Aneurysmal Subarachnoid Hemorrhage

Abstract

Aneurysmal subarachnoid hemorrhage (SAH) is a worldwide health burden with high fatality and permanent disability rates. The overall prognosis depends on the volume of the initial bleed, rebleeding, and degree of delayed cerebral ischemia (DCI). Cardiac manifestations and neurogenic pulmonary edema indicate the severity of SAH. The International Subarachnoid Aneurysm Trial (ISAT) reported a favorable neurological outcome with the endovascular coiling procedure compared with surgical clipping at the end of 1 year. The ISAT trial recruits were primarily neurologically good grade patients with smaller anterior circulation aneurysms, and therefore the results cannot be reliably extrapolated to larger aneurysms, posterior circulation aneurysms, patients presenting with complex aneurysm morphology, and poor neurological grades. The role of hypothermia is not proven to be neuroprotective according to a large randomized controlled trial, Intraoperative Hypothermia for Aneurysms Surgery Trial (IHAST II), which recruited patients with good neurological grades. Patients in this trial were subjected to slow cooling and inadequate cooling time and were rewarmed rapidly. This methodology would have reduced the beneficial effects of hypothermia. Adenosine is found to be beneficial for transient induced hypotension in 2 retrospective analyses, without increasing the risk for cardiac and neurological morbidity. The neurological benefit of pharmacological neuroprotection and neuromonitoring is not proven in patients undergoing clipping of aneurysms. DCI is an important cause of morbidity and mortality following SAH, and the pathophysiology is likely multifactorial and not yet understood. At present, oral nimodipine has an established role in the management of DCI, along with maintenance of euvolemia and induced hypertension. Following SAH, hypernatremia, although less common than hyponatremia, is a predictor of poor neurological outcome.Key Words: subarachnoid hemorrhage, intracranial aneurysm, delayed cerebral ischemia (J Neurosurg Anesthesiol 2015;27:222-240) SUBARACHNOID HEMORRHAGE (SAH) IS A WORLDWIDE HEALTH BURDEN WITH HIGH RATES OF FATALITY AND PERMANENT DISABILITYThe estimated worldwide incidence of SAH is 9/ 100,000 persons/y with regional variation. 1 One systematic review found the incidence to be lower in South and Central America (4.2/100,000 persons/y) and higher in Japan (22.7/100,000 persons/y) and Finland (19.7/100,000 persons/y). 1 Interestingly, the prevalence of intracranial aneurysm is not found to be higher in Japan or Finland, 2 but the risk for rupture is higher. 3 The incidence is also reported lower in China (2.0 //100,000 persons/y). 4 SAH accounts for only 5% of all strokes, 5 but it has high mortality and permanent disability rates. A retrospective cohort study in 2 large Norwegian populations between 1984 and 2007 reported a 30-day case fatality rate of 36%. 6 A nationwide Danish study reported a similar 30-day mortality at 38%. 7 World Health Organization Multinational Monitoring Trends...