Adequacy of anesthesia monitoring using entropy and surgical pleth index with dexmedetomidine versus fentanyl in supratentorial tumor surgery: A retrospective study

Background: Anesthetic management for supratentorial tumor surgery requires precise control of hypnotic depth and nociception to maintain cerebral physiology, facilitate neuromonitoring, and allow early neurological assessment. Conventional hemodynamic parameters inadequately reflect anesthetic adequacy. The adequacy of anesthesia (AoA ™ ) monitoring system integrates state entropy (SE) and surgical pleth index (SPI) to simultaneously assess hypnotic depth and nociception-antinociception balance. Methods: This retrospective observational study reviewed anesthesia records of 100 patients who underwent elective supratentorial tumor excision between August 2021 and April 2024. Patients received inhalational anesthesia with either fentanyl (Group F) or dexmedetomidine (Group D) as an adjuvant. AoA monitoring was used intraoperatively, with the target zone defined as SE 40–60 and SPI 20–50. The primary outcome was the duration and proportion of intraoperative time spent within the AoA target zone. Secondary outcomes included intraoperative hemodynamics, rescue analgesic requirements, recovery characteristics, and postoperative pain. Results: Group D demonstrated a significantly greater absolute duration within the AoA target zone compared with Group F (150.9 ± 49.28 min vs. 125.7 ± 68.5 min; p = 0.04) and a higher proportion of time within the target zone (62.42 ± 14.3% vs. 50.53 ± 21.42%; p = 0.002). Periods of mismatch between hypnotic depth and analgesia were more frequent in Group F. Intraoperative hemodynamics, rescue fentanyl requirements, brain relaxation scores, recovery profiles, and postoperative pain scores were comparable between groups. Conclusion: Dexmedetomidine, when used as an adjuvant to inhalational anesthesia under AoA-guided monitoring, was associated with more consistent maintenance of balanced anesthetic depth and nociception compared with fentanyl, without adverse effects on hemodynamics or recovery. Prospective randomized studies are required to further validate these findings.