Reversibility of Experimental Cerebrovascular Obstruction Induced by Complete Ischemia

B Y perfusing rabbit brains with a suspension of carbon, it has been possible to demonstrate the development of vascular obstructions during complete ischemia. These are manifested as white areas in which the perfused carbon fails to displace entrapped red blood cells from portions of the microvasculature. 6 The occlusive changes first appear after 5 to 7.5 minutes of ischemia and increase with time, about half the brain failing to reperfuse after 15 minutes and 60% after 30 minutes of ischemia. Light and electronmicroscopy have demonstrated that the obstruction is due to compression of vascular lumen by swollen endothelial cells and perivascular glia; 4,8 and the protection against the vascular obstruction provided by prior administration of hypertonic Mannitol or glucose 2 is consistent with this interpretation. In some of the prior studies, carbon perfusion was performed immediately after the ischemia; in others, 30 minutes later. The results in the latter group were not appreciably different from the former, 1 but no measures were taken to maintain normal blood pressure during the 30-minute post-ischemia period. Without such measures, marked and persistent hypotension is a regular sequela when cerebral ischemia lasts more than 7.5 minutes a,6 and there is little recovery of neurologic function? The present study was undertaken to assess the reversibility of the occlusive changes in the cerebral vasculature. The experiments were designed to see whether the vascular obstruction that is present at the end of the