Closed loop control of sedation for colonoscopy using the Bispectral Index*

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Abstract
Summary Sixteen patients undergoing colonoscopy were sedated with propofol using a closed‐loop control system guided by the Bispectral Index (BIS). Propofol administration, via a target‐controlled infusion, was controlled by a proportional‐integral‐differential control algorithm. The median (range) propofol target concentration during closed‐loop control was 2.3 (1.7–3.6) µg.ml−1. The performance characteristics of the system were excellent, with a median absolute performance error of 7 (1–15)%. Patients were drowsy yet rousable, with a median (range) BIS set‐point of 80 (75–85). No patient became apnoeic, required airway support or became haemodynamically unstable whilst sedated. Eight patients moaned or moved during colonoscopy and four had recall. Median (range) time to full consciousness was 4 (2–20) min after the end of closed‐loop control. Patient and surgeon satisfaction were high. We conclude that BIS may be a suitable control variable for closed‐loop control of sedation with propofol.