The neurologic implications of diabetic hyperglycemia during surgical procedures at increased risk for brain ischemia

The neurologic implications of diabetic hyperglycemia depend on whether the ischemic insult is permanent or temporary. Laboratory studies show that following permanent focal ischemia, a situation analogous to stroke, diabetic hyperglycemia is protective in the penumbral region, whereas it may slightly increase infarct size. In addition, clinical studies cannot unequivocally attribute poor outcome in diabetic stroke patients to hyperglycemia. Thus, both laboratory and clinical studies have been unable to define a cause and effect relationship between diabetic hyperglycemia and neurologic outcome following stroke. On the other hand, diabetic hyperglycemia is an important determinant of neurologic outcome following temporary focal ischemia (analogous to temporary occlusion of a cerebral vessel) and global ischemia (analogous to circulatory arrest). Based on laboratory studies, aggressive insulin-based blood glucose management with the goal of euglycemia is imperative prior to temporary ischemia. However, intraoperative ischemic events are overwhelmingly of a permanent focal nature, and the neurologic implications of diabetic hyperglycemia for the vast majority of surgical procedures at increased risk for brain ischemia are minimal. It is only in circumstances where temporary focal or global ischemia are used as part of the surgical procedure that aggressive insulin-based blood glucose management is warranted.