THE APPEARANCE OF REGIONAL VARIATIONS IN METABOLISM AT A CRITICAL LEVEL OF DIFFUSE CEREBRAL OLIGEMIA

Increased intracranial pressure was used to produce graded cerebral oligemia in the rabbit. When cerebral perfusion pressure (CPP) was 40 Torr or above, oligemia was not severe enough to cause a decrease in ATP. When CPP was 20 Torr or below, a rapid depletion of ATP occurred. When CPP equalled 30 Torr, animals were distributed at the two extremes, with pronounced diminution of ATP correlating with loss of electrical activity and with increased NADH tissue fluorescence. In addition this critical stage of oligemia was marked by the appearance of regional variations in metabolism. Furthermore, ischemic regions could be visualized in sections of frozen brain by virtue of increased NADH fluorescence.