Electroencephalographic evidence of cerebral ischemia during acute extracorporeal hypoperfusion

Although the incidence of neurologic complications after cardiopulmonary bypass appears to be decreasing, such complications continue to occur regardless of the perfusion techniques employed. In order to assess the ischemic potential of brief episodes of hypoperfusion, eight-channel EEG power spectra were recorded from 15 patients undergoing high-pressure, high-flow extracorporeal perfusion. Reductions in flow were performed 49 times to facilitate surgical manipulations, and on ten occasions (20%) resulted in EEG evidence of cerebral ischemia. Such ischemia was observed in 6 of 18 (33%) episodes during normothermia, but 0 of 18 episodes during stable hypothermia. In 4 of 13 (31%) cases of hypoperfusion during cooling at the start of cardiopulmonary bypass, EEG evidence of cerebral ischemia was also observed. These results indicate that brief episodes of hypoperfusion during normothermia or incomplete hypothermia often produce electroencephalographic evidence of cerebral ischemia.