A randomized controlled trial demonstrates that a novel closed-loop propofol system performs better hypnosis control than manual administration.

PURPOSE: The purpose of this randomized control trial was to determine the performance of a novel rule-based adaptive closed-loop system for propofol administration using the bispectral index (BIS(R)) and to compare the system's performance with manual administration. The effectiveness of the closed-loop system to maintain BIS close to a target of 45 was determined and compared with manual administration.

METHODS: After Institutional Review Board approval and written consent, 40 patients undergoing major surgery in a tertiary university hospital were allocated to two groups using computer-generated block randomization. In the Closed-loop group (n = 20), closed-loop control was used to maintain anesthesia at a target BIS of 45, and in the Control group (n = 20), propofol was administered manually to maintain the same BIS target. To evaluate each technique's performance in maintaining a steady level of hypnosis, the BIS values obtained during the surgical procedure were stratified into four clinical performance categories relative to the target BIS: < or = 10%, 11-20%, 21-30%, or > 30% defined as excellent, good, poor, or inadequate control of hypnosis, respectively. The controller performance was compared using Varvel's controller performance indices. Data were compared using Fisher's exact test and the Mann-Whitney U test, P < 0.05 showing statistical significance.

RESULTS: In the Closed-loop group, four females and 16 males (aged 54 +/- 20 yr; weight 79 +/- 7 kg) underwent anesthesia lasting 143 +/- 57 min. During 55%, 29%, 9%, and 7% of the total anesthesia time, the system showed excellent, good, poor, and inadequate control, respectively. In the Control group, five females and 15 males (aged 59 +/- 16 yr; weight 75 +/- 13 kg) underwent anesthesia lasting 157 +/- 81 min. Excellent, good, poor, and inadequate control were noted during 33%, 33%, 15%, and 19% of the total anesthesia time, respectively. In the Closed-loop group, excellent control of anesthesia occurred significantly more often (P < 0.0001), and poor and inadequate control occurred less often than in the Control group (P < 0.01). The median performance error and the median absolute performance error were significantly lower in the Closed-loop group compared with the Control group (-1.1 +/- 5.3% vs -10.7 +/- 13.1%; P = 0.004 and 9.1 +/- 1.9% vs 15.7 +/- 7.4%; P < 0.0001, respectively).

CONCLUSION: The closed-loop system for propofol administration showed better clinical and control system performance than manual administration of propofol. (Clinical Trials gov. NCT 01019746).