L 11-Acid and Base-disorders.ppt lecture
- 1. 1 Acid –Base Imbalance Dr. Eman EL Eter
- 2. Acid-Base Imbalances 2 pH< 7.35 acidosis pH > 7.45 alkalosis PCO2= 35-45 mmHg HCO3- = 22-26 mEq/L The body response to acid-base imbalance is called compensation May be complete if brought back within normal limits Partial compensation if range is still outside norms.
- 3. Compensation 3 If underlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation +buffer system. If problem is respiratory, renal mechanisms can bring about metabolic compensation.
- 4. Acidosis 4 Principal effect of acidosis is depression of the CNS through ↓ of synaptic transmission. Generalized weakness Deranged CNS function the greatest threat Severe acidosis causes Disorientation coma death
- 5. Causes of acidosis 5 A. Respiratory causes: - CNS depression (anaesthesia). - Resp. muscle paralysis/ diaphragm paralysis, - Rib fractures, etc.. - Obstructive lung diseases e.g. Emphysema Pulmonary edema. A. Metabolic causes: - Diabetic ketoacidosis. -Severe diarrehea. -Hypoaldosteronism -Acute renal failure
- 6. Alkalosis 6 Alkalosis causes over excitability of the central and peripheral nervous systems. Numbness Lightheadedness It can cause : Nervousness muscle spasms or tetany Convulsions Loss of consciousness Death
- 7. Causes of alkalosis 7 A- Respiratory: Hyperventilation: - High altitude. - Hysterical. - B. Metabolic: - -Severe vomiting. - Excess antacids. - Hyperaldosteronism.
- 8. Respiratory Acidosis 8 Carbonic acid excess caused by blood levels of CO2 above 45 mm Hg.
- 9. Compensation for Respiratory Acidosis 9 Kidneys eliminate hydrogen ion and retain bicarbonate ion. Kidney also generates new bicarbonate.
- 10. 10
- 11. Respiratory Alkalosis 11 Carbonic acid deficit pCO2 less than 35 mm Hg (hypocapnea) Most common acid-base imbalance Primary cause is hyperventilation
- 12. Respiratory Alkalosis 12 Conditions that stimulate respiratory center and wash out CO2 (Hyperventilation): Oxygen deficiency at high altitudes. Anorexia nervosa. Early salicylate intoxication
- 13. Compensation of Respiratory Alkalosis 13 Kidneys conserve hydrogen ion Excrete bicarbonate ion
- 14. 14
- 15. Metabolic Acidosis 15 Bicarbonate deficit - blood concentrations of HCO3- drops below 22mEq/L Causes: Loss of bicarbonate through diarrhea or renal dysfunction Accumulation of acids (lactic acid or ketones) Failure of kidneys to excrete H+
- 16. Compensation for Metabolic Acidosis 16 Increased ventilation Renal excretion of hydrogen ions if possible K+ exchanges with excess H+ in ECF ( H+ into cells, K+ out of cells)
- 17. 17
- 18. Metabolic Alkalosis 18 Bicarbonate excess - concentration in blood is greater than 26 mEq/L Causes: Excess vomiting = loss of stomach acid Excessive use of alkaline drugs Certain diuretics Endocrine disorders: Hyperaldosteronism. Heavy ingestion of antacids Severe dehydration
- 19. Compensation for Metabolic Alkalosis 19 Kidney excretes alkaline urine and retain H+ Respiratory compensation difficult – hypoventilation limited by hypoxia.
- 20. 20
- 21. Diagnosis of Acid-Base Imbalances 21 1. Note whether the pH is low (acidosis) or high (alkalosis) 2. Decide which value, pCO2 or HCO3 - , is outside the normal range and could be the cause of the problem. If the cause is a change in pCO2, the problem is respiratory. If the cause is HCO3 - the problem is metabolic.
- 22. 22 Compensated or uncompensated? If pH is normal (between 7.35-7.45)….Compenstaed If pH is abnormal (<7.35 or >7.45)….uncompenstated. Respiratory or metabolic? If PCO2>45 = Respiratory acidosis If PCO2<35= Respiratory alkalosis If HCO3-< 22= Metabolic acidosis. If HCO3-> 26 = metabolic alkalosis.
- 23. Example: 23 A patient is in intensive care because he suffered a severe myocardial infarction 3 days ago. The lab reports the following values from an arterial blood sample: pH =7.21, PCO2= 42, HCO3- = 12: List the condition: acidosis or alkalosis, metabolic or respiratory, compensated or uncompensated? Answer: Metabolic acidosis, uncompensated
- 24. Practice 24 pH PaCO2 PaHCO3 Com/un Resp/metab Acid/ alkalosis 7.21 32 14 uncompensated metabolic acidosis 7.5 26 21 uncompensated respiratory alkalosis 7.36 54 32 compensated respiratory acidosis 7.38 38 25 Normal 7.44 30 20 compensated respiratory alkalosis 7.52 36 34 uncompensated metabolic alkalosis 7.37 52 30 compensated respiratory acidosis 7.18 68 29 uncompensated Respiratory acidosis