THE EFFECT OF SURGERY ON THE SEVERITY OF VASOSPASM

Intracranial aneurysm surgery performed between 4 and 12 days after su barachnoid hemorrhage (SAH) has been associated with an increased risk of delayed cerebral ischemia and poor outcome compared to surgery per formed before or after this time. To investigate whether this increase d risk is due to aggravation of vasospasm, the angiograms obtained bef ore and after surgery in 56 patients operated on at various times afte r aneurysmal SAH were studied. Vasospasm was quantitated by measuring the diameters of intracranial arteries and expressed as the ratio of t he diameters of the intracranial arteries to the diameter of the extra cranial internal carotid artery. Aggressive surgical clot removal was not performed at surgery. To correct for differences in prognostic fac tors for vasospasm between patients operated on at different times aft er SAH, multiple regression analysis was performed using the arterial diameter ratio during vasospasm as the dependent variable and the prog nostic factors for vasospasm, including the time of surgery, as indepe ndent variables. Equations predicting the severity of vasospasm could be generated using the clinical grade on admission, patient age, and p reoperative arterial diameter ratio. The time of surgery had no effect on vasospasm. Cerebral infarction due to vasospasm developed in five (15%) of 34 patients operated on within 3 days after SAH and in four ( 20%) of 20 operated on between 4 and 12 days after SAH (p = 0.66). A g ood outcome for these two groups was achieved in 88% and 85%, respecti vely (p = 1.00). These results suggest that the timing of surgery does not affect the development of vasospasm. Any increased risk of cerebr al ischemia associated with surgery performed between 4 and 12 days af ter SAH is due to factors other than aggravation of vasospasm.