TEMPORARY VESSEL OCCLUSION IN SPONTANEOUSLY HYPERTENSIVE AND NORMOTENSIVE RATS - EFFECT OF SINGLE AND MULTIPLE EPISODES ON TISSUE METABOLISM AND VOLUME OF INFARCTION

Temporary occlusion of an intracranial artery is frequently necessary in the surgical management of intracranial aneurysms, arteriovenous ma lformations, and tumors. While the risks of vessel damage associated w ith clip application have been lessened by improved design, the threat of ischemic damage remains. It is unclear whether multiple, brief per iods of clip application are more or less safe than a single period of occlusion, and whether the underlying cerebrovascular status influenc es the outcome from either method. The effect of each of these paradig ms (single: 1-hour occlusion; multiple: three 20-minute episodes separ ated by 10 minutes of reperfusion) on histopathological outcome was as sessed in a middle cerebral artery (MCA) occlusion model using both no rmotensive and spontaneously hypertensive rats. The mean volume of inf arction (+/- standard error of the mean) was not different between the single-ischemic (49.4 +/- 17.3 cu mm) and the multiple-ischemic (42.9 +/- 12.9 cu mm) episode groups of normotensive rats, whereas in the s pontaneously hypertensive rats a significant difference existed betwee n the volume of infarction for the single-occlusion group (126.7 +/- 1 8.7 cu mm) and the multiple-occlusion group (162.4 +/- 15.5 cu mm) (p < 0.05). The metabolic data obtained from spontaneously hypertensive a nimals did not provide an explanation for the larger infarction in tha t there were no significant differences between the single- and multip le-occlusion groups with respect to tissue glucose, adenosine triphosp hate, or lactate levels. The results suggest that intermittent reperfu sion may have different effects depending not only on the degree and d uration of ischemia and reperfusion, but also on the underlying cerebr ovascular status.