In conjunction with our studies of experimental vasoconstriction (NIH Research Grant HL22573, "Treatment of Postsurgical Vasoconstriction"), we are searching for ways to combat the ischemia associated with hemorrhagic vasoconstriction. Subarachnoid hemorrhage causes ischemic cerebral deficits in one third of the patients with ruptured intracranial aneurysms. This finding has been traced to severe cerebral vasoconstriction which leads to impaired cerebral perfusion, ischemia, and infraction. Today there is no therapy that will reverse or dilate cerebral vasoconstriction following subarachnoid hemorrhage. The treatment of ischemia itself might be helpful, and methods such as increased blood volume and blood pressure to improve cerebral perfusion have been used as compromise measures, although they are often ineffective. We seek to study whether other methods of enhancement of the oxygenation of blood will prevent ischemic damage in brain region receiving marginal blood flow. Perfluorochemicals (PFC) are stable carbon chains with fluorine substituted at hydrogen positions. PFC binds oxygen and has been used as a substitute for hemoglobin. PFC as a total replacement for blood can keep animals alive for many weeks because of this peculiar physical chemical property. We believe that the addition of PFC to blood will increase extractable oxygen by 20%. In this application we propose to observe the effect of PFC on ischemic brain lesions due to cerebral vasospasm or brain vessel occlusion.