Effect of timing of morphine administration during remifentanil‐based anaesthesia on early recovery from anaesthesia and postoperative pain

Since the time to peak analgesic effect of intravenous morphine can be longer than 40–60 min in volunteers, the goal of this study was to evaluate the effect of the timing of intraoperative morphine administration on early postoperative pain. A total of 120 adult patients undergoing laparoscopic cholecystectomy were studied. Anaesthesia was induced with remifentanil and etomidate and maintained with remifentanil and sevoflurane/nitrous oxide. Morphine 150 µg kg–1 was given randomly at three different times during surgery, and a fourth group received placebo. Times to eyes opening and extubation were measured, and pain was evaluated in the post‐anaesthesia care unit (PACU) using a visual analogue scale (VAS). Morphine 2–3 mg was given when the VAS score was ≥50 mm. The four groups were, according to the time elapsed from morphine administration to the end of surgery, group 1 (n=30): placebo; group 2 (n=33): 40 min. Recovery from anaesthesia and pain scores were similar in all groups. However, mean (sd) morphine consumption was 5.7 (4.7) mg in group 1, 4.4 (4.2) mg in group 2, 4.7 (4.7) mg in group 3, and 2.2 (4.0) mg in group 4 (P