Electroencephalographic patterns related to hemodynamic changes at the onset of cardio-pulmonary bypass circulation

Electroencephalographic (EEG) changes in relation to hemodynamic changes at the onset of cardio-pulmonary (C-P) bypass circulation in 31 cases undergoing open heart surgeries were studied. Rapid and extensive changes in systemic circulation, which were followed by abnormal EEGs, appeared within the first five minutes of C-P bypass. Abnormal EEG patterns including disappearance of fast waves, slowing under 6 Hz in frequency with high voltage and flattening were observed in 64% of the cases. The relations between the appearance of these abnormal EEGs and hemodynamic factors such as mean arterial pressure (mAP), central venous pressure (CVP), rate of decrease in mAP and rate of change in CVP, were analyzed in order to elucidate causes of development of the abnormal EEGs. Only the rate of decrease in mAP at the onset of C-P bypass had a high correlation (p less than 0.01) with the appearance of abnormal EEGs. The findings suggest that rapid circulatory changes in the first five minutes of C-P bypass may induce disruption of cerebral autoregulation.