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報告日期 :2012-02-23 指導醫師 : 藺瑞安 醫師指導老師 : 戴溫然 老師報告者 : 黃淑宜、李如萍

Chapter 30 CENTRAL NERVOUS SYSTEM DISEASE

Table of contents

Neuroanatomy NeurophysiologyIntracranial pressureIntracranial pressure-volume relationshipCerebral protection Preoperative assessmentAnesthesia for neurosurgeryClinical cases

NeuroanatomyNeuroanatomy

Neuroanatomy

Blood brain barrier disruption Hypertension Trauma Infection Hypoxemia Sever hypercapnia Tumors Seizure

Neurophysiology

Cerebral Blood Flow Effects of CBF Cerebral Metabolic Rate Cerebral Perfusion Pressure

and Autoregulation. Effects of PaCO2 and PaO2 on CBF Effects of anesthetics

Cerebral Blood Flow

Cerebral Blood Flow= 15% Cardiac outputCBF: 50 ml/100g/minCPP =MAP-ICP (or CVP)

Cerebral Metabolic Rate

Body Temperature 37℃

↓ 1 → CMRO℃ 2↓7 %

Cerebral perfusion and Autoregulation

Autoregulation OK CPP: 50~150mmHg

Autoregulation(-) Trauma ； neurosurgery

Hypertension shifts the auto regulatory curve

Right

Effects of PaCO2 and PaO2 on CBF

PaCO2PaO2

CPP

ICP

Autoregulation50-150mmHg

Effects of CBF

CMRO2

CPP=MAP-ICP (or CVP)PaCO2: 於 PaCO2 :20~80mmHg 範圍內 , ↑ 1mmHg, CBF ↑ 1-2 ml/100g/minPaO2

Effects of anesthetics

Thiopental ＆ Propofol : CBF ↓ CMRO2 ↓Ketamine: CMRO2 ↑; CBF ＆ ICP ↑ N2O:CBF ↑ may be CMRO2 ↑Opioids : CBF ↓ CMRO2 ↓

CBF CMRO2 ICP

Thiopental ＆

Propofol

↓ ↓

Ketamine ↑ ↑ ↑

N2O ↑

Opioids ↓ ↓ (PaCO2)↑

Intracranial Pressure-Volume Relationship

IICP

ICP=5-15mmHg

IICPPositional headacheNausea +VomitingHypertension + BradycardiaConscious changeAltered patterns of breathingPapilledema

Methods to decrease ICP

1.Cerebrospinal fluid ↓ Ventricular drainageLumbar drainageLasix

2.Cerebral blood volume↓ IV anestheticHyperventilationPaCO2 ＜ 30mmHgAvoid hypotension ＆ hypertension

3.Increase venous outflowElevate headAvoid constriction at the neck.Avoid PEEP Avoid airway pressure↑

4.Cerebral edema ↓Mannitol ;CraniectomyResection spaceOccupying lesionsPrevent ischemia

Effect of anesthetic on ICP

Intravenous anesthetic: CMRO2↓CBF ↓ICP ↓Avoid Etomidate (epilepsy history)Opioids: PaCO2↑Neuromuscular blocking drugs(-)

Volatile anesthetic :CBF ↑ CBV ↑ ICP↑ Dose-dependent increase

Cerebral protection

Cerebral protection

Barbiturates

Hypothermia

Intracranial Aneurysms

Pre-op Neurologic evaluation

IICP?

Vasospasm?EKGHHH therapy if vasospasm

Calcium channel blockers.

Induction Avoid ↑SBP. Maintain CPP

Avoid ischemia

HHH: Hypertension, Hypervolemia, Hemodilution

Intracranial Aneurysms

MaintenanceOpioid plus propofol or

volatile anesthetic Mannitol (0.25-1 g/kg IV) Normal or ↑systemic

blood pressure

PostoperativeNormal to ↑ systemic

blood pressure.Early awakening

Neurologic assessmentHHH therapy

HHH: Hypertension ,Hypervolemia Hemodilution

Preoperative Assessment

Altered level of consciousnessHeadachesMotor or sensory deficits IICP?Cranial nerve abnormalitiesCompression of the optic chiasm focal deficits or visual impairmentSeizuresSteroid/Diuretic/Anti-convulsion drug…etc.CT/MRI for mass lesion. Mid-line shift?

Monitoring

Standard monitors,ex:EKG,NIBP,SpO2

A-Line, CVP(not routinely used)Capnography, GASNMT (peripheral nerve stimulator)Foley catheter ICP or EVD monitor

Positioning- Supratentorial tumors

Intracranial vascular lesions

→Supine

Positioning-Sitting (I) Posterior fossa or Infratentorial tumors

Posterior cervical spine and the posterior fossa operation.

Decreased blood in the operative field.Provider have a superior accesses to the airway

and improved ventilation.

Venous Air Embolism (I)Increased risk for venous air embolism

Significant elevation of the head

The operative site above the level of the heart

The venous sinuses in the cut edge of bone

or dura may not collapse when transected.

Venous Air Embolism (II)

ETCO2↓ 、 SpO2 ↓ 、 PaCO2 ↑

Arterial hypoxemia 、 Cardiovascular collapse

Transesophageal echocardiographyCentral venous catheter

Induction of Anesthesia

The Goal of induction Avoid Hyper/Hypotension As close as possible to and certainly within 10% of average awake values Avoid Cough Avoid ICP↑or MAP↓→CBF↓ Avoid use of PEEP PaCO2:Keep 30 and 35 mmHg

Common clinical cases

Intracranial Aneurysms Intracranial Masses Arteriorvenous Malformation (AVM)

Carotid Stenosis

Intracranial Masses

Pre-opIICP? Avoid sedatives

and opioidsCT/MRI Anxiolytics

MonitorsSupratentorial masses Standard ASA monitors,

A-line, Foley catheterInfratentorial masses depend on positioning

Induction+MaintenanceInduction+MaintenanceAvoid increasing ICPDeep anesthesia Skeletal muscle paralysis

Nitrous oxide (X)Mannitol (0.25-1g/kg IV)

Arteriorvenous Malformation (AVM)

Pre-opIs similar to that for

aneurysms.

Intra-op↓Blood lossA-line, IVHyperventilationMannitol

Resection

Embolization

Stereotactic Radiosurgery

(gamma knife).

Carotid Stenosis-Carotid Endarterectomy (CEA)

Pre-opNeurologic

examination is indicated to look for preoperative deficits.

Screen for associated CAD.

Anxiolytics may be useful.

Induction+ Maintenance

Avoid increases in mean arterial pressure

Maintain adequate CPP (baseline to 20% above)

during carotid clampingNitrous oxide.(X)

謝謝聆聽 !!

QUESTIONS OF THE DAY

1. What is cerebral autoregulation? Under what circumstances is it altered? What is the impact of intravenous (IV) or inhaled anesthetics on cerebral autoregulation? 2. What are the effects of changes in PaCO 2 or PaO 2 on cerebral blood flow? 3. What are the effects of IV or inhaled anesthetics on cerebral blood flow? 4. What are the manifestations of venous air embolism in a patient undergoing craniotomy under general anesthesia? What is

the appropriate management? 5. During craniotomy for tumor resection, the surgeon notes “brain swelling” in the operative field. What are the initial steps in management? 6. A patient with subarachnoid hemorrhage (SAH) pre-sents for intracranial aneurysm clipping. What complications of SAH may develop in the perioperative period?