Use of an EEG-bispectral closed-loop delivery system for administering propofol

Closed-loop control of propofol delivery was instituted in three patients who received a propofol infusion as part of: (Case 1) general "balanced" anesthesia, (Case 2) total intravenous anesthesia, and (Case 3) monitored anesthesia care. The bispectral index was the input variable used in a proportioned, integral and differential controller to determine the infusion rate of propofol required to maintain a stable level of hypnosis (Cases 1 and 2) or sedation (Case 3). This feedback control system provided intraoperative hemodynamic stability and a prompt recovery from the sedative-hypnotic effects of propofol.