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ANESTHETIC PHARMACOLOGY

The Accuracy and Clinical Feasibility of a New Bayesian-Based Closed-Loop Control System for Propofol Administration Using the Bispectral Index as a Controlled Variable

Tom De Smet, MSc^*, Michel M. R. F. Struys, MD, PhD, Martine M. Neckebroek, MD, Kristof Van den Hauwe, MD, Sjoert Bonte, BSc, and Eric P. Mortier, MD, DSc

From the *Demed Engineering, Temse, Belgium; Department of Anesthesia, Ghent University Hospital, Ghent; Departments of Anesthesia, Ghent University, Ghent, Belgium and Department of Anesthesia, University Medical Center, Groningen, the Netherlands.

Address correspondence and reprint requests to Prof. Dr. Michel M. R. F. Struys, Department of Anesthesiology, University Medical Center Groningen, Groningen, The Netherlands. Address e-mail to m.m.r.f.struys{at}anest.umcg.nl.

BACKGROUND: Closed-loop control of the hypnotic component of anesthesia has been proposed in an attempt to optimize drug delivery. Here, we introduce a newly developed Bayesian-based, patient-individualized, model-based, adaptive control method for bispectral index (BIS) guided propofol infusion into clinical practice and compare its accuracy and clinical feasibility under direct observation of an anesthesiologist versus BIS guided, effect compartment controlled propofol administration titrated by the anesthesiologist during ambulatory gynecological procedures.

METHODS: Forty ASA patients were randomly allocated to the closed-loop or manual control group. All patients received midazolam 1 mg IV and alfentanil 0.5 mg IV before induction. In the closed-loop control group, propofol was administered using the previously described closed-loop control system to reach and maintain a target BIS of 50. In the manual control group, the propofol effect-site concentration was adapted at the discretion of the anesthesiologist to reach and maintain a BIS as close as possible to 50. Induction characteristics, performance, and robustness during maintenance and recovery times were compared. Hemodynamic and respiratory stability were calculated as clinical feasibility parameters.

RESULTS: The closed-loop control system titrated propofol administration accurately resulting in BIS values close to the set point. The closed-loop control system was able to induce the patients within clinically accepted time limits and with less overshoot than the manual control group. Automated control resulted in beneficial recovery times. Our closed-loop control group showed similar acceptable clinical performance specified by similar hemodynamic, respiratory stability, comparable movement rates, and quality scores than the manual control group.

CONCLUSIONS: The Bayesian-based closed-loop control system for propofol administration using the BIS as a controlled variable performed accurate during anesthesia for ambulatory gynecological procedures. This control system is clinical feasibility and can be further validated in clinical practice.

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