Lecture 1 basic concept on neuroanesthesia 2

BASIC CONCEPT ON
NEUROANESTHESIA
ISNACC

Objective
•To understand technique and anesthetic effect to reach
slack brain.
•To understand technique and anesthetic effect to CBF,
ICP, autoregulation, CO2 reactivity, CMRO2.
•To understand perioperative management.
•To understand mechanism of brain protection and how to
give brain protection.

Cotrell J.E. : Anesthesia for
Neurosurgery, 1994
 New diagnostic equipment
 New monitoring equipment
 New anesthetics
 New understanding common drugs for
neuroanesthesia.
Will be improve outcome in patient with intracranial
disorder.

Anesthesiologist target in
neurosurgery
 Control ICP and brain volume.
 Brain protection from ischemia and injury.
 Less bleeding
Nancye Edwards : Principles and Practice of Neuro anaesthesia,
1991

The relation ICP and mortality
in brain injury
Mean ICP (mm Hg) Mortality (%)
0 - 20 19
21 - 40 28
41 - 80 79
Miller JD : Head injury and brain ischemia
implication for therapy
Br. J Anaesth. 57 : 120 - 129 , 1985

Figure: Idealized intracranial pressure volume relationships. From: Shapiro, H.M.
Intracranial hypertension: Therapeutic and anaesthetic considerations.
Anesthesiology 43: 445-471, 1975

Lecture 1 basic concept on neuroanesthesia 2

Autoregulation:
• Keep until 1,5 MAC Sevoflurane
Gupta et al, Br.J.Anaeth,1997
Summors et al, Anesth Analg , 1999.
• Autoregulation loss at 1,5 MAC Isofluran.
Matta et al, Anesth Analg, 1999.
• One of reasoning: effect dilatation Sevo < Iso

Lam JMK et al, J. Neurosurg, 1997
auto regulation + 5/10 Good outcome
auto regulation + 4/10 Good outcome
auto regulation – severe disability 2
death 9
Mild head injury : 9/29 impairment autoregulation

Methods of brain protection
•Basic methods
•Hypothermia - low normothermia
•Pharmacology
Intravenous Anesthetic : pentothal
Inhalation anesthetics: Sevoflurane
Lidocaine
Mannitol, Magnesium
Erythropoietin
Alpha 2 agonists dexmedetomidine

Basic methods
• Control airway, adequate oxygenation, avoidance
hypoxia, hypercapnia (keep normocapnia).
• Hyperventilation only if herniation present.
• Control of BP/Maintenance of CPP normotension or
induce hypertension 10-20%. CPP >70 mmHg.
• Control ICP (CPP = MAP – ICP). Therapy if ICP 20
mmHg.
• Correction of acidosis, electrolyte imbalance,control
plasma glucose concentration

Mortality:
Head injury with :
Hypoxia : 56%
Hypovolemia : 64%
Hypoxia + Hypovolemia : 76%
Without hypoxia+Hypovolemia : 27%
Asean Congress of Anaesthesiologist, Singapore, 1995.

Anesthesia management :
b
 A = Clear airway
 B = Control ventilation, normocapnia at TBI and slight
hypocapnia at brain tumor.
 C = Avoid high increase or decrease of BP, avoid
increase of cerebral venous pressure. normovolemia,
iso-osmoler.
 D = Avoid drugs & anesthesia technique will increase
ICP, give drugs with brain protection effect.
 E = environment (temperature control) target 35
degree C in OR

Airway
•Clear airway at all the operation and anesthesia.
•Non kinking ETT
•hypoxia or hypercarbia dangerous to patient.

Ventilation to reach :
PaO2 : 100 - 200 mmHg
PaCO2 : 25 - 30 mmHg
for brain tumor surgery
PaCO2 : Normocapnia
in brain injury
Avoid PaCO2 < 20 mmHg
Control ventilation

Regulation BP
 Hypotension :
CPP = MAP - ICP
prefer systolic 90 - 100 mmHg (tumor)
Normotension (trauma)
 Hypertension :
- increase CBV, ICP, edema, blood loss.
- during laringoscopy/intubation,
inserting head pin, skin incision, extubation

Mechanical factor which increase
cerebral venous pressure
 Coughing, bucking
 Trendelenburg
 Neck large vein obstruction
 Abdominal pressure
 PEEP
 internal jugular vein / subclavia vein canulation

Preoperative evaluation
 Similar with routine assessment
 Add : - evaluation ICP, side effect therapy
- CT Scan, MRI
 Premedication :
- avoid narcotic
- diazepam 0,15 mg/kg po
- midazolam 0,025 - 0,05 mg/kg im

Intraoperative anesthetics
1. Monitoring
2. Induction of anesthesia
3. Maintenance of anesthesia :
- inhalation anesthetics (Sevoflurane, isoflurane)
- intra venous anesthetics (pentothal)
- brain relaxation
- Fluid management
4. Emergence and immediate postoperative

Monitoring
 Routine monitoring
 ECG, non invasive BP, CVP, invasive BP (artery line),
FiO2, pulse oximetry, temperature, peripheral nerve
stimulator, catheter urine.

Indication for inserting
artery line
 Rapid changes of BP
 Risk of rapid blood loss.
 Hypotension technique
 Pathologic condition
 Need postoperative ventilation.

Indication for CVP monitoring
 Severe blood loss
 Measurement status volume
 Sitting position / fossa posterior surgery
 vasoactive drugs route

ICP Monitoring
 still controversial
 tumor > 3 cm Need ICP monitoring
 Edema

Target induction of anesthesia
 Control of PaCO2
 Control of BP
 Avoid drainage obstruction of cerebral vein
 Adequate oxygenation & ventilation
 Avoid awareness

Induction of anesthesia
 O2 100%
 Fentanyl 1 - 3 ug/kg
 Pentothal 5 mg/kg 2,5 mg/kg
 Lidocaine 1 - 1,5 mg/kg
 Norcuron 0,1 - 0,15 mg/kg
 oropharyngeal airway
 eye ointment; paper tape.

Technique to avoid increase BP
 Deeper anesthesia: Pentothal
 Narcotic : Fentanyl, Sufentanil
 Nitroprusside ?
 Glyseril trinitrat ?
 Lidocaine 1-1,5 mg/kg iv
 Alpha 2 agonist dexmedetomidine

Hypotension during induction of
anesthesia :
 Elevation extremities, not trendelenburg
 Give crystalloid, colloid
 Vasopressor : if under lower limit of autoregulation

Choice of induction agent
Smooth induction more important than really
drugs combination
Pentothal 3 - 4 mg/kg
Fentanyl 3 - 5 ug/kg
Vecuronium 0,1 - 0,15 mg/kg
or Rocuronium 0,6 - 0,8 mg/kg
or Atracurium 0,5 mg/kg

Maintenance of anesthesia
 Less effect to cerebral autoregulation and response to
CO2
 Stable cardiovascular
 Capable to decrease ICP and increase CPP
 One of choice : pentothal, O2 + Sevoflurane, fentanyl,
relaxant.

Choice of inhalation anesthetics
•Inhalation anesthetic should be evaluated effect on ICP
and cerebral vasculature.
•All inhalation anesthetic has cerebral vasodilatation effect,
will increase CBF, CBV and ICP.
•Must be know the effect on cerebral autoregulation,
response to CO2 reactivity and CMRO2, brain protection
effect.

Variable Halothane Enflurane Isoflurane Sevoflurane
BP
Vascular resistance
Cardiac output
Cardiac contraction
CVP
Heart rate
Sensitization of the
heart to epinephrine
↓ ↓
0
↓ ↓
↓
↑
0
↑ ↑ ↑
↓ ↓
↓
↓ ↓
↓ ↓
↑
↑
↑
↓ ↓
↓ ↓
0
0
0
↑ ↑
0?
↓
↓ ↓
0
0
0
0 ↑
0
Cardiovascular effect of volatile inhalation
anesthetics at 1-1,5 MAC
0 = no change (<10%)
↓ = 10-20% decrease
↓ ↓ = 20-40% decrease
↑ =

Anoxia NMDA/AMPA
Protect
Response
Improve
NA+
Improve
ATP
Improve
Ca+
Protect
Response
Thiopental (600 μM) Yes Yes No/Yes
1
Yes Yes
Midazolam (100 μM) Yes - Yes Yes -
Propofol (20 μg/ml) No Yes Yes Yes No
Lidocaine (10 μM) Yes Yes Yes No -
Isoflurane (1,5%) No No No No -
Sevoflurane (4%) Yes Yes Yes Yes -
Etomidate
3 μg/ml No No No - -
30 μg/ml No Yes No - -
Nitrous oxide (50%) No No No No -
1
Worsens ATP after 3.5 minutes of anoxia:
improves ATP after 10 minutes of anoxia.
Effect of Anesthetics on Physiological ResponsesEffect of Anesthetics on Physiological Responses
and Ion and Metabolite Levelsand Ion and Metabolite Levels
Cottrell JE. ESA, 2004,Lisbon

Maintenance of anesthesia :
 First choice : Sevoflurane
 Second choice : Isoflurane
 TOF : 0
 fluid : 2/3 diuresis
 Mannitol : 0,25 - 1 gr/kg
 Lasix : 0,5 - 1 mg/kg

Fluid
 Stable circulation
 To avoid : hypovolemia, hypervolemia, hypoosmoler,
hyperglycaemia
 First choice NaCl 0,9%, avoid RL, no dextrose: 1-1,5
ml/kg/h or 2/3 diuresis.
 Dextrose : only for therapy hypoglycaemia (blood sugar <
60 mg%)

Extubation
 Be carefully : increase of BP, leading to hyperaemia,
edema, increase of ICP.
 Lidocaine 1 - 1,5 mg/kg, alpha 2 agonist
dexmedetomidine.
 End of surgery increase TOF = 1
 Et CO2 normal
 Difficult to make decision criteria when extubation.

Postoperative periode
 Avoid coughing, bucking, stretching, increase BP.
 Neurological evaluation immediately.
 Mostly extubated at OR
 Lidocaine 1,5 mg/kg, dexmedetomidine, vasodilator,
esmolol to avoid increase BP.
 Analgetics : avoid ketorolac

Immediate or delayed recovery?
• Delayed recovery cannot be recommended as a mechanism of
limiting the metabolic and hemodynamic consequences from
emergence after neurosurgery
Bruder N et al, Anesth Analg 1999; 89(3)

• Awake craniotomy have less PONV than GA.
Manninen P et al. J.of Clin Anesth 2002;14(4)
• Fast-track NA including local anesthetic, combined GA and
local anesthetic, GA with SAFE drug.

Advantages Early awakening
• Earlier neurological examination.
• Earlier indications for further investigations.
• Less hypertension, less catecholamine burst.
• Lower cost

Disadvantages early awakening
• Increased risk of hypoxemia, hypercarbia
• Difficult respiratory monitoring during transfer to the ICU.
• Hypothermia?

Condition for early emergence: systemic
homeostasis
•Normothermia (>36o
C).
•Normovolemia, normotension
(70mmHg<MAP<120mmHg)
•Mild hypocapnia (PaCO2 35 mmHg)
•Normoglycemia (glucose 4-8 mmol/l)
•No hypoosmolality (285 ±5mOsm/kg)
•Hematocrit > 25%
•No coagulation disorder

Conditions for early emergence : brain
homeostasis
• Normal CMRO2 and CBF
• Normal ICP at the end of surgery
• Antiepileptic prophylaxis
• Adequate head up position
• Intact cranial nerves for airway protection

Check-list before attempting early
extubation
Adequate pre-operative state of consciousness.
Limited brain injury, no major brain laceration.
No extensive posterior fossa surgery involving
cranial nerves IX-XII
No major AVM resection: risk of malignant post
operative edema,
Normal body temperature and oxygenation,
cardiovascular stability.

Suggested awakening sequence (1)
Prepare awakening (aim: avoid post operative
respiratory depression).
•Discontinue middle or long acting opioid approx
60 min before planned emergence.
•Stop anesthetic administration during skin
closure.
•Let neuromuscular block decrease to 2/4 if
myorelaxation used. Antagonise myorelaxant
before extubation.
•Progressive rise of PaCO2 to normoventilation

Suggested awakening sequence (2)
•Avoid unnecessary painful stimuli: remove
head pins as early as possible, remove packing
—performed adequate suctioning before the
patient is fully awake.
•Treat BP bursts: treat hypertension due to
nociception, goal MAP < 120 mmHg
(dexmedetomidine, lidocaine, beta blocker).
•Transfer to PACU or ICU: O2, continuous
monitoring (ECG,BP, SpO2)

Systemic and cerebral condition
making delayed emergence
systemic cerebral
Hypothermia (<35,5oC)
Hypertension ( SBP > 150
mmHg)
Hypotension-hypovolemia
Hematocrit < 25%
Hypoxia or hypercapnia
Ineffective spontaneous
ventilation
Hypoosmolality (<280 mOsm/kg)
Disorder of coagulation
Residual neuromuscular block
Preoperative altered
consciousness
Large tumor resection with midline
shift
Long lasting surgery (>6 hours)
Intraoperative brain swelling
Injury to cranial nerves (IX,X,XII)
Convulsions during emergence

Summary
1. Avoiding secondary brain injury will decrease
morbidity and mortality.
2. Choice of anesthetics and technique of anesthesia will
improve outcome.
3. knowledge neurophysiology and neuropharmacology
fully help in patient management.

Lecture 1 basic concept on neuroanesthesia 2

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