BACKGROUND: The bispectral index (BIS) has been shown to be useful for monitoring the degree of hypnosis in anesthetized adults. Although several studies have been performed to evaluate BIS in pediatric patients, it is unclear whether a BIS monitor can be applied in infants. This study was designed to evaluate changes of BIS, mean arterial pressure and heart rate during anesthesia with sevoflurane or midazolam in pediatric open heart surgery patients.

METHODS: Eighteen patients under 3 years of age scheduled for an elective cardiac surgery were studied. Group S (n = 9) received sevoflurane-fentanyl, group M (n = 9) received midazolam-fentanyl. BIS, mean arterial pressure, heart rate, temperature, and end-tidal sevoflurane concentrations were obtained during anesthesia and surgery including cardiopulmonary bypass. The amount of fentanyl injected on an as needed base, total mechanical ventilation duration and intensive care unit stay were compared.

RESULTS: A significant overall association between BIS and temperature was observed (Group S; R² = 0.309, Group M; R² = 0.225). There were no correlation between BIS and mean arterial pressure, heart rate, end-tidal sevoflurane concentration, and were no difference in the BIS scores of the groups. The mean arterial pressure of the M group from incision to CPB and post CPB 30 minutes were greater than those of the S group. The dose of fantanyl injected as needed during operation was greater in the M group than in the S group. No significant differences in the perisod of ventilation care and ICU stay.

CONCLUSIONS: BIS decreased in both groups of patients as temperature decreased. Midazolam and fentanyl anesthesia in congenital heart disease may cause insufficient anesthesia regardless of BIS scores.