DONLEY, ROBERT F.

Regional cerebral blood flow (CBF) was measured (intra-arterial injections of 133 Xe) and electroencephalograms (EEG) were recorded periodically before, for two hours during, and for one and one-fourth hours after middle cerebral artery (MCA) occlusion in 20 squirrel monkeys ( Saimiri sciureus ). A CBF-Pa co co2 response curve for these animals under barbiturate anesthesia was created from CBF values prior to MCA occlusion and during the time a steady state was being achieved. The animals were subdivided into four groups (five monkeys in each) on the basis of Pa co co2 values: 20, 36, 40, and 60 mm Hg. CBF values from this study were compared to previous results obtained with 35 Kr. The phenomenon of "look through" and the importance of recognizing this artifact and its significance in analyzing CBF results in areas of focal ischemia are discussed. The present results were correlated with cerebral ATP and lactate concentrations in ischemic regions determined in previous studies using this preparation at these Pa co co2 values and at comparable time intervals before, during, and after MCA occlusion. The EEG appears to reflect the state of ischemic brain accurately. However, CBF measured by the 133 Xe method can be misleading in regard to the true degree of ischemia resulting from occlusion of an intracranial vessel and cannot be relied on to demonstrate accurately "steal" or "reverse steal" due to changes in Pa co co2 .

The effect of large dosages of dexamethasone on the edema of cerebral ischemia and infarction in the squirrel monkey after temporary occlusion of the middle cerebral artery is reported. There was no difference between the ten monkeys treated with dexamethasone and the 11 control animals in clinical course, mortality, morbidity, histological appearance, or amount of edema associated with this ischemic lesion. The differences in the electron microscopic and pathophysiological findings of the edema from ischemia secondary to single major vessel occlusion and in the edema from an intracranial mass lesion are reviewed. The possible therapeutic or pharmacological effects of steroids are considered along with available data on lysosomes in the brain. At the present time, there is no justification for the use of large doses of dexamethasone in the treatment of cerebral infarction.