(New recommendation) Medical Measures to Prevent Rebleeding After aSAH Aneurysm rebleeding is associated with very high mortality and poor prognosis for functional recovery in survivors. The risk of rebleeding is maximal in the first 2 to 12 hours, with reported rates of occurrence between 4% and 13.6% within the first 24 hours.127 130 In fact, more than one third of rebleeds occur within 3 hours and nearly half within 6 hours of symptom onset,131 and early rebleeding is associated with worse outcome than later rebleeding.132 Factors associated with aneurysm rebleeding include longer time to aneurysm treatment, worse neurological status on admission, initial loss of consciousness, previous sentinel headaches (severe head- aches lasting 1 hour that do not lead to the diagnosis of aSAH), larger aneurysm size, and possibly systolic blood pressure 160 mm Hg.87,129,130 Genetic factors, although related to the occurrence of intracranial aneurysms, do not appear to be related to an increased incidence of rebleed- ing.133 Early treatment of the ruptured aneurysm can reduce the risk of rebleeding.71 Among patients who present in a delayed manner and during the vasospasm window, delayed obliteration of aneurysm is associated with a higher risk of rebleeding than early obliteration of aneurysm.134 There is general agreement that acute hypertension should be controlled after aSAH and until aneurysm obliteration, but parameters for blood pressure control have not been defined. A variety of titratable medications are available. Nicardipine may give smoother blood pressure control than labetalol135 and sodium nitroprusside,136 although data showing different clinical outcomes are lacking. 