EEG-Derived Entropy Monitoring During Propofol Sedation for ERCP: Sedation Profiles, Age-Related Effects, and Implications for Procedure-Specific Target Ranges

Background and Objectives: Conventional EEG-derived sedation targets for Entropy monitoring (State Entropy SE 40–60) were established in the context of general anaesthesia and may not be directly applicable to procedural sedation for endoscopic retrograde cholangiopancreatography (ERCP). This study aimed to characterize SE and Response Entropy (RE) trajectories during propofol-based sedation for ERCP and to evaluate their relationships with clinical sedation depth, patient characteristics, and procedural outcomes. Materials and Methods: In this prospective, single-center observational study, 50 consecutive adult patients undergoing elective ERCP under propofol-based sedation were enrolled. SE and RE were recorded at baseline and at serial intra-procedural timepoints. Time-in-zone analysis classified SE values into predefined ranges. Correlations between Entropy indices and MOAA/S scores, patient factors, Aldrete recovery scores, and adverse events were assessed using Spearman’s rank correlation. Results: The median patient age was 72.5 years (IQR 65.0–79.0), and the median ASA score was 3 (IQR 2–3). Following induction, SE declined from a baseline mean of 89.3 ± 1.5 to a mean of 68.8 ± 5.3 at 10 min, the lowest group-level value recorded; the mean individual SE nadir across patients was 67.2 ± 5.3. No SE values below 40 were observed at any timepoint. Mean time spent within the conventional SE 40–60 target range was 3.7% ± 10.6, while mean time within SE 60–85 was 80.7% ± 8.3. SE at 3 min correlated moderately with MOAA/S at 3 min (Spearman rho = 0.430, p = 0.002), with substantial within-category variability. Age showed a strong negative correlation with SE at 3 min (rho = −0.612, p < 0.001), an effect that persisted at 5 min, consistent with deeper early EEG suppression in older patients, which may reflect increased pharmacodynamic sensitivity, age-related changes in spectral substrate, or both. ASA score was associated with SE at 15 min only (rho = −0.299, p = 0.035). Patients who experienced adverse events demonstrated higher SE instability, though differences did not reach statistical significance. Recovery was rapid, with a median Aldrete score of 10 at 15 min. Conclusions: During propofol sedation for ERCP, observed SE values operated predominantly between 60 and 85, well above the conventional general anaesthesia target of 40–60. Older age was the strongest predictor of early sedation depth. These findings suggest that in elderly, high-ASA patients receiving propofol-based multi-drug sedation for ERCP, numerical SE values differ systematically from conventional general anaesthesia-derived target ranges. Whether this reflects true procedure-specific sedation requirements or cohort-specific spectral substrate differences warrants prospective outcome-anchored investigation.