Early effects of experimental arterial subarachnoid haemorrhage on the cerebral circulation. Part II: Regional cerebral blood flow and cerebral microcirculation after experimental subarachnoid haemorrhage.

Employing the experimental set-up and the methods described - in part I of the paper, the measurements of the regional cerebral blood flow (rCBF) and evaluation of brain microcirculation were performed. The control series provided normal values and constituted the reference for the results of the post-haemorrhagic measurements. Arterial subarachnoid haemorrhage increases transitorily the intracranial pressure to values close to the diastolic blood pressure. The rise of the blood pressure (Cushing response) is not adequate to prevent the reduction in the cerebral perfusion pressure. Cerebral blood flow diminishes after arterial subarachnoid haemorrhage during the elevation of intracranial pressure. It results in numerous, disseminated areas of reduced regional cerebral blood flow. During 4 hours following arterial subarachnoid haemorrhage global cerebral blood flow returns to normal values, while focal reductions in blood flow persist in the grey matter structures of both hemispheres. These foci are accompanied by confined areas of markedly increased regional cerebral blood flow. Disseminated foci with a reduced number of patent capillaries are found in the grey matter structures of both hemispheres 1 and 4 hours following arterial subarachnoid haemorrhage. Their number decreases during the 4 hours observation.