Vasospasm in response to repeated subarachnoid hemorrhages in the monkey

✓ This study investigates the relationship between vasospasm and repeated subarachnoid hemorrhages in 18 monkeys. Sixteen received weekly 4 cc injections of autogenous blood into the subfrontal subarachnoid space. The weekly mortality rate for 4 weeks was 6%, 33%, 20%, and 37% respectively. The over-all mortality was 75%. The degree of vasospasm did not correlate with the morbidity and mortality. Vasospasm was limited to the intradural cerebral vessels and was diffuse. It never lasted longer than a few hours, late vasospasm did not occur, and the degree of vasospasm did not alter with repeated occasions of “subarachnoid hemorrhage.” Immediate electrocardiogram abnormalities were related to the height of the cerebrospinal fluid pressure rise following the subarachnoid hemorrhage (injected blood). Pathological examination of the vessels shown to be in spasm was normal. The study suggests that the increased mortality associated with repeated subarachnoid hemorrhage is due to cumulative structural damage rather than a heightened vasospastic response to repeated hemorrhages.