Regional cerebral blood flow thresholds during cerebral ischemia.

The development of methods of determining regional cerebral blood flow (rCBF) has made possible the determination of thresholds for the appearance of cerebral ischemia. These thresholds vary depending on the method used for assessing cerebral ischemia. The following thresholds have been determined in man and nonhuman primates: 20 cc/100 g per min, electroencephalogram (EEG) and evoked cortical potential abnormalities appear, paralysis seen in waking monkeys; 15 cc/100 g per min. EEG and evoked cortical potential are lost; 12 cc/100 g per min, flows at this level in excess of 120 min produce infarction in waking animals; and 6 cc/100 g per min, massive loss of intracellular [K+]. The residual rCBF and the duration of ischemia determine the appearance of infarction in waking Macaca irus monkeys.