Fatal strokes in hyperglycemic cats

Hyperglycemia is associated with three- to fourfold larger infarcts than normoglycemia following permanent middle cerebral artery occlusion in cats. We investigated the effects of glycemia on brain outcome when middle cerebral artery blood flow was restored (clip release) after 4 hours of occlusion. Seven of 13 hyperglycemic (22 mM) and one of 12 normoglycemic (6 mM) anesthetized cats developed total middle cerebral artery territory infarcts and hemispheric edema and died of brainstem compression. The remaining six and 11 cats recovered fully and later showed no or only small infarcts. Compared with permanent occlusion, restoration of blood flow after 4 hours reduced infarct volume in all normoglycemic and hyperglycemic cats that survived, but caused a much higher proportion (54% vs. 17%) of hyperglycemic and, for the first time, one normoglycemic cat, to die of infarct extension, hemorrhagic infarct conversion, and total territory edema. Thus, clip release after 4 hours caused some cats to show reduced and others to show augmented tissue damage. Rendering cats hyperglycemic substantially worsened their outcome after reperfusion by increasing their death rate from total territory edema sevenfold. Our results demonstrate that risk/benefit analyses for recanalization efforts in humans should take serum glucose concentrations into account.