The effects of global normothermic hypoperfusion on the processed electroencephalogram in patients

This study examined the effects of global normothermic hypoperfusion on the compressed spectral array (CSA) processed electroencephalogram (EEG) during high-dose narcotic anesthesia. Fifteen patients undergoing cardiac electrophysiologic surgery were studied. The patients were anesthetized with a standard high-dose narcotic technique and then connected to a Nicolet Pathfinder I CSA EEG analysis system using seven subdermal electrodes in a modified International 10-20 configuration. There were 167 intervals of profound hypotension ranging from 8 to 96 seconds. During these periods the cerebral perfusion pressure was almost zero. Despite 38 intervals up to 32 seconds long, 6 of the 15 patients had no EEG changes. Overall, there were 36 (21.6%) ischemic EEG recordings. None of the patients developed neurological complications. The incidence of EEG changes was much lower than expected from other studies. Either the processed EEG was inherently insensitive, the high-dose narcotic masked the processed EEG effects of hypoperfusion, or the narcotic provided a previously unknown protective effect.