A COMPARISON OF REMIFENTANIL AND MORPHINE-SULFATE FOR ACUTE POSTOPERATIVE ANALGESIA AFTER TOTAL INTRAVENOUS ANESTHESIA WITH REMIFENTANIL AND PROPOFOL

Background. The transition from remifentanil intraoperative anesthesia to postoperative analgesia must be planned carefully due to the short duration of action (3-10 min) of remifentanil hydrochloride, a potent , esterase-metabolized mu- opioid agonist. This study compared the eff icacy and safety of transition regimens using remifentanil or morphine sulfate for immediate postoperative pain relief in patients who had s urgery under general anesthesia with remifentanil/propofol. Methods: O ne hundred fifty patients who had received open-label remifentanil and propofol for intraoperative anesthesia participated in this multicent er, double-blind, double-dummy study and were randomly assigned to eit her the remifentanil (R) group or the morphine sulfate (M) group. Twen ty minutes before the anticipated end of surgery, the propofol infusio n was decreased by 50%, and patients received either a placebo bolus ( R group) or a bolus of 0.15 mg/kg morphine (M group). At the end of su rgery, the propofol and remifentanil maintenance infusions were discon tinued and the analgesic infusion was started: either 0.1 mu g.kg(-1). min(-1) remifentanil (R group) or placebo analgesic infusion (M group) . During the 25 min after tracheal extubation, remifentanil titrations in increments of 0.025 mu g.kg(-1).min(-1) and placebo boluses (R gro up), or 2 mg intravenous morphine boluses and placebo rate increases ( M group) were administered as necessary at 5-min intervals to control pain. Patients received the 0.075 mg/kg intravenous morphine bolus (R group) or placebo (hi group) at 25 and 30 min after extubation, and th e analgesic infusion was discontinued at 35 min. From 35 to 65 minutes after extubation, both groups received 2-6 mg open-label morphine ana lgesia every 5 min as needed. Results: Successful analgesia, defined a s no or mild pain with adequate respiration (respiratory rate [RR] gre ater than or equal to 8 breaths/ min and pulse oximetry greater than o r equal to 90%), was achieved in more patients in the R group than in the M group (58% vs. 33%, respectively) at 25 min after extubation (P < 0.05). The median remifentanil rate for successful analgesia was 0.1 25 mu g.kg(-1).min(-1) (range, 0.05-0.23 mu g.kg(-1).min(-1)), and the median number of 2-mg morphine boluses used was 2 (range, 0-5 boluses ). At 35 min after extubation, greater than or equal to 74% of patient s in both groups experienced moderate to severe pain. Median recovery times from the end of surgery were similar between groups. Transient r espiratory depression, apnea, or both were the most frequent adverse e vents (14% for the R group vs. 6% for the M group; P > 0.05). Conclusi ons: Remifentanil provided safe and effective postoperative analgesia when administered at a final rate of 0.05-0.23 mu g.kg(-1).min(-1) in the immediate postextubation period. Remifentanil provided more effect ive postoperative analgesia than did intraoperative treatment with mor phine (0.15 mg/kg) followed by morphine boluses (less than or equal to five 2-mg boluses). The effects of remifentanil dissipated rapidly af ter ending the infusion, and alternate analgesia was required. Further studies are underway to define transition regimens that will improve postoperative analgesia in patients receiving anesthesia with remifent anil.