FOCAL CEREBRAL INFARCTION IN CATS IN THE PRESENCE OF HYPERGLYCEMIA AND INCREASED INSULIN

Although it has been well established that hyperglycemia increases cerebral damage following transient cerebral ischemia, its effect on permanent focal ischemia is controversial. We hypothesized that other factors associated with hyperglycemia, such as plasma insulin, may alter the brain's response to hyperglycemia. The objective of this study was to determine if hyperglycemia changes infarction size following 8 hr of middle cerebral artery occlusion in the anesthetized cat and to examine if changes in plasma insulin levels alter hyperglycemia's effects. Infarct size in hyperglycemic cats with increased plasma insulin (38.3 +/- 8.4%, mean +/- SE) or in hyperglycemic cats without increased plasma insulin (30.5 +/- 7.6%) was not significantly different from that of ischemic controls (33.8 +/- 2.8%). However, the variability in infarct size tended to be greater (P = 0.0647) among all hyperglycemic cats compared to control animals. The source of the variability is unknown, but this observation combined with the findings of others suggests the possibility that the effect of hyperglycemia is dependent on the exact nature of the focal ischemic insult (i.e., degree of collateral blood supply) and that this effect may vary greatly from individual to individual within a population.