Cerebral vasospasm in a double-injection model in rabbit.

The present study was designed to assess the occurrence of cerebral vasospasm following an experimental subarachnoid hemorrhage model in rabbits. Sixty-nine New Zealand albino rabbits were used in this study. One milliliter of fresh arterial blood was injected through the surgically exposed atlanto-occipital membrane over a period of 20 seconds. The procedure was then repeated 24 hours later. Fifty animals underwent digital subtraction angiography at one of the following prefixed intervals: 1, 3, or 8 days after the second injection hemorrhage. Nineteen animals underwent one angiographic examination prior to the instillation of the intracisternal blood. This procedure was followed by a repeated angiography 3 days after the second experimental subarachnoid hemorrhage. For the purpose of evaluation, the films were magnified 10-fold and the diameter of the basilar artery as well as that of the extracranial vertebral artery at three different levels were measured. We assessed the diameter of the basilar artery as well as the mean ratio extracranial vertebral artery/basilar artery diameters. This ratio was considered to minimize anatomical and technical variabilities. The results in the first 50 animals showed a trend suggesting that spasmogenic activity reaches a peak at about the third day after subarachnoid hemorrhage. These results were confirmed in the latter 19 animals. However, mortality in this group was high: 50%. This double-injection model of subarachnoid hemorrhage in rabbits consistently reproduced cerebral vascular spasm 3 days after repeated subarachnoid hemorrhage. However, its usefulness as an experimental model for subarachnoid hemorrhage is limited practically by the high animal mortality in the protocols where repeated angiographic studies are necessary.