Vasospasm and cerebral blood flow after subarachnoid hemorrhage.

In a cynomolgus monkey model, the effect of subarachnoid hemorrhage on vessel calibre and cerebral blood flow was studied. Arterial calibres were measured angiographically and cerebral blood flow was measured with 133Xenon intra-arterial clearance techniques. Only a poor correlation between large artery calibre and cerebral blood flow was found, indicating that cerebrovascular resistance changes at the microvascular level play a major role in the acute reduction of cerebral blood flow after subarachnoid hemorrhage, when vasospasm is of mild to moderate degree.