A study of the electroencephalogram during surgery with deep hypothermia and circulatory arrest in infants.

Seventeen infants (2½ to 28 months old) were continuously monitored by six-channel electroencephalography (EEG) during the entire surgical procedure of open-heart repair. They were subjected to surface hypothermia supplemented by cold extracorporeal circulation (ECC) down to an average esophageal temperature of 21° C., to cardiac arrest of 40 minutes average (range 19 to 62 minutes), and to ECC rewarming. Survival time of the EEG was correlated to esophageal temperature at the time of arrest. EEG reappeared an average of 26 minutes (5.30 to 50) after the start of rewarming ECC and became strictly continuous after 44 minutes. Reappearance latency was well correlated with the duration of arrest. Potential normalization was observed in 13 infants, but true normalization was observed in only 2 infants during the 90 to 120 minute period after ECC. By judging the EEG and by comparing this series with two previous series of moderate and deeper hypothermia in older patients, we concluded that the immediate tolerance of the brain to deep hypothermia and circulatory arrest seems no different in infants and in older patients.