Inhibitory effect of activated protein C on cerebral vasospasm after subarachnoid hemorrhage in the rabbit.

This study investigated whether activated protein C (APC) improves the cerebral vasospasm in an experimental subarachnoid hemorrhage that was produced by the intracisternal injection of autologous blood. Male rabbits were divided into the following four groups: APC 0.1-and 0.5-mg groups, in which 0.1 and 0.5 mg APC were injected into the cisterna magna, respectively; a placebo group, in which saline was injected instead of APC; and a sham operation group that did not get injections of autologous blood, APC, and saline. On day 2, amount of clot in the basal cistern was significantly (p < 0.01) decreased in the APC 0.5-mg group. Percent diameter of the basilar artery on day 2 to that before injecting the blood was angiographically determined as 97.1 +/- 3.8% in the APC 0.5-mg group, which was significantly (p < 0.001) greater than the corresponding value in the placebo group (74.8 +/- 3.4%). The impaired endothelium-dependent relaxation following subarachnoid hemorrhage was normalized in the APC 0.5-mg group (p < 0.0001). These results suggest that APC would improve cerebral vasospasm following subarachnoid hemorrhage, possibly by decreasing the amount of subarachnoid clot and normalizing the impaired nitric oxide production/release.