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

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

- children : midazolam 0,75 mg/kg po

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

BPVascular resistanceCardiac outputCardiac contractionCVPHeart rateSensitization of the heart to epinephrine

0 0

000 0?

000

0 0

Cardiovascular effect of volatile inhalation anesthetics at 1-1,5 MAC

0 = no change (<10%) = 10-20% decrease = 20-40% decrease = increase

Anoxia NMDA/AMPAProtect

ResponseImprove

NA+Improve

ATPImprove

Ca+Protect

Response

Thiopental (600 μM) Yes Yes No/Yes1 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 -

1Worsens ATP after 3.5 minutes of anoxia: improves ATP after 10 minutes of anoxia.

Effect of Anesthetics on Physiological Responses Effect 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 (>36oC).•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 extubationAdequate 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 emergencesystemic cerebralHypothermia (<35,5oC)Hypertension ( SBP > 150 mmHg)Hypotension-hypovolemiaHematocrit < 25%Hypoxia or hypercapniaIneffective spontaneous ventilationHypoosmolality (<280 mOsm/kg)Disorder of coagulationResidual neuromuscular block

Preoperative altered consciousnessLarge tumor resection with midline shiftLong lasting surgery (>6 hours)Intraoperative brain swellingInjury 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.