Preventing Remifentanil-Induced Hyperalgesia

The propofol infusion was stopped after skin closure, and the Ce of remifentanil was maintained as 1.0 ng.mL⁻¹ while patients were emerging from anesthesia to prevent remifentanil-induced hyperalgesia (RIH) in the S group [28 (link)]. In the M group, infusion of the RP mixture was stopped after skin closure. All patients received ketorolac (30 mg intravenously) prior to wound closure and local anesthetic wound infiltration with lidocaine for postoperative pain management. Reversal of neuromuscular function was achieved by administering sugammadex (2–4 mg.kg⁻¹) to prevent residual paralysis. When the patient regained consciousness with spontaneous and smooth respiration (TOF ratio ≥ 0.9), the endotracheal tube was removed, and the patient was sent to the post-anesthesia care unit (PACU) for further care. An independent investigator recorded the values of BIS and ANI, and the frequency of TCI device adjustments. Any bolus of remifentanil or propofol given intraoperatively was defined as a TCI pump adjustment. The hemodynamic parameters, including mean blood pressure (MBP) and HR, were recorded at baseline and at the following times: after intubation; at surgical incision; 30 min after skin incision; at the end of surgery; after extubation; and at emergence from anesthesia. Postoperative pain was assessed subjectively by the patients using a visual analogue scale (VAS) on arriving and leaving the PACU (the first postoperative hour) and on the first postoperative day [29 (link)]. When the patient’s VAS was > 4, fentanyl, 50 mcg, was given intravenously in the PACU. In this study, the RIH was defined as VAS > 4 after prescribing fentanyl ≥ 50 mcg within the first postoperative hour. The various time intervals (surgical time, anesthetic time, time for emergence); postoperative rescue analgesia; and adverse effects, such as postoperative nausea and vomiting (PONV) and RIH, were retrieved through anesthetic records and electronic medical records retrospectively. The duration of each phase was defined as follows: (1) surgical time: from skin incision to skin closure; (2) anesthetic time: from the beginning of induction to extubation; (3) time for emergence: from the end of surgery to eye-opening on verbal command; (4) overall patients’ satisfaction on postoperative day one was rated by a questionnaire using the following scale: 1, very unsatisfactory; 2, unsatisfactory; 3, neutral; 4, satisfactory; and 5, very satisfactory.