The critical first minutes after subarachnoid hemorrhage.

Six patients were observed during recurrent subarachnoid hemorrhage (SAH). Three each had an open skull and intact dura mater and demonstrated an extreme increase in intracranial pressure (ICP) that developed within 1 minute and then declined over several minutes. Three other patients were investigated with transcranial Doppler sonography before, during, and after recurrent bleeding, and their hemodynamics were studied. There is conclusive evidence that acute spontaneous SAH is often followed by an intracranial circulatory arrest lasting for several minutes and caused by a peak of ICP in the range of mean arterial levels. The mechanisms involved are discussed. There are strong indications that this temporary intracranial circulatory arrest promotes hemostasis, but may constitute a severe ischemic event.