Interrupted Arterial Occlusion Reduces Ischemic Damage in a Focal Cerebral Ischemia Model of Rats

IT IS GENERALLY thought by neurosurgeons that when temporary clipping of a major cerebral vessel is necessary during aneurysm surgery, repeated short periods of cerebral ischemia are safer for the brain than a single long episode. This study was performed to investigate whether repetitive short episodes of cerebral ischemia would alter the resulting brain injury as compared with a single long period of ischemia in a rat model for focal cerebral ischemia. Middle cerebral artery occlusion and reperfusion were performed by the intraluminal thread technique. The experimental design consisted of a single 90-minute occlusion period in the continuous ischemia group versus three 30-minute occlusion periods with 15-minute reperfusion periods in the repetitive group. Local cerebral blood flow was measured by the hydrogen clearance technique. During the ischemic period, local cerebral blood flow values significantly decreased in both the continuous and the repetitive groups. Cerebral blood flow restoration was demonstrated after each episode of reperfusion in both groups. The neurological status scores 2 hours after surgery in the rats subjected to repetitive insults were significantly better compared with those in the rats of the continuous ischemia group. However, the scores on Days 1, 3, and 7 did not show a significantly better difference. The animals were killed 7 days after the induction of ischemia for the measurement of the infarction area under the microscope. The total area of infarction was significantly reduced (4.05 ± 4.56 versus 47.2 ± 37.3 mm2, P < 0.001) by interruption of the ischemic time period. There was no cortical infarction in the repetitive group, and the infarction area in the basal ganglia was also significantly decreased (4.05 ± 4.56 versus 21.3 ± 10.8 mm2, P < 0.001) in the repetitive group. These results suggested that repeated temporary interruption of blood flow during a neurovascular procedure was safer than a single long occlusion period of the same length of time.