Cyclosporine A reduces cerebral vasospasm after subarachnoid hemorrhage in dogs.

The double subarachnoid hemorrhage canine model was used to test the prophylactic value of immunosuppression in the prevention of cerebral vasospasm after subarachnoid hemorrhage. Dogs treated with cyclosporine A following the regimen prescribed for organ transplant procedures in patients showed a significant reduction in the severity of angiographic constriction of cerebral arteries. While basilar artery diameter after double experimental subarachnoid hemorrhage in a series of untreated dogs (n = 34) averaged 65% of baseline diameter, arterial diameter in dogs treated prophylactically (n = 18) with 6 mg/kg/day cyclosporine A and adjunct low-dose steroid averaged 80% of baseline diameter, for a mean reduction in the severity of chronic arterial constriction of 42%. More important than the average effect, however, is the statistical observation that this mean improvement was obtained primarily by a dramatic reduction in the incidence of severe cerebral vasospasm, the situation most likely to account for morbidity and mortality after aneurysmal rupture.