Blood component induction of cerebral vasospasm.

The role of blood components in cerebral vasospasm was evaluated using an in vivo canine model. An intracisternal injection of 5 ml of washed red blood cells (RBCs) and platelet-rich plasma (PRP) resulted in acute vasospasm of the basilar artery as seen by angiography. This was comparable with the degree of vasospasm induced by an injection of the same amount of whole blood. Repeated injections of blood components or whole blood on Days 1 and 3 induced chronic vasospasm, as shown by angiography on Day 7. Results clearly indicate that chronic vasospasm was produced by RBCs and PRP, and it was in a dose-dependent manner with increasing concentrations of RBCs (hematocrit: 30, 50, and 70%). The vasospasm induced by both components closely reproduced that seen with whole blood. Neither acute nor chronic vasospasm induced by blood component injection was associated with clot formation in the subarachnoid space, as confirmed by an autopsy. These results suggest that the extravasation of RBCs and PRP into the subarachnoid space produces cerebral vasospasm by mechanisms independent of blood clot formation.