EFFECTS OF CARDIOPULMONARY BYPASS AND HYPOTHERMIA ON ELECTROENCEPHALOGRAPHIC VARIABLES

We studied the effects of hypothermia and cardiopulmonary bypass (CPB) on four depth of anaesthesia monitors; spectral edge frequency (SEF), median frequency (MF), bispectral index (BIS) and auditory evoked pot ential index (AEPIndex) in 12 patients during uneventful cardiac anaes thesia. Each variable was recorded simultaneously at 10 periods during anaesthesia. All four variables were not affected by the transition t o CPB. During hypothermia, values of AEPIndex, MF and SEF were tightly distributed but values of BIS were very variable and overlapped with those before induction of anaesthesia. The variability decreased durin g rewarming. The values of AEPIndex throughout the anaesthesia never o verlapped with those before induction of anaesthesia. The AEPIndex was the most stable and reliable as a depth of anaesthesia monitor among the four variables in cardiac bypass surgery.