Diffuse cerebral ischemia in the cat: I. Local blood flow during severe ischemia and recirculation

The effects of severe cerebral ischemia on postischemic brain perfusion were examined in a series of pentobarbital-anesthetized cats. Ischemia of 15 or 30 min duration was produced by occlusion of both common carotid arteries and the basilar artery and was coupled with mild systemic hypotension. A 90-min period of normotensive postischemic recirculation was permitted in some animals. In 9 of 10 animals studied at the end of ischemic insult and not allowed to recover, blood flow in the cerebral hemispheres was greatly reduced, with minimal flow (0.01 to 0.11 ml gm^-1 min^-1) persisting only in scattered perisulcal regions in 4 animals. Following 15 min of ischemia, blood flow was restored uniformly during recirculation, though at subnormal levels (31 to 35% of control). In contrast, 30 min of prior ischemia led to marked heterogeneities of local cerebral perfusion during recirculation, with multiple zones of persistent severe ischemia. Thus, while recirculation was suboptimal following both 15 and 30 min of ischemia, the 30-min insult led to focal postischemic perfusion abnormalities that were sufficiently severe to make the possibility of functional recovery appear unlikely.