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Anesthesia For Intracranial Aneurysms

Anesthesia For Intracranial Aneurysms. Objectives. Understand the incidence and pathophysiology of aneurysms Considerations in management of aneurysms Anesthetic management New considerations in management of intracranial aneurysms. Incidence. 75% of subarachnoid hemorrhages

Lucy
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Anesthesia For Intracranial Aneurysms

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  1. Anesthesia For Intracranial Aneurysms

  2. Objectives • Understand the incidence and pathophysiology of aneurysms • Considerations in management of aneurysms • Anesthetic management • New considerations in management of intracranial aneurysms

  3. Incidence • 75% of subarachnoid hemorrhages • 27,000 American/year • 6-49 per 100,00 year depending on location • Female predominance • Age 40-60

  4. Incidence • Ruptured intracranial aneurysm (IA) • 20% morbidity • 20% mortality • Unruptured IA • 4% morbidity • 0-2% mortality

  5. 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

  6. Circle Of Willis

  7. Classification • Small – less than 12 mm • Large – 12-24 mm • Giant - 24mm

  8. 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

  9. Factors associated with an increased risk of rupture • Hypertension • Pregnancy • Smoking • Heavy drinking • Strenuous activity

  10. IA Grading • GradeCriteriaPerioperative Mortalit • 0 Aneurysm is not ruptured 0-5 • I Asymptomatic, min. headache and sl. nuchal rigidity 0-5 • II Moderate to severe headache, nuchal rigidity, but no neurologic deficit other than cranial nerve palsy 2-10 • III Somnolence, confusion, medium focal deficits 10-15 • IV Stupor, hemiparesis medium or severe, possible early decerebrate rigidity, vegetative disturbances 60-70 • V Deep coma, decerebrate rigidity, moribund appearance 70-100

  11. World Federation of Neurologic Surgeons (WFNS) SAH grade • WFNS grade GCS Score Major focal deficit* • (0 intact aneurysm) - - • 1 15 absent • 2 13-14 absent • 3 13-14 present • 4 7-12 present or absent • 5 3-6 present or absent

  12. Vasospasm • High incidence angiografically • Clinical symptoms • 4 – 11 days post bleed

  13. Vasospasm • Free hemoglobin - activates cascade • Histamine, serotonin, catecholamines, prostaglandins, angiotensin, and free radicals • Blood vessel walls abnormal

  14. Vasospasm • Treatment • Triple H therapy • Calcium channel blocker - nimodipine • Early surgery with aggressive removal of blood

  15. Rebleed • 14-30 % • Peak incidence first few days post bleed and second week post bleed • High risk of rebleed during angiography

  16. Rebleed and Vasospasm

  17. Cardiovascular effects • ECG abnormalities • Very common • Many changes seen • cannon t wave, Q-T prolongation, ST changes • Autonomic surge may in fact cause some subendocardial injury from increase myocardial wall tension

  18. Cardiovascular effects • Cardiac dysfunction does not appear to affect morbidity or mortality (studies from Zaroff and Browers) • Prolonged Q-T with increased incidence of ventricular arrhythmias • PVC’s are seen in 80%

  19. 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. 82:454p-455p, 1999)

  20. Neurologic effects • Hydrocephalous • Seizures • 13% • Vasospasm may be cause • Increased risk of rebleed • Treat and prophylaxis • Headache, visual field changes, motor deficits

  21. 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

  22. Pulmonary Effects • Neurogenic pulmonary edema • 1-2% with SAH • Hyperactivity of the sympathetic nervous system • Pneumonia in 7-12% of hospitalized patients with SAH

  23. Timing of surgery • 0-3 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

  24. Anesthetic Goals • Avoid abrupt changes in BP • Maintain CBF with normal to high blood pressure • Be prepared for disaster

  25. 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

  26. 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

  27. Induction • Thiopental 3-6mg/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

  28. Maintenance • Goals • Cerebral relaxation and protection • Hemodynamic stability • Normovolemai to hypervolemia • Control ICP • … and wake up on a dime

  29. Maintenance • Agents • Inhalational agents, narcotics, oxygen, • N2O controversial • Can increase CBF • Glucose management • Hyperventilation

  30. Fluids • Isotonic or hypertonic solutions • Mannitol • Increase intravascular volume • Effect in 5-15 min. with peak at 30-45 • Careful administration in those with reduced cardiac function

  31. Hypothermia • Moderate hypothermia determined to be protective in some animal studies (33-35 degrees) • Mild hypothermia (35.5) found to improve outcome but not statistically significant • Deep hypothermic arrest for giant aneurysms

  32. Intraoperative hemorrhage • Hypotension to control • 40 -50 mmHG • Temporary clips • Pressure on ipsilateral carotid for anterior circulation

  33. Emergence • Anticipate stimulating events • Keep beta blockers and vasodilators on hand

  34. Extubation • Decision to extubate made by anesthesia provider and surgeon • Higher grade bleeds may need to go to ICU intubated

  35. New management • Endovascular balloon placement • Tirilazad • Antioxidant • Appears to decrease need for HHH therapy in men • No improved outcome

  36. New Management • Vasospasm • Intraventricular SNP used in severe refractory cases, however effects are highly variable

  37. 4 causes of aneurysmal rupture

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