Bispectral index-controlled postoperative sedation in cardiac surgery patients: a comparative trial between closed loop and manual administration of propofol

BACKGROUND AND OBJECTIVE: Postoperative cardiac surgery patients are usually sedated according to clinical sedation scores. Electrophysiological data derived from electroencephalography, such as the bispectral index (BIS), have been reported to assess and quantify the level of sedation, although experience in these patients is limited. In the current study, we evaluated a closed-loop system - closed-loop anaesthesia delivery system (CLADS) - for postoperative sedation after open heart surgery using BIS. METHODS: Forty-one postoperative cardiac surgery patients in the age group 18-65 years were included. In the postanaesthesia care unit, they were randomly allocated to two groups: a CLADS group, which received a continuous infusion of propofol using CLADS, and a manual group, which received propofol at a rate manually adjusted by the clinician. Propofol was administered in both groups to maintain the BIS at a target of 70 for adequate sedation. Patients were weaned from mechanical ventilation and the trachea extubated after confirmation of haemodynamic stability, haemostasis, normothermia and mental orientation. RESULTS: The percentage of total sedation time during which BIS remained within +/-10 of the target value (BIS of 70 during sedation) was significantly higher in the CLADS group than in the manual group (P = 0.002). The assessment of performance parameters using median performance error and median absolute performance error indicated better performance in the CLADS group. Manual control required the propofol infusion rate to be changed frequently, taking up considerable time and attention of the clinician. CONCLUSION: Closed-loop delivery of propofol to control BIS for postoperative sedation is feasible and efficient after cardiac surgery.