General anesthesia and/or deep hypnotic state in propofol-based conscious sedation for endoscopy

Although moderate sedation (defined as a depression of consciousness with the retention of the ability to respond purposefully to verbal commands) is the goal in endoscopy, the exact depth of sedation reached in practice has not been well described.

In this prospective cohort study using bispectral index (BIS) monitoring to assess the depth of propofol-based sedation for same-day bidirectional endoscopy, we measured the incidence and time spent with a BIS score <60, corresponding to general anesthesia (GA) with a low probability of consciousness, and <40, corresponding to a deep hypnotic state, as defined by the American Society of Anesthesiologists.

Of 95 consecutive patients enrolled, 84 patients (88%) had a BIS score <60 and 12 patients (12.6%) a BIS score <40. The mean time patients spent under GA and in a deep hypnotic state was 9.1 ± 6.9 and 3.0 ± 2.0 minutes, respectively, representing 38% and 12.6%, respectively, of the total sedation time. Significant alcohol use (defined as >7 drinks per week) was the only predictor for dips in the BIS score <40 (16.7% of those who experienced dips were heavy alcohol users compared with 2.4% of those who did not experience dips, P = .045). A BIS score <60 was more common in younger patients (mean age, 53.8 years vs 62.6 years, P = .040). Patients who experienced a BIS score <40 had a higher incidence of postprocedural dizziness, which was assessed at discharge and at 24 hours (25% vs 7.2%, P = .028). Younger age was the only predictor for a BIS score <60 in the multivariate analysis, with an odds ratio of .921 (95% confidence interval, .863-.983; P = .013). No significant predictors were identified for a BIS score <40 in the multivariate analysis.

An important proportion of patients experience periods of GA and/or a deep hypnotic state during endoscopy. However, no predictive factors could be identified. Further studies are required to identify predictors and consequences of deep sedation and improved methods of monitoring.