Role of platelet function in symptomatic cerebral vasospasm following aneurysmal subarachnoid hemorrhage.

To evaluate the role of platelet function in the pathogenesis of cerebral vasospasm, we compared sequential changes of platelet aggregability and beta-thromboglobulin and thromboxane B2 concentrations in blood samples from the internal jugular and peripheral vein of 13 patients with aneurysmal subarachnoid hemorrhage. Platelet function in blood from the internal jugular vein tended to be enhanced during days 0-1 but recovered to the normal range during days 2-4. After day 5, platelet function showed various patterns depending on the presence of symptomatic vasospasm. In patients without symptomatic vasospasm, sequential changes were relatively minor, with normal or slightly high values. Patients with symptomatic vasospasm already showed high platelet aggregability during the early stage of vasospasm. The concentration of beta-thromboglobulin increased several days after the onset of vasospasm, reaching 80 ng/ml or more in patients with a poor prognosis. Two of the five patients with symptomatic vasospasm showed markedly high concentrations of thromboxane B2 after day 8. These results suggest that vasospasm activates platelets and promotes aggregability and that the resulting increased tendency for thrombus formation may affect the patient's prognosis during the advanced stage.