An Experimental Study on the Effect of Reperfusion on Changes of rCBF in Focal Cerebral Ischemia

ABSTRACT

Reperfusion into focal ischemia using a transorbital snare ligature was studied in 20 unanesthetized cats following middle cerebral artery(MCA) occlusion of 1 to 6 hours duration. Changes of a regional cerebral flow(rCBF) were investigated upon with a hydrogen clearance method in the center and periphery of the MCA territory, which were correlated with the size of infarct delineated by a 2% triphenyl tetrazolium chloride solution and with the occurrence of severe brain edema or hemorrhagic infarct. The results were as followings 1) Post-ischemic hyperperfusion was usually found after 1 hour occlusion of MCA followed by 2 hours recirculation. Final rCBF, however, reached pre-occlusion value and little or no infarct was found. 2) In the 2 hours occlusion-reperfusion group, hypoperfusion after reopening of MCA was regularly found in both the center and the periphery of ischemia, which was well contrasted with hyperperfusion in the 1 hour occlusion group and was accompained by evident but mild infarcts. 3) After 4 and 6 hours occlusion, there was usually evident post-ischemic hyperperfusion soon followed by development of severe hypoperfusion and a higher grade of infarct and hemispheric swelling was found. 4) Final hypoperfusion after transient MCA occlusion was observed only after ischemic periods lasting 2 hours or more irrespective of preceding post-ischemic hyperperfusion and was only related to the duration of the occlusion and not to the degree of blood flow disturbance. 5) Spontaneous hyperemia during occlusion was found in 3 of the 5 cats used in each of the 4 and 6 hours occlusion groups, in which there was marked hyperperfusion after reopening of MCA followed by severe hypoperfusion and transtentorial herniation associated with resulting extensive hemorrhagic infarct and marked hemispheric swelling. 6) Hemorrhagic infarcts were found in one cat of the 4 hour-occlusing group and two of the 6 hour-occlusion group, all of whom showed early hyperemia before reperfusion predictable of such a detrimental result. 7) These data indicate that potential hazard for surgical early revascularization in the acute stage of ischemic stroke should be considered in case profound ischemia had already progressed for 4 hours or more and especially when hyperemia during the initial stage of severe ischemia is observed at the center and the periphery of the ischemic area expected.