Anesthesia For Intracranial Aneurysms

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