Book reading 報告日期 : 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 Neurophysiology Intracranial pressure Intracranial pressure-volume relationship Cerebral protection Preoperative assessment Anesthesia for neurosurgery Clinical cases

Neuroanatomy

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 PaCO 2 and PaO 2 on CBF Effects of anesthetics

Cerebral Blood Flow Cerebral Blood Flow= 15% Cardiac output CBF: 50 ml/100g/min CPP =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 PaCO 2 and PaO 2 on CBF PaCO 2 PaO 2 CPP ICP Autoregulation mmHg

Effects of CBF CMRO 2 CPP=MAP-ICP (or CVP) PaCO 2 : 於 PaCO 2 : 20~80mmHg 範圍內, ↑ 1mmHg, CBF ↑ 1-2 ml/100g/min PaO 2

Effects of anesthetics Thiopental ＆ Propofol : CBF ↓ CMRO 2 ↓ Ketamine: CMRO 2 ↑; CBF ＆ ICP ↑ N 2 O:CBF ↑ may be CMRO 2 ↑ Opioids : CBF ↓ CMRO 2 ↓ CBFCMRO 2 ICP Thiopental ＆ Propofol ↓↓ Ketamine↑↑↑ N2ON2O↑ Opioids↓↓ (PaCO 2 ) ↑

Intracranial Pressure-Volume Relationship

IICP ICP=5-15mmHg IICP Positional headache Nausea +Vomiting Hypertension + Bradycardia Conscious change Altered patterns of breathing Papilledema

Methods to decrease ICP 1.Cerebrospinal fluid ↓ Ventricular drainage Lumbar drainage Lasix 2.Cerebral blood volume↓ IV anesthetic HyperventilationPaCO 2 ＜ 30mmHg Avoid hypotension ＆ hypertension 3.Increase venous outflow Elevate head Avoid constriction at the neck. Avoid PEEP Avoid airway pressure↑ 4.Cerebral edema ↓ Mannitol ;Craniectomy Resection space Occupying lesions Prevent ischemia

Effect of anesthetic on ICP Intravenous anesthetic: CMRO 2 ↓CBF ↓ICP ↓ Avoid Etomidate (epilepsy history) Opioids: PaCO 2 ↑ Neuromuscular blocking drugs(-) Volatile anesthetic :CBF ↑ CBV ↑ ICP↑ Dose-dependent increase

Cerebral protection Barbiturates Hypothermia

Intracranial Aneurysms Pre-op Neurologic evaluation IICP? Vasospasm? EKG HHH therapy if vasospasm Calcium channel blockers. Inductio n Avoid ↑SBP. Maintain CPP Avoid ischemia HHH: Hypertension, Hypervolemia, Hemodilution

Intracranial Aneurysms Maintenance Opioid plus propofol or volatile anesthetic Mannitol ( g/kg IV) Normal or ↑systemic blood pressure Postoperative Normal to ↑ systemic blood pressure. Early awakening Neurologic assessment HHH therapy HHH: Hypertension,Hypervolemia Hemodilution

Preoperative Assessment Altered level of consciousness Headaches Motor or sensory deficits IICP? Cranial nerve abnormalities Compression of the optic chiasm focal deficits or visual impairment Seizures Steroid/Diuretic/Anti-convulsion drug…etc. CT/MRI for mass lesion. Mid-line shift?

Monitoring Standard monitors,ex:EKG,NIBP,SpO 2 A-Line, CVP(not routinely used) Capnography, GAS NMT (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) ETCO 2 ↓ 、 SpO 2 ↓ 、 PaCO 2 ↑ Arterial hypoxemia 、 Cardiovascular collapse Transesophageal echocardiography Central 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 PaCO 2 :Keep 30 and 35 mmHg

Common clinical cases  Intracranial Aneurysms  Intracranial Masses  Arteriorvenous Malformation (AVM)  Carotid Stenosis

Intracranial Masses Pre-op IICP? Avoid sedatives and opioids CT/MRI Anxiolytics Monitors Supratentorial masses Standard ASA monitors, A-line, Foley catheter Infratentorial masses depend on positioning Induction+Maintenance Avoid increasing ICP Deep anesthesia Skeletal muscle paralysis Nitrous oxide (X) Mannitol (0.25-1g/kg IV)

Arteriorvenous Malformation (AVM) Pre-op Is similar to that for aneurysms. Intra-op ↓Blood loss A-line, IV Hyperventilation Mannitol Resection Embolization Stereotactic Radiosurgery (gamma knife).

Carotid Stenosis -Carotid Endarterectomy (CEA) Pre-op Neurologic 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 clamping Nitrous 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?