Cerebral hemodynamic and metabolic changes after experimental subarachnoid hemorrhage

Abstract SAH was produced in baboons by injecting 10 ml of arterial blood into the subarachnoid space in the vicinity of the circle of Willis. Measurements were made in acute and chronic preparations 24 to 48 hr after SAH of CBF, arterial and cerebral venous P CO 2 , pH, oxygen content, serotonin content, intracranial pressure and systemic arterial pressure together with EEG and EKG recordings. During and immediately after SAH, CBF and CMR O 2 increased in spite of a decrease in cerebral perfusion pressure and the occurrence of vasospasm in the larger cerebral arteries demonstrated angiographically. Results obtained following subarachnoidal injection of 10 μg of serotonin were similar to those following injection of blood into the subarachnoid space. Twenty-four to 48 hr after the injection of blood into the subarachnoid space, CBF and CMR O 2 decreased and CVR increased. EEG activity became slow. Arterial spasm was still present. Electron microscopic studies revealed perivascular edema with swelling of astrocytes. This edema was believed to compress the small vessels and to reduce CBF.