Closed-loop control of anesthesia using the bispectral index in open heart surgery

The introduction of the bispectral index (BIS) as a comprehensive indicator of depth of anesthesia has prompted research in the automated delivery of anesthetics. This trial aimed to evaluate the usefulness of the BIS as the feedback variable in a closed-loop anesthesia control system during cardiac surgery under cardiopulmonary bypass (CPB).

Thirty-four adult patients of American Society of Anesthesiologists grade I-III undergoing elective cardiac surgery under hypothermic CPB were evaluated prospectively in a tertiary care teaching hospital. The anesthesia was induced and maintained throughout surgery using a closed-loop anesthesia delivery system (502/DEL/2003) to control the BIS.

The closed-loop system was functional during 96% of the anesthesia duration. The BIS was maintained at +/- 10 of the target of 50 during 86% of the automated anesthesia. The closed-loop system was also functional during CPB despite a fall in BIS probably resulting from hypothermia. None of the patients had recall of events or experiences during the procedure.

The closed-loop control of anesthetic delivery adjusted to BIS is feasible and may be useful in open heart surgery under hypothermic CPB.