Electroencephalographic and plasma electrolyte changes after cardiac surgery in children.

Serial electroencephalographic studies were carried out during the first few days following open heart surgery in 53 children who had an uneventful surgical procedure and postoperative recovery. While the E.E.G. taken a few hours after the end of the operation was comparable to the preoperative one, an increase in slow activity subsequently occurred in all patients and reached its maximum on the first or second postoperative day. This increase in slow activity was not commonly associated with any obvious altered state of consciousness and the preoperative E.E.G. patterns reappeared within one week. A fall in plasma sodium level with a comparable fall in plasma chloride usually occurred around the second postoperative day, returning to the preoperative levels by the fourth postoperative day.It is suggested that both events are part of a normal reversible physiological response to the operative trauma. The presence of generalized slow activity in the E.E.G. in the first few days after heart surgery does not necessarily imply that there has been cerebral damage from anoxia.