Some aspects of electroencephalographic changes during open‐heart surgery

OPEN-HEART SURGERY with extracorporeal circulation and hypothermia has opened up a new world of physiology, which certain authors' have termed neophysiology. Brain tissue being more sensitive to oxygen lack than any other tissue, the central problem is how to maintain normal cerebral activity. The action of the heart and lungs are subservient to this end. The electrical activity of the brain may fluctuate from minute to minute and even from second to second, and the electroencephalogram is therefore the most sensitive monitor of brain function available. Since it is affected by temperature, anesthesia, blood flow, and blood chemistry, these data must be known in order to interpret the electroencephalographic fluctuations correctly. Although many studies have been carried out, understanding of the hemodynamic and biochemical factors concerned is still incomplete. The problem is complex because the factors are multiple; straightforward cause-and-effect deductions are not always possible. Although some of our interpretations must remain provisional, it seems worth recording our experience because certain perfusion teams do not find electroencephalographic monitoring necessary, while others consider it useful and indeed essential.