF = ERPF/E PAH • The law of mass balance states that the delivery of PAH to the kidney is equal to its excretion rate at steady state. The Effective Renal Blood Flow (ERBF) is calculated by the help of a total body haematocrit (normally 0.45). If ERPF is measured to be 600 ml plasma per min, we can calculate ERBF: 600/(1 - 0.45) = 1090 ml whole blood per min at rest. This is 20-25 % of cardiac output. The true RBF is 10% higher than the measured ERBF (ie, 1200 compared to 1090 ml whole blood). Self-Assessment Multiple Choice Questions The following five statements have True/False options: A: The B-cell system releases antibodies to host antigens. B: The glomerular barrier facilitates the passage of negatively charged polyanionic macromolecules. C: Thiazide diuretics may have serious side effects such as hypercholesterolaemia, hyperglycaemia (eg, glucose intolerance), hyperuricaemia, hypokalaemia, and impotence. D: Loop diuretics inhibit the reabsorption of NaCl in the thick ascending limb of Henle – and proximal pars recta - by blocking the cotransport process in the luminal entry membrane. E: Aldosterone antagonists, such as spironolactone, act on the aldosterone receptors on the late distal tubule cell and inhibit the K + -excretion. Case History A A male office worker, 58 years of age, body weight 70 kg, suffers from insulin-dependent diabetes mellitus. The disorder is complicated with arterial hypertension, hypercholesterolaemia, albuminuria and open-angle glaucoma. The patient is in anti- hypertensive therapy with a ß-adrenergic antagonist. The open-angle glaucoma is treated with acetazolamide (a carboanhydrase-inhibitor used as a diuretic to reduce the intra- ocular pressure). Scanning of the kidneys show a normal picture with an estimated normal kidney weight of 300 g. During renal catheterisation, a renal arteriovenous oxygen content difference is measured to 15 ml per l of blood, and the renal bloodflow is 1.2 l (normal). – The first 3 questions necessitate pharmacological knowledge. 1. Is it recommendable to treat hypertensive complications to diabetes with ß-blockers? 2. Describe the effects of carboanhydrase-inhibitor- treatment.
- 74. 3. Are thiazide diuretics without risks when prescribed to diabetics? 4. Calculate the renal oxygen uptake. Calculate the renal oxygen uptake in percentage of the total oxygen uptake of 250 ml per min. 5. Calculate the kidney weight in percentage of the total body weight. 6. Is the renal bloodflow redundant compared to the renal oxygen consumption? Case History B A female patient (weight 57-kg) of 23 years, with an inherited defect in renal tubular function, has a lowered tubular threshold for glucose reabsorption. The patient has a blood- [glucose] of 1000 mg per litre, and just above this level glucose appears in the urine (her appearance threshold). The diuresis is 1.5 ml per min, the plasma -[creatinine] is 0.09 mM, and the urine [creatinine] is 6 mM. The normal blood-glucose level is 5-6 mM. 1. Is the above blood -[glucose] normal? 2. Calculate the creatinine clearance? 3. Calculate the glucose reabsorption at this glucose level and compare it to the normal maximal capacity: 1.78 mmol min-1 . 4. Is the appearance threshold defined above equal to the saturation threshold? Case History C A 14-year old girl has a history of previous upper respiratory tract infections, and is now treated for another sore throat (ie, tonsillitis and high fever) with ampicillin for 10 days. Two weeks later she returns to her general practitioner (GP) complaining of tender knee joints from playing handball. There is abdominal pain. The girl is obviously ill and has a higher blood pressure than normally (145/90 mmHg or 19.3/12.7 kPa). The tonsillitis is cured and there is no fever. The upper abdomen is tender. A freshly passes urine sample is examined with a combined quantitative stick test. There is found haematuria and albuminuria (300 mg l -1 ). 1. What is the cause of the arthritis? 2. What are the causes of the haematuria and albuminuria? 3. Does the GP admit the girl to a hospital? Case History D During her working hours a 24-year old nurse delivered an arterial sample for blood gas tensions. She had no symptoms or signs of disease, but doubted that an arterial sample could be taken without causing pain. The sample was taken from a radial artery with a fine needle following local anaesthesia and she experienced no pain. The arterial blood gas values were: CO 2 partial pressure 24 mmHg, O2 partial pressure 102 mmHg, pHa 7.36, and Base Excess - 8 mM. The nurse had been starving for 24 hours. 1. What was the explanation of her acid-base disturbance? 2. What was the rational treatment? Case History E A young female (body weight 56 kg) with an inulin clearance of 125 ml of plasma per min is tested with para-amino-hippuric acid (PAH). The free fraction of PAH in the plasma is
- 75. 0.80, and the rest binds to plasma proteins. Her urine is collected in a period and the excretion flux of PAH is measured to 100 mg each min. The average concentration of PAH in plasma from the renal arterial and venous blood is 0.2 and 0.02 g per l, respectively. The haematocrit is 43%. 1. Calculate the clearance for PAH. 2. Calculate the tubular secretion flux for PAH at the blood plasma concentration concerned. 3. Calculate the renal blood flow (RBF). The patient collects the urine in a second period, where the average concentration of PAH in plasma from the arterial blood is 1 g per l. The maximal tubular secretion rate for PAH is defined as Tmax for PAH and is 80 mg per min. 4. Calculate the excretion flux for PAH in the urine. 5. Calculate the new clearance for PAH. Try to solve the problems before looking up the answers Highlights • Creatinine clearance provides a fair clinical estimate of the renal filtration capacity. • The renal control of body fluid osmolality maintains the normal cell volume (ICV) by changes of renal water excretion. • Normally, we excrete 1500 (range: 1200-1800) ml of water and 2-5 g of Na+ (= 5-12 g NaCl) daily. • Renal excretion of waste products. Urea from amino acids is excreted with about 30 g or half a mol of urea per day. The daily renal excretion of uric acid, creatinine, hormone metabolites and haemoglobin derivatives matches their daily production. • The daily renal excretion of metabolic intermediates and foreign molecules (drugs, toxins, chemicals, and pesticides) is carefully matched to the intake or production. • Secretion of hormones: The kidney secretes erythropoietin, renin, kinins, prostaglandins and 1,25-dihydroxy-cholecalciferol. • Acute Tubular Necrosis has haemodynamic or toxic causes. Cardiogenic and hypovolaemic shock cause acute renal failures just as renal vasoconstriction. Renal ischaemia leads to hypoxic damage, in particular damage of the renal medulla. Ischaemic tubular damage also reduces the GFR further, because of reflex spasms of the afferent arterioles, and due to tubular blockage with accumulation of filtrate in the early part of the proximal tubules. • Bacterial pyelonephritis typically causes interstitial inflammation of the kidneys, but the interstitial inflammation is more often caused by a hypersensitivity reaction to drugs (antibiotics, phenacetin and non-steroid anti-inflammatory drugs, NSAIDs). • Diabetic nephropathy includes hypertension, albuminuria and low GFR with glomerulosclerosis (thickening of the basement membrane and damage of the glomerular filter by disruption of the protein cross-linkages). The earliest evidence may be microalbuminuria. The patient later develops intermittent albuminuria followed by
- 76. persistent albuminuria. • Nephroblastoma (Wilms´ tumour) is the most frequent intraabdominal tumour in both girls and boys. A large abdominal mass is found sometimes with signs of intestinal obstruction. The tumour grows rapidly and spread to the lungs. The diagnosis is confirmed with excretion urography and arteriography. • Renal cell carcinoma (hypernephroma) accounts for more than 90% of all the malignant renal tumours in adults (smokers). There is a strong association with a rare autosomal dominant inherited disease called Von Hippel-Lindau syndrome (haemangioblastomas in the cerebellum and the retina). The genetic locus is on chromosome 3p. Further Reading Nephron. Monthly journal published by the International Society of Neprology. S Karger AG, Allschwilerstrasse 10, PO Box CH-4009 Basel, Switzerland. Rehberg, P. Brandt. "Studies on kidney function: I. The rate of filtration and reabsorption in the human kidney." Biochem. J. 20: 447, 1926. Schafer, JA. Renal water and ion transport systems. Am. J. Physiol. 275 (Adv. Physiol. Educ. 20): S119-S131, 1998. Return to chapter 25 Return to Content
- 83. Seasonal Influenza Vaccine Supply for the U.S. 2009-10 Influenza Season How much influenza vaccine is projected to be available for the 2009-10 influenza season? At the current time, six influenza vaccine manufacturers are projecting that as many as 114-115 million doses of influenza vaccine will be available from currently licensed manufacturers in the U.S. for use during the 2009-10 influenza season. How much thimerosal-free influenza vaccine is expected to be available for the 2009-10 season? For the 2009-10 season, manufacturers project producing approximately 50 million doses of thimerosal-free or preservative-free (trace thimerosal) influenza vaccine. Can I still buy influenza vaccine for the 2009-10 season? Influenza vaccine pre-booking typically occurs between January and March, though most preparations of vaccine should still be available for purchase. Providers should contact distributors and local vendors about remaining supply. Information about distributors who still have influenza vaccine available for sale can be found at http://www.preventinfluenza.org/ivats/ . What can we anticipate in terms of the timing of vaccine availability for the 2009-10 season? Distribution of most products began in early to mid-August and manufacturer projections indicate that the vast majority of vaccine will be distributed by the end of October. However, some vaccine distribution may continue into November, including doses that are ordered during the fall. Are all influenza vaccines the same? Different influenza vaccine preparations have different indications as licensed by the FDA. See the table below for an overview of these indications. TABLE. Seasonal Influenza Vaccine Manufacturers for the 2009- 2010 Influenza Season Manufacturer Vaccine Formulation Thimerosal Age preservative indication sanofi pasteur, Fluzone®, Multi-dose Yes 6 months Inc. Inactivated vial and older TIV Single-dose None 6-35 pre-filled 0.25 months mL syringe Single-dose None 36 months pre-filled 0.5 and older mL syringe or vial Novartis Vaccine Fluvirin® Multi-dose Yes 4 years and (formerly Inactivated vial older Chiron TIV Single-dose Preservative 4 years and Corporation) pre-filled free (1 mcg or older 0.5mL syringe less mercury/0.5mL
- 84. dose) MedImmune FluMist® Single-dose None Healthy* Vaccines, Inc. LAIV sprayer persons 2- 49 years CSL Afluria® Single-dose None 18 years Biotherapies Inactivated pre-filled and older TIV 0.5mL syringe Multi-dose Yes 18 years vial and older GlaxoSmithKline Fluarix™ Single-dose Preservative 18 years Biologicals Inactivated pre-filled 0.5 free (1 mcg or and older (subsidiary of TIV mL syringe less GlaxoSmithKline mercury/0.5mL PLC) dose) ID Biomedical FluLaval™ Multi-dose Yes 18 years Corporation Inactivated vial and older (subsidiary of TIV GlaxoSmithKline PLC) Flu Clinic Locators Open To The Public ALA Flu Clinic Locator CDC spreadsheet of public health department clinics September 29, 2009 * "Healthy" indicates persons who do not have an underlying medical condition that predisposes them to influenza complications. Page last reviewed: July 20, 2009 Page last updated: July 20, 2009 Content source: Centers for Disease Control and Prevention Centers for Disease Control and Prevention 1600 Clifton Rd. Atlanta, GA 30333, USA 800-CDC-INFO (800-232-4636) TTY: (888) 232-6348, 24 Hours/Every Day - cdcinfo@cdc.gov s.pageName=document.title; s.channel="CDC Flu"; siteCatalyst.setLevel1("AllFlu"); siteCatalyst.setLevel2("Flu"); siteCatalyst.setLevel4("Seasonal Flu - Content Pages: Healthcare Providers");
- 85. QUESTIONS & ANSWERS Influenza Diagnostic Testing During the 2009-2010 Flu Season September 29, 2009, 6:00 PM ET For the Public How will I know if I have the flu this season? You may have the flu if you have one or more of these symptoms: fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, fatigue and sometimes, diarrhea and vomiting. Most people with 2009 H1N1 have had mild illness and have not needed medical care or antiviral drugs, and the same is true of seasonal flu. (More information is available on What To Do If You Get Sick this flu season.) Most people with flu symptoms do not need a test for 2009 H1N1 because the test results usually do not change how you are treated. How can I know for certain if I have the flu this season? To know for certain, a test specific for flu would need to be performed. But most people with flu symptoms do not need a test for 2009 H1N1 flu because the test results usually does not change how you are treated. What kinds of flu tests are there? A number of flu tests are available to detect influenza viruses. The most common are called “rapid influenza diagnostic tests” that can be used in outpatient settings. These tests can provide results in 30 minutes or less. Unfortunately, the ability of these tests to detect the flu can vary greatly. Therefore, you could still have the flu, even though your rapid test result is negative. In addition to rapid tests, there are several more accurate and sensitive flu tests available that must be performed in specialized laboratories, such as those found in hospitals or state public health laboratories. All of these tests are performed by a health care provider using a swab to swipe the inside of your nose or the back of your throat. These tests do not require a blood sample. For more information, see Seasonal Influenza Testing. How well can these tests detect the flu? Rapid tests vary in their ability to detect flu viruses. Depending on the test used, their ability to detect 2009 H1N1 flu can range from 10% to 70%. This means that some people with a 2009 H1N1 flu infection have had a negative rapid test result. (This situation is called a false negative test result.) Rapid tests appear to be better at detecting flu in children than adults. None of the rapid tests currently approved by the Food and Drug Administration (FDA) are able to distinguish 2009 H1N1 flu from other flu viruses. Will my health care provider test me for flu if I have flu-like symptoms? Not necessarily. Your health care provider may diagnose you with flu based on your symptoms and their clinical judgment or they may choose to use an influenza diagnostic test. Depending on their clinical judgment and your symptoms, your healthcare provider will decide whether testing is needed and what type of test to perform. CDC has provided recommendations for clinicians this season to help with testing decisions. This season, most testing will be done in people who are seriously ill (hospitalized patients) and patients where testing may impact treatment decisions. In most cases, if a healthcare provider suspects you have the flu, the test results will not change their treatment decisions. Who is being tested for flu this season? This season CDC has provided Interim Recommendations for Clinical Use of Influenza Diagnostic Tests During the 2009-10 Influenza Season which recommends that the following people receive influenza diagnostic testing: 1) people who are hospitalized with suspected flu and 2) people such as pregnant women or people with weakened immune systems, for whom a diagnosis of flu will help their doctor make decisions about their care. CDC expects that most people with flu symptoms this season will not require testing for 2009 H1N1 because the test results
- 87. QUESTIONS & ANSWERS 2009 H1N1 Influenza Vaccine November 13, 2009, 12:30 PM ET 2009 H1N1 Recommendations Who will be recommended to receive the 2009 H1N1 vaccine? CDC’s Advisory Committee on Immunization Practices (ACIP) recommends that certain groups of the population receive the 2009 H1N1 vaccine first. These target groups include pregnant women, people who live with or care for children younger than 6 months of age, healthcare and emergency medical services personnel, persons between the ages of 6 months and 24 years old, and people ages of 25 through 64 years of age who are at higher risk for 2009 H1N1 because of chronic health disorders or compromised immune systems. The Advisory Committee on Immunization Practices (ACIP) has issued separate recommendations on Who Should Get Vaccinated Against Seasonal Flu. Vaccine to protect against the 2009 H1N1 flu virus is available; however, initial supplies are limited. The Advisory Committee on Immunization Practices (ACIP) has recommended that the following groups receive the vaccine before others: pregnant women, people who live with or care for children younger than 6 months of age, health care and emergency medical services personnel with direct patient contact, children 6 months through 4 years of age, and children, especially those younger than 5 years of age and those who have high risk medical conditions are at increased risk of influenza-related complications. For a more detailed description of children at highest risk, read Children with Developmental Disabilities and Chronic Medical Conditions The committee recognized the need to assess supply and demand issues at the local level. The committee further recommended that once the demand for vaccine for these target groups has been met at the local level, programs and providers should begin vaccinating everyone from ages 25 through 64 years. Current studies indicate the risk for infection among persons age 65 or older is less than the risk for younger age groups. Therefore, as vaccine supply and demand for vaccine among younger age groups is being met, programs and providers should offer vaccination to people over the age of 65. How many doses of vaccine are required? The U.S. Food and Drug Administration (FDA) has approved the use of one dose of 2009 H1N1 flu vaccine for persons 10 years of age and older. This is slightly different from CDC’s recommendations for seasonal influenza vaccination which states that children younger than 9 who are being vaccinated against influenza for the first time need to receive two doses. Infants younger than 6 months of age are too young to get the 2009 H1N1 and seasonal flu vaccines. What is the recommended interval between the first and second dose for children 9 years of age and under? CDC recommends that the two doses of 2009 H1N1 vaccine be separated by 4 weeks. However, if the second dose is separated from the first dose by at least 21 days, the second dose can be considered valid. Do those that have been previously vaccinated against the 1976 swine influenza need to get vaccinated against the 2009 H1N1 influenza? The 1976 swine flu virus and the 2009 H1N1 virus are different enough that it's unlikely a person vaccinated in 1976 will have full protection from the 2009 H1N1. People vaccinated in 1976 should still be given the 2009 H1N1 vaccine. Can people who are allergic to eggs receive the 2009 H1N1 flu vaccine?
- 88. People who are allergic to eggs might be at risk for allergic reactions from receiving influenza vaccines, including the 2009 H1N1 vaccine. People who have had any of the following symptoms or experiences should consult with a doctor or other medical professional before considering any influenza vaccination: hives or swelling of the lips or tongue acute respiratory distress (trouble breathing) after eating eggs documented hypersensitivity to eggs, including those who have had asthma related to egg exposure at their workplace or other allergic responses to egg protein Because children with severe asthma are at high risk of serious complications from influenza, a regimen has been developed for giving influenza vaccine to children with severe asthma and egg hypersensitivity. Supply and Distribution How do project areas know how much vaccine is available for them to order? CDC sends project areas a weekly 2009 H1N1 allocation report each morning as it does for seasonal influenza vaccine. The report indicates how much of each formulation of 2009 H1N1 vaccine is available for them to order. What is the number of doses “allocated” for ordering? The number of doses "allocated" for ordering is the amount that is at the distribution depots and ready for states to order. The quantity of vaccine allocated is based on the project area's population size. As an example, if 6 million doses total (3 million doses of nasal spray vaccine AND 3 million doses of injectable vaccine) are ready for ordering nationally (as of today) and a state has 10% of the US population, then their allocation for today is 600,000 doses total (300,000 doses of the nasal spray vaccine and 300,000 doses of injectable vaccine). How is vaccine shipped to project areas? CDC’s contractor for centralized distribution ships vaccine to hospitals, clinics, doctor’s offices, health departments, and other providers of vaccines that have been designated as vaccine-receiving sites by the Project Area (the project areas include all 50 states, the District of Columbia, 8 US Territories and freely associated states, and 3 large metropolitan health departments). What kind of providers can be designated as vaccine recipients? Providers that have the capability to receive, store and administer vaccine, including but not limited to provider offices, occupational health clinics, hospitals, local health departments, community vaccinators and pharmacies. How many sites can a jurisdiction designate to receive vaccine? There is a maximum of 150,000 sites to which vaccine can be shipped via centralized distribution. Project areas have received information about their allocation of sites. What should project areas expect with respect to frequency of vaccine shipments? Vaccine will be shipped as it becomes available, taking into account state allocations and orders. The process is modeled after that utilized by immunization programs to order seasonal influenza vaccine off the federal contract. Details about CDC's ordering/allocation process for seasonal influenza are described in the all-grantee message sent to immunization program grantees on 8/11/2009 (Grantee message for allocation). What is the minimum dose order for shipments of 2009 H1N1 vaccine? For each vaccine formulation (identified by its National Drug Code) the minimum dose order is 100 doses and all orders must be placed in increments of 100 doses. Each ancillary supply kit contains supplies to support 100 doses of vaccine, with different kits available for prefilled syringe products and for multi-dose vial products. When and how much of the 2009 H1N1 vaccine will be available? Both the flu shot (in the arm) and nasal spray form of 2009 H1N1 vaccines have now been produced and licensed by the Food and Drug Administration. The 2009 H1N1 vaccine first became available in early October and more doses are becoming available every week. Vaccine availability, however, depends on many factors so these numbers will
- 89. be frequently updated. The first doses of live attenuated 2009 H1N1 flu vaccine were administered on October 5, 2009. Administration of the 2009 H1N1 flu shot began the week of October 12. Where will the vaccine be available? Every state is developing a vaccine delivery plan. Vaccine will be available in a combination of settings such as vaccination clinics organized by local health departments, healthcare provider offices, schools, and other private settings, such as pharmacies and workplaces. For more information, see State/Jurisdiction Contact Information for Health Care Providers Interested in Providing H1N1 Vaccine. For information on seasonal vaccine supply and distribution, visit Seasonal Influenza Vaccine Supply for the U.S. 2009-2010 Influenza Season. Seasonal and H1N1 Vaccine Does the seasonal flu vaccine also protect against the 2009 H1N1 flu? The seasonal flu vaccine will not protect you against 2009 H1N1 flu. For more information about the seasonal flu vaccine, read Key Facts About Seasonal Flu Vaccine. Is this vaccine made differently than the seasonal influenza vaccine? No. This vaccine will be made using the same processes and facilities that are used to make the currently licensed seasonal influenza vaccines. Can the seasonal vaccine and the 2009 H1N1 vaccine be given at the same time? Inactivated 2009 H1N1 vaccine can be administered at the same visit as any other vaccine, including pneumococcal polysaccharide vaccine. Live 2009 H1N1 vaccine can be administered at the same visit as any other live or inactivated vaccine EXCEPT seasonal live attenuated influenza vaccine. Prior Illness Should I get vaccinated against 2009 H1N1 if I have had flu-like illness since the Spring of 2009? The symptoms of influenza (flu-like illnesses) are similar to those caused by many other viruses. Even when influenza viruses are causing large numbers of people to get sick, other viruses are also causing illnesses. Specific testing, called “RT-PCR test,” is needed in order to tell if an illness is caused by a specific influenza strain or by some other virus. This test is different from rapid flu tests that doctors can do in their offices. Since most people with flu-like illnesses will not be tested with RT-PCR this season, the majority will not know whether they have been infected with 2009 H1N1 flu or a different virus. Therefore, if you were ill but do not know if you had 2009 H1N1 infection, you should get vaccinated, if your doctor recommends it. So, most people recommended for 2009 H1N1 vaccination should be vaccinated with the 2009 H1N1 vaccine regardless of whether they had a flu-like illness earlier in the year. If you have had 2009 H1N1 flu, as confirmed by an RT-PCR test, you should have some immunity against 2009 H1N1 flu and can choose not to get the 2009 H1N1 vaccine. However, vaccination of a person with some existing immunity to the 2009 H1N1 virus will not be harmful. For more information on flu tests, see Influenza Diagnostic Testing During the 2009-2010 Flu Season. Any immunity from 2009 H1N1 influenza infection or vaccination will not provide protection against seasonal influenza. All people who want protection from seasonal flu should still get their seasonal influenza vaccine. Prevention Are there other ways to prevent the spread of illness? Take everyday actions to stay healthy.
- 90. Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it. Wash your hands often with soap and water, especially after you cough or sneeze. If soap and water are not available, use an alcohol-based hand rub.* Avoid touching your eyes, nose or mouth. Germs spread that way. Stay home if you get sick. CDC recommends that you stay home from work or school and limit contact with others to keep from infecting them. Follow public health advice regarding school closures, avoiding crowds and other social distancing measures. These measures will continue to be important after a 2009 H1N1 vaccine is available because they can prevent the spread of other viruses that cause respiratory infections. What about the use of antivirals to treat 2009 H1N1 infection? CDC has issued interim guidance for the use of antiviral drugs for this season. CDC also has published Questions & Answers related to the use of antiviral drugs for this season. Are natural remedies (also referred to as “complementary” or “alternative” medicine) recommended to prevent the 2009 H1N1 flu virus? The first and most important step to prevent the flu is to get vaccinated. Vaccination stimulates an immune response using a killed or weakened virus that uses the body’s own defense mechanisms to prevent infection. CDC's current recommendations to protect against 2009 H1N1 virus do not include natural remedies as a sole prevention method. If you want to use a natural remedy to reduce symptoms, CDC recommends that you talk to your healthcare provider about options. Alternative medicine should not be used as a replacement for proven conventional care, or to postpone seeing a doctor about a medical problem. The National Institutes of Health (NIH) provides information at http://health.nih.gov/topic/AlternativeMedicine on specific alternative options, including scientific information, potential side effects, and cautions for each. The Federal Trade Commission (FTC) warns consumers to be cautious about products that claim to prevent, treat, or cure 2009 H1N1 influenza, specifically products like pills, air filtration devices, and cleaning agents can kill or eliminate the virus. Page last reviewed November 13, 2009, 12:30 PM ET Page last updated November 13, 2009, 12:30 PM ET Content source: Centers for Disease Control and Prevention Centers for Disease Control and Prevention 1600 Clifton Rd. Atlanta, GA 30333, USA 800-CDC-INFO (800-232-4636) TTY: (888) 232-6348, 24 Hours/Every Day - cdcinfo@cdc.gov
- 91. Key Facts About Seasonal Influenza (Flu) What is Influenza (Also Called Flu)? The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent seasonal flu is by getting a seasonal flu vaccination each year. Every year in the United States, on average: 5% to 20% of the population gets the flu; more than 200,000 people are hospitalized from flu-related complications; and about 36,000 people die from flu-related causes. Some people, such as older people, young children, pregnant women and people with certain health conditions (such as asthma, diabetes, or heart disease), are at increased risk for serious complications from seasonal flu illness. This flu season, scientists believe that a new and very different flu virus (called novel 2009 H1N1) may cause a lot more people to get sick than during a regular flu season. It also may cause more hospital stays and deaths than regular seasonal flu. More information about the new H1N1 flu is available here. Symptoms of Flu Symptoms of seasonal flu include: fever (often high) headache extreme tiredness dry cough sore throat runny or stuffy nose muscle aches Stomach symptoms, such as nausea, vomiting, and diarrhea, also can occur but are more common in children than adults. Some people who have been infected with the new H1N1 flu virus have reported diarrhea and vomiting. Complications of Flu Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. How Flu Spreads Flu viruses are thought to spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5-7 days after becoming sick. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Preventing Seasonal Flu: Get Vaccinated The single best way to prevent seasonal flu is to get a seasonal flu vaccination each year. There are two types of flu vaccines: The "flu shot" – an inactivated vaccine (containing killed virus) that is given with a A seasonal flu vaccine needle. The seasonal flu shot is approved for use in people 6 months of age and older, will not protect you including healthy people and people with chronic medical conditions. against the new 2009 The nasal-spray flu vaccine – a vaccine made with live, weakened flu viruses that H1N1 flu. A vaccine
- 92. do not cause the flu (sometimes called LAIV for "Live Attenuated Influenza against the new H1N1 Vaccine"). LAIV is approved for use in healthy* people 2-49 years of age who are not pregnant. flu is being produced. About two weeks after vaccination, antibodies develop that protect against influenza virus infection. Flu vaccines will not protect against flu-like illnesses caused by non-influenza viruses. When to Get Vaccinated Against Seasonal Flu Yearly seasonal flu vaccination should begin in September, or as soon as the seasonal flu vaccine is available, and continue throughout the flu season into December, January, and beyond. This is because the timing and duration of flu seasons vary. While seasonal flu outbreaks can happen as early as October, most of the time seasonal flu activity peaks in January or later. Information about when to get vaccinated with the new H1N1 flu vaccine can be found here. Who Should Get Vaccinated Against Seasonal Flu? In general, anyone who wants to reduce their chances of getting seasonal flu can get vaccinated. However, certain people should get vaccinated each year either because they are at high risk of having serious flu-related complications or because they live with or care for high risk persons. During flu seasons when vaccine supplies are limited or delayed, the Advisory Committee on Immunization Practices (ACIP) makes recommendations regarding priority groups for vaccination. People who should get a seasonal flu vaccination each year include: 1. Children aged 6 months up to their 19th birthday 2. Pregnant women 3. People 50 years of age and older 4. People of any age with certain chronic medical conditions 5. People who live in nursing homes and other long-term care facilities 6. People who live with or care for those at high risk for complications from flu, including: a. Health care workers b. Household contacts of persons at high risk for complications from the flu c. household contacts and caregivers of children <5 years of age with particular emphasis on vaccinating contacts of children <6 months of age (these children are at higher risk of flu-related complications) Information about who should get vaccinated against the new 2009 H1N1 flu, including the ACIP recommendations for the new H1N1 flu vaccine can be found here. Use of the Nasal Spray Seasonal Flu Vaccine Vaccination with the nasal-spray flu vaccine is an option for healthy* people 2-49 years of age who are not pregnant, even healthy persons who live with or care for those in a high risk group. The one exception is healthy persons who care for persons with severely weakened immune systems who require a protected environment; these healthy persons should get the inactivated flu vaccine. (A nasal spray vaccine against seasonal flu will not protect you against the new H1N1 flu. A vaccine against the new H1N1 flu is being produced.) Who Should Not Be Vaccinated Against Seasonal Flu Some people should not be vaccinated without first consulting a physician. They include: People who have a severe allergy to chicken eggs. People who have had a severe reaction to an influenza vaccination in the past. People who developed Guillian-Barré syndrome (GBS) within 6 weeks of getting an influenza vaccine previously. Children less than 6 months of age (influenza vaccine is not approved for use in this age group). People who have a moderate or severe illness with a fever should wait to get vaccinated until their symptoms lessen. If you have questions about whether you should get a flu vaccine, consult your health-care provider. For more about preventing the flu, see the following:
- 93. Key Facts About Seasonal Flu Vaccine Influenza Antiviral Drugs Good Health Habits for Prevention The Flu: A Guide for Parents * "Healthy" indicates persons who do not have an underlying medical condition that predisposes them to influenza complications. Page last reviewed: October 16, 2009 Page last updated: October 16, 2009 Content source: Centers for Disease Control and Prevention Centers for Disease Control and Prevention 1600 Clifton Rd. Atlanta, GA 30333, USA 800-CDC-INFO (800-232-4636) TTY: (888) 232-6348, 24 Hours/Every Day - cdcinfo@cdc.gov
- 94. Interim Guidance for Clinicians on the Prevention and Treatment of 2009 H1N1 Influenza Infection in Infants and Children May 13, 2009 3:30 PM ET This document provides interim guidance for clinicians who are caring for young children with 2009 H1N1 Influenza infection. As additional information becomes available, the guidance in this document may be updated. Infants and Children and the 2009 H1N1 Influenza Children, especially those younger than 5 years of age and those who have high risk medical conditions, including those with neuromuscular and neurodevelopmental conditions, are at increased risk for influenza-related complications. Among children less than 5 years, the risk for sever complications from seasonal influenza is highest among children less than 2 years old. Illnesses caused by influenza virus infection are difficult to distinguish from illnesses caused by other respiratory pathogens based on symptoms alone. Young children are less likely to have typical influenza symptoms (e.g., fever and cough) and infants may present to medical care with fever and lethargy, and may not have cough or other respiratory symptoms or signs. Influenza-associated deaths among children, while uncommon, do occur with seasonal influenza with an estimated average of approximately 92 influenza-related pediatric deaths each year in the United States. Some deaths in children have been associated with co-infection with influenza and Staphylococcus aureus, particularly methicillin resistant S. aureus (MRSA). Symptoms of severe disease may include: Apnea Tachypnea Dyspnea Cyanosis Dehydration Altered mental status Extreme irritability Children with Developmental Disabilities, and Chronic Medical Conditions Certain children are at higher risk for complications from influenza infection. An investigation of 153 seasonal influenza-associated deaths among children during the 2003-2004 season found that 33% of the children had an underlying condition recognized to increase the risk of influenza-related complications, and 20% had other chronic conditions; 47% had previously been healthy. Chronic neurologic or neuromuscular conditions were present in one third. Children at higher risk include infants < 6 months and all children with immune suppression, pregnancy, chronic kidney disease, heart disease, HIV/AIDS, diabetes, asthma or other problems of the lungs, sickle cell disease, and those on long-term aspirin therapy for chronic disorders. In addition, children with any condition that affects respiratory function including neurological conditions such as intellectual and developmental disability, cerebral palsy, spinal cord injuries, seizure disorders, metabolic conditions or other neuromuscular disorders have higher risk. Other children with an increased risk for complications are those with poor nutritional and fluid intake because of prolonged vomiting and diarrhea, and children with an underlying metabolic disorder such as medium-chain acyl- CoA dehydrogenase (MCAD) deficiency who are unable to tolerate prolonged periods of fasting. Because many
- 95. children with neurological or metabolic conditions may not have the ability to report onset or worsening of symptoms, delay in identification of influenza infection can lead to additional complications. In addition, in one study among HIV-infected children who were not taking antiretroviral medication, influenza was more severe and hospitalization and bacterial complications were more common than among uninfected (i.e, non-HIV infected) children. Special Considerations for Children Aspirin or aspirin-containing products (e.g. bismuth subsalicylate – Pepto Bismol) should not be administered to any confirmed or suspected ill case of novel influenza H1N1 virus infection aged 18 years old and younger due to the risk of Reye syndrome. For relief of fever, other anti-pyretic medications such as acetaminophen or non- steroidal anti-inflammatory drugs are recommended. Children younger than 4 years of age should not be given over-the-counter cold medications without first speaking with a healthcare provider. Treatment and Chemoprophylaxis of Novel Influenza A (H1N1) Virus with Antivirals This novel influenza A (H1N1) virus is sensitive (susceptible) to the neuraminidase inhibitor antiviral medications, zanamivir and oseltamivir. It is resistant to the adamantane antiviral medications, amantadine and rimantadine. Oseltamivir or zanamivir can be used for the treatment and prophylaxis of novel influenza A (H1N1) virus infection. Consult the current recommendations or the pediatric supplement for antiviral use. Recommendations for use of antivirals may change as data on antiviral effectiveness, side effects and antiviral susceptibilities become available. For current information on the see side effects associated with oseltamivir and zanamivir. Treatment For antiviral treatment of novel influenza A (H1N1) virus infection, either oseltamivir or zanamivir are recommended.Oseltamivir has previously been approved for treatment of children one year of age and older. Oseltamivir treatment of children under one year of age with novel influenza A (H1N1) infection was recently approved under an Emergency Use Authorization (EUA) (see below). Oseltamivir dosage is weight-dependent for children one year of age and older, and age-based for children under one year of age. Zanamivir is approved for treatment of children 7 years of age or older, and is an inhaled medication. Treatment with zanamivir or oseltamivir should be initiated as soon as possible after the onset of symptoms. Evidence for benefits from treatment in studies of seasonal influenza is strongest when treatment is started within 48 hours of illness onset. However, some studies of treatment of seasonal influenza have indicated benefit, including reductions in mortality or duration of hospitalization even for patients whose treatment was started more than 48 hours after illness onset. Recommended duration of treatment is five days. Children Under 1 Year of Age Children less than one year of age are at higher risk for complications associated with seasonal human influenza virus infections compared to older children, and the risk of influenza complications is especially high for children less than 6 months of age. Children less than 1 year old are also known to be at increased risk of complications during previous pandemics. Limited safety data on the use of oseltamivir (or zanamivir) for treatment of seasonal influenza in children less than one year of age suggest that severe adverse events are rare. Oseltamivir use for treatment of children less than 1 year old with novel influenza A (H1N1) infection was recently approved by the FDA under an EUA, and dosing for these children is age-based. See current CDC guidelines for treatment guidance in this age group, including recommendations for who should be prioritized for treatment. For information on the EUA, see Emergency Use Authorization of Tamiflu (oseltamivir). Chemoprophylaxis For antiviral chemoprophylaxis of novel influenza A (H1N1) infection, either oseltamivir or zanamivir is recommended. Oseltamavir is approved for chemoprophylaxis in children 12 months or older. However, oseltamavir can be used for chemoprophylaxis under the EUA for children less than 1 year-old to prevent novel
- 96. influenza A (H1N1) infection. Under this EUA, chemoprophylaxis is not recommended for infants less than 3 months old unless the situation is judged to be critical. For children 12 months or older, the dosage is weight- dependent; for children less than 12 months of age, dosage is age-dependent. Zanamivir is approved for chemoprophylaxis in children 5 years or older. Duration of antiviral chemoprophylaxis post-exposure is 10 days after the last known exposure to an ill confirmed case of novel influenza A (H1N1) virus infection. In limited circumstances, antivirals can be used for pre-exposure protection (see antiviral guidance link), and current guidance should be consulted for details. General Health Prevention Supplies of 2009 H1N1 vaccine are limited but continue to increase. More doses are expected for shipment each week. As this program expands and more vaccine continues to become available, members of the public are asked to be patient. The seasonal influenza vaccine that many children receive each fall or winter should not be expected to provide substantial protection against this novel H1N1 influenza A (H1N1) virus, but studies are underway to see if partial protection might be possible. Parents and caretakers should be reminded of the importance of maintaining their child’s health by making sure their children’s other vaccines are up to date. Parents of children with chronic medical conditions who require medication (e.g., HIV/AIDS) are encouraged to make sure their children continue taking their medications Messages for Pediatrician Clinics Caring for Children This 3.5 minutes message can be used by health care providers to deliver information to their patient's families when they call the office. Includes basic novel H1N1 influenza information, when to seek emergency care, keeping your child healthy, and where to seek additional information. Other Guidance Documents General Caring for a sick patient at home Clinician guidance Antiviral guidance Page last reviewed May 13, 2009 3:30 PM ET Page last updated May 13, 2009 3:30 PM ET Content source: Centers for Disease Control and Prevention Centers for Disease Control and Prevention 1600 Clifton Rd. Atlanta, GA 30333, USA 800-CDC-INFO (800-232-4636) TTY: (888) 232-6348, 24 Hours/Every Day - cdcinfo@cdc.gov
- 97. Welcome Choose a link below Common Lab Values Dales Nursing Place Hematology Values Electrolyte Values Nursing Pages Hepatic Enzymes Renal Related Protein Lipids Thyroid Cardiac Hematology Values HEMATOCRIT (HCT) Normal Adult Female Range: 37 - 47% Optimal Adult Female Reading: 42% Normal Adult Male Range 40 - 54% Optimal Adult Male Reading: 47 Normal Newborn Range: 50 - 62% Optimal Newborn Reading: 56 HEMOGLOBIN (HGB) Normal Adult Female Range: 12 - 16 g/dl Optimal Adult Female Reading: 14 g/dl Normal Adult Male Range: 14 - 18 g/dl Optimal Adult Male Reading: 16 g/dl Normal Newborn Range: 14 - 20 g/dl Optimal Newborn Reading: 17 g/dl MCH (Mean Corpuscular Hemoglobin)
- 98. Normal Adult Range: 27 - 33 pg Optimal Adult Reading: 30 MCV (Mean Corpuscular Volume) Normal Adult Range: 80 - 100 fl Optimal Adult Reading: 90 Higher ranges are found in newborns and infants MCHC (Mean Corpuscular Hemoglobin Concentration) Normal Adult Range: 32 - 36 % Optimal Adult Reading: 34 Higher ranges are found in newborns and infants R.B.C. (Red Blood Cell Count) Normal Adult Female Range: 3.9 - 5.2 mill/mcl Optimal Adult Female Reading: 4.55 Normal Adult Male Range: 4.2 - 5.6 mill/mcl Optimal Adult Male Reading: 4.9 Lower ranges are found in Children, newborns and infants W.B.C. (White Blood Cell Count) Normal Adult Range: 3.8 - 10.8 thous/mcl Optimal Adult Reading: 7.3 Higher ranges are found in children, newborns and infants. PLATELET COUNT Normal Adult Range: 130 - 400 thous/mcl Optimal Adult Reading: 265 Higher ranges are found in children, newborns and infants NEUTROPHILS and NEUTROPHIL COUNT - this is the main defender of the body against infection and antigens. High levels may indicate an active infection. Normal Adult Range: 48 - 73 % Optimal Adult Reading: 60.5 Normal Children’s Range: 30 - 60 % Optimal Children’s Reading: 45
- 99. LYMPHOCYTES and LYMPHOCYTE COUNT - Elevated levels may indicate an active viral infections such as measles, rubella, chickenpox, or infectious mononucleosis. Normal Adult Range: 18 - 48 % Optimal Adult Reading: 33 Normal Children’s Range: 25 - 50 % Optimal Children’s Reading: 37.5 MONOCYTES and MONOCYTE COUNT - Elevated levels are seen in tissue breakdown or chronic infections, carcinomas, leukemia (monocytic) or lymphomas. Normal Adult Range: 0 - 9 % Optimal Adult Reading: 4.5 EOSINOPHILS and EOSINOPHIL COUNT - Elevated levels may indicate an allergic reactions or parasites. Normal Adult Range: 0 - 5 % Optimal Adult Reading: 2.5 BASOPHILS and BASOPHIL COUNT - Basophilic activity is not fully understood but it is known to carry histamine, heparin and serotonin. High levels are found in allergic reactions. Normal Adult Range: 0 - 2 % Optimal Adult Reading: 1 TOP of Page Electrolyte Values SODIUM - Sodium is the most abundant cation in the blood and its chief base. It functions in the body to maintain osmotic pressure, acid-base balance and to transmit nerve impulses. Very Low value: seizure and Neurologic Sx. Normal Adult Range: 135-146 mEq/L Optimal Adult Reading: 140.5 POTASSIUM - Potassium is the major intracellular cation. Very low value: Cardiac arythemia. Normal Range: 3.5 - 5.5 mEq/L Optimal Adult Reading: 4.5
- 100. CHLORIDE - Elevated levels are related to acidosis as well as too much water crossing the cell membrane. Decreased levels with decreased serum albumin may indicate water deficiency crossing the cell membrane (edema). Normal Adult Range: 95-112 mEq/L Optimal Adult Reading: 103 CO2 (Carbon Dioxide) - The CO2 level is related to the respiratory exchange of carbon dioxide in the lungs and is part of the bodies buffering system. Generally when used with the other electrolytes, it is a good indicator of acidosis and alkalinity. Normal Adult Range: 22-32 mEq/L Optimal Adult Reading: 27 Normal Childrens Range - 20 - 28 mEq/L Optimal Childrens Reading: 24 CALCIUM - involved in bone metabolism, protein absorption, fat transfer muscular contraction, transmission of nerve impulses, blood clotting and cardiac function. Regulated by parathyroid. Normal Adult Range: 8.5-10.3 mEq/dl Optimal Adult Reading: 9.4 PHOSPHORUS - Generally inverse with Calcium. Normal Adult Range: 2.5 - 4.5 mEq/dl Optimal Adult Reading: 3.5 Normal Childrens Range: 3 - 6 mEq/dl Optimal Childrens Range: 4.5 ANION GAP (Sodium + Potassium - CO2 + Chloride) - An increased measurement is associated with metabolic acidosis due to the overproduction of acids (a state of alkalinity is in effect). Decreased levels may indicate metabolic alkalosis due to the overproduction of alkaloids (a state of acidosis is in effect). Normal Adult Range: 4 - 14 (calculated) Optimal Adult Reading: 9 CALCIUM/PHOSPHORUS Ratio Normal Adult Range: 2.3 - 3.3 (calculated) Optimal Adult Reading: 2.8 Normal Children’s range: 1.3 - 3.3 (calculated) Optimal Children’s Reading: 2.3
- 101. SODIUM/POTASSIUM Normal Adult Range: 26 - 38 (calculated) Optimal Adult Reading: 32 Top of Page Hepatic Enzymes AST (Serum Glutamic-Oxalocetic Transaminase - SGOT ) - found primarily in the liver, heart, kidney, pancreas, and muscles. Seen in tissue damage, especially heart and live Normal Adult Range: 0 - 42 U/L Optimal Adult Reading: 21 ALT (Serum Glutamic-Pyruvic Transaminase - SGPT) - Decreased SGPT in combination with increased cholesterol levels is seen in cases of a congested liver. We also see increased levels in mononucleosis, alcoholism, liver damage, kidney infection, chemical pollutants or myocardial infarction Normal Adult Range: 0 - 48 U/L Optimal Adult Reading: 24 ALKALINE PHOSPHATASE - Used extensively as a tumor marker it is also present in bone injury, pregnancy, or skeletal growth (elevated readings. Low levels are sometimes found in hypoadrenia, protein deficiency, malnutrition and a number of vitamin deficiencies Normal Adult Range: 20 - 125 U/L Optimal Adult Reading: 72.5 Normal Childrens Range: 40 - 400 U/L Optimal Childrens Reading: 220 GGT (Gamma-Glutamyl Transpeptidase) - Elevated levels may be found in liver disease, alcoholism, bile-duct obstruction, cholangitis, drug abuse, and in some cases excessive magnesium ingestion. Decreased levels can be found in hypothyroidism, hypothalamic malfunction and low levels of magnesium. Normal Adult Female Range: 0 - 45 U/L Optimal Female Reading: 22.5 Normal Adult Male Range: 0 - 65 U/L Optimal Male Reading: 32.5 LDH (Lactic Acid Dehydrogenase) - Increases are usually found in cellular death
- 102. and/or leakage from the cell or in some cases it can be useful in confirming myocardial or pulmonary infarction (only in relation to other tests). Decreased levels of the enzyme may be seen in cases of malnutrition, hypoglycemia, adrenal exhaustion or low tissue or organ activity. Normal Adult Range: 0 - 250 U/L Optimal Adult Reading: 125 BILIRUBIN, TOTAL - Elevated in liver disease, mononucleosis, hemolytic anemia, low levels of exposure to the sun, and toxic effects to some drugs, decreased levels are seen in people with an inefficient liver, excessive fat digestion, and possibly a diet low in nitrogen bearing foods Normal Adult Range 0 - 1.3 mg/dl Optimal Adult Reading: .65 Top of Page Renal Related B.U.N. (Blood Urea Nitrogen) - Increases can be caused by excessive protein intake, kidney damage, certain drugs, low fluid intake, intestinal bleeding, exercise or heart failure. Decreased levels may be due to a poor diet, malabsorption, liver damage or low nitrogen intake. Normal Adult Range: 7 - 25 mg/dl Optimal Adult Reading: 16 CREATININE - Low levels are sometimes seen in kidney damage, protein starvation, liver disease or pregnancy. Elevated levels are sometimes seen in kidney disease due to the kidneys job of excreting creatinine, muscle degeneration, and some drugs involved in impairment of kidney function. Normal Adult Range: .7 - 1.4 mg/dl Optimal Adult Reading: 1.05 URIC ACID - High levels are noted in gout, infections, kidney disease, alcoholism, high protein diets, and with toxemia in pregnancy. Low levels may be indicative of kidney disease, malabsorption, poor diet, liver damage or an overly acid kidney. Normal Adult Female Range: 2.5 - 7.5 mg/dl Optimal Adult Female Reading: 5.0 Normal Adult Male Range: 3.5 - 7.5 mg/dl Optimal Adult Male Reading:5.5 BUN/CREATININE - This calculation is a good measurement of kidney and liver function.
- 103. Normal Adult Range: 6 -25 (calculated) Optimal Adult Reading: 15.5 Top of Page Protein PROTEIN, TOTAL - Decreased levels may be due to poor nutrition, liver disease, malabsorption, diarrhea, or severe burns. Increased levels are seen in lupus, liver disease, chronic infections, alcoholism, leukemia, tuberculosis amongst many others. Normal Adult Range: 6.0 -8.5 g/dl Optimal Adult Reading: 7.25 ALBUMIN - major constituent of serum protein (usually over 50%). High levels are seen in liver disease(rarely) , shock, dehydration, or multiple myeloma. Lower levels are seen in poor diets, diarrhea, fever, infection, liver disease, inadequate iron intake, third-degree burns and edemas or hypocalcemia Normal Adult Range: 3.2 - 5.0 g/dl Optimal Adult Reading: 4.1 GLOBULIN - Globulins have many diverse functions such as, the carrier of some hormones, lipids, metals, and antibodies(IgA, IgG, IgM, and IgE). Elevated levels are seen with chronic infections, liver disease, rheumatoid arthritis, myelomas, and lupus are present, . Lower levels in immune compromised patients, poor dietary habits, malabsorption and liver or kidney disease. Normal Adult Range: 2.2 - 4.2 g/dl (calculated) Optimal Adult Reading: 3.2 A/G RATIO (Albumin/Globulin Ratio) Normal Adult Range: 0.8 - 2.0 (calculated) Optimal Adult Reading: 1.9 Top of Page Lipids CHOLESTEROL - High density lipoproteins (HDL) is desired as opposed to the low density lipoproteins (LDL), two types of cholesterol. Elevated cholesterol has been seen in artherosclerosis, diabetes, hypothyroidism and pregnancy. Low levels are seen in depression, malnutrition, liver insufficiency, malignancies, anemia and infection.
- 104. Normal Adult Range: 120 - 240 mg/dl Optimal Adult Reading: 180 LDL (Low Density Lipoprotein) - studies correlate the association between high levels of LDL and arterial artherosclerosis Normal Adult Range: 62 - 130 mg/dl Optimal Adult Reading: 81 mg/dl HDL (High Density Lipoprotein) - A high level of HDL is an indication of a healthy metabolic system if there is no sign of liver disease or intoxication. Normal Adult Range: 35 - 135 mg/dl Optimal Adult Reading: +85 mg/dl TRIGLYCERIDES - Increased levels may be present in artherosclerosis, hypothyroidism, liver disease, pancreatitis, myocardial infarction, metabolic disorders, toxemia, and nephrotic syndrome. Decreased levels may be present in chronic obstructive pulmonary disease, brain infarction, hyperthyroidism, malnutrition, and malabsorption. Normal Adult Range: 0 - 200 mg/dl Optimal Adult Reading: 100 CHOLESTEROL/LDL RATIO Normal Adult Range: 1 - 6 Optimal Adult Reading: 3.5 Top of Page Thyroid THYROXINE (T4) - Increased levels are found in hyperthyroidism, acute thyroiditis, and hepatitis. Low levels can be found in Cretinism, hypothyroidism, cirrhosis, malnutrition, and chronic thyroiditis. Normal Adult Range: 4 - 12 ug/dl Optimal Adult Reading: 8 ug/dl T3-UPTAKE - Increased levels are found in hyperthyroidism, severe liver disease, metastatic malignancy, and pulmonary insufficiency. Decreased levels are found in hypothyroidism, normal pregnancy, and hyperestrogenis status. Normal Adult Range: 27 - 47%
- 105. Optimal Adult Reading: 37 % FREE T4 INDEX (T7) Normal Adult Range: 4 - 12 Optimal Adult Reading: 8 THYROID-STIMULATING HORMONE (TSH) - produced by the anterior pituitary gland, causes the release and distribution of stored thyroid hormones. When T4 and T3 are too high, TSH secretion decreases, when T4 and T3 are low, TSH secretion increases. Normal Adult Range: .5 - 6 milU/L AACE (2003) target level: 0.3 to 3.04 Top of Page Cardiac Creatine phosphokinase (CK) - Levels rise 4 to 8 hours after an acute MI, peaking at 16 to 30 hours and returning to baseline within 4 days 25-200 U/L 32-150 U/L CK-MB CK isoenzyme - It begins to increase 6 to 10 hours after an acute MI, peaks in 24 hours, and remains elevated for up to 72 hours. < 12 IU/L if total CK is <400 IU/L <3.5% of total CK if total CK is >400 IU/L (LDH) Lactate dehydrogenase - Total LDH will begin to rise 2 to 5 days after an MI; the elevation can last 10 days. 140-280 U/L LDH-1 and LDH-2 LDH isoenzymes - Compare LDH 1 and LDH 2 levels. Normally, the LDH-1 value will be less than the LDH-2. In the acute MI, however, the LDH 2 remains constant, while LDH 1 rises. When the LDH 1 is higher than LDH 2, the LDH is said to be flipped, which is highly suggestive of an MI. A flipped pattern appears 12-24 hours post MI and persists for 48 hours. LDH-1 18%-33% LDH-2 28%-40%
- 106. SGOT - will begin to rise in 8-12 hours and peak in 18-30 hours 10-42 U/L Myoglobin - early and sensitive diagnosis of myocardial infarction in the emergency department This small heme protein becomes abnormal within 1 to 2 hours of necrosis, peaks in 4-8 hours, and drops to normal in about 12 hours. < 1 Troponin Complex - Peaks in 10-24 hours, begins to fall off after 1-2 weeks. < 0.4 Table of Cardiac markers Serum Markers of Myocardial Injury Detected Peak Falls Myoglobin 1-3 1-8 12-18 12- CK/CK-MB 3-8 24-48 16 MB Isoforms 1-6 4-8 12-48 cTnI: 5-9 Troponin 10- days 3-6 Complex 24 cTnT: 7- 14 days Typical Marker Values during AMI
- 107. Top of Page