intracranialAneurysm - Anesthesia For Intracranial...

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Unformatted text preview: Anesthesia For Intracranial Aneurysms Objectives Objectives Understand the incidence and pathophysiology of aneurysms Considerations in management of aneurysms Anesthetic management New considerations in management of intracranial aneurysms Incidence Incidence 75% of subarachnoid hemorrhages 27,000 American/year 6­49 per 100,00 year depending on location Female predominance Age 40­60 Incidence Incidence Ruptured intracranial aneurysm (IA) 20% morbidity 20% mortality Unruptured IA 4% morbidity 0­2% mortality Pathophysiology Pathophysiology Arterial wall abnormalities Saccular, occur at bifurcations Disease processes associated with an increased risk of IA Polycystic kidney Erloh Danlos Fibromuscular disease Coarctation of the aorta Circle Of Willis Circle Of Willis Classification Classification Small – less than 12 mm Large – 12­24 mm Giant ­ 24mm IA Rupture Increase ICP ICP greater than DBP Bleeding stops with decreased CBF Decreased consciousness 2 clinical scenarios typical 1. Return to normal ICP and CBF with return of function 2. High ICP continues with low CBF Factors associated with an increased Factors associated with an increased risk of rupture Hypertension Pregnancy Smoking Heavy drinking Strenuous activity IA Grading IA Grading Grade Perioperative Mortalit 0 Aneurysm is not ruptured 0­5 I Asymptomatic, min. headache and sl. nuchal rigidity 0­5 II Moderate to severe headache, nuchal rigidity, but no neurologic deficit other than cranial nerve palsy 2­10 III Somnolence, confusion, medium focal deficits 10­15 IV Stupor, hemiparesis medium or severe, possible early decerebrate rigidity, vegetative disturbances 60­70 V Deep coma, decerebrate rigidity, moribund appearance 70­100 Criteria World Federation of Neurologic World Federation of Neurologic Surgeons (WFNS) SAH grade WFNS grade GCS Score deficit* Major focal (0 intact aneurysm) 1 15 ­ ­ absent 2 3 13­14 13­14 absent present 4 5 7­12 3­6 present or absent present or absent Vasospasm Vasospasm High incidence angiografically Clinical symptoms 4 – 11 days post bleed Vasospasm Vasospasm Free hemoglobin ­ activates cascade Histamine, serotonin, catecholamines, prostaglandins, angiotensin, and free radicals Blood vessel walls abnormal Vasospasm Vasospasm Treatment Triple H therapy Calcium channel blocker ­ nimodipine Early surgery with aggressive removal of blood Rebleed Rebleed 14­30 % Peak incidence first few days post bleed and second week post bleed High risk of rebleed during angiography Rebleed and Vasospasm Rebleed and Vasospasm Cardiovascular effects Cardiovascular effects ECG abnormalities Very common Many changes seen cannon t wave, Q­T prolongation, ST changes Autonomic surge may in fact cause some subendocardial injury from increase myocardial wall tension Cardiovascular effects Cardiovascular effects Cardiac dysfunction does not appear to affect morbidity or mortality (studies from Zaroff and Browers) Prolonged Q­T with increased incidence of ventricular arrhythmias PVC’s are seen in 80% QTdc QTdc Difference between the longest and shortest QT interval on a 12 lead Increase reported to be associated with cardiorespiratory compromise and need for inotropes (Br. J Anesth. 82:454p­455p, 1999) Neurologic effects Neurologic effects Hydrocephalous Seizures 13% Vasospasm may be cause Increased risk of rebleed Treat and prophylaxis Headache, visual field changes, motor deficits Endocrine Effects Endocrine Effects SIADH Cerebral salt wasting syndrome release of naturetic peptide hypovolemia, increased urine NA and volume contraction Distinguish between the two and treat accordingly Pulmonary Effects Pulmonary Effects Neurogenic pulmonary edema 1­2% with SAH Hyperactivity of the sympathetic nervous system Pneumonia in 7­12% of hospitalized patients with SAH Timing of surgery Timing of surgery 0­3 days post bleed appears to be optimal Improved outcome within 6 hours of rupture despite high H/H grade If delayed, 2 weeks post bleed after fibrinolytic phase Anesthetic Goals Anesthetic Goals Avoid abrupt changes in BP Maintain CBF with normal to high blood pressure Be prepared for disaster Monitors Monitors Arterial line preinduction CVP as indicated Triple H therapy may be used post op Neurologic monitoring SSEPs and BAERs useful for posterior circulation aneurysm Induction Induction REBLEEDING IS LETHAL!!! Careful blood pressure control Weigh risk of full stomach vs. adequate depth of anesthesia and relaxation Titrate induction agent Blunt response to intubation Induction Induction Thiopental 3­6mg/kg reduces CBF and O2 consumption but does not blunt hemodynamic response. Need supplemental agents Propofol and etomidate good alternates Succinylcholine controversy …. Beta blockers and vasodilators on hand Maintenance Maintenance Goals Cerebral relaxation and protection Hemodynamic stability Normovolemai to hypervolemia Control ICP … and wake up on a dime Maintenance Maintenance Agents Inhalational agents, narcotics, oxygen, N2O controversial Can increase CBF Glucose management Hyperventilation Fluids Fluids Isotonic or hypertonic solutions Mannitol Increase intravascular volume Effect in 5­15 min. with peak at 30­45 Careful administration in those with reduced cardiac function Hypothermia Hypothermia Moderate hypothermia determined to be protective in some animal studies (33­35 degrees) Mild hypothermia (35.5) found to improve outcome but not statistically significant Deep hypothermic arrest for giant aneurysms Intraoperative hemorrhage Intraoperative hemorrhage • • • • Hypotension to control 40 ­50 mmHG Temporary clips Pressure on ipsilateral carotid for anterior circulation Emergence Emergence Anticipate stimulating events Keep beta blockers and vasodilators on hand Extubation Extubation Decision to extubate made by anesthesia provider and surgeon Higher grade bleeds may need to go to ICU intubated New management New management Endovascular balloon placement Tirilazad Antioxidant Appears to decrease need for HHH therapy in men No improved outcome New Management New Management Vasospasm Intraventricular SNP used in severe refractory cases, however effects are highly variable 4 causes of aneurysmal rupture 4 causes of aneurysmal rupture ...
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