OBJECTIVETo compare the analgesic effect and side effects of morphine for intravenous patient-controlled analgesia (PCA) with or without low-dose naloxone after abdominal surgery.

METHODSFifty-nine ASA I - II patients undergoing elective abdominal surgery were randomly divided into two groups: group morphine received postoperative PCA with 0.4 mg/ml morphine (a 1 mg bolus with a 5 min lockout), group naloxone received morphine 0.4 mg/ml with 6 microg/kg naloxone. Blood pressure, heart rate, respiratory rate, and pulse oxygen saturation were monitored. Visual analogue scale (VAS), nausea/vomiting, pruritus, sedation and consumption of morphine were recorded for 24 hours.

RESULTSVAS had no difference between group morphine and group naloxone, but group naloxone had significantly lower VAS for pain at rest or movement (beyond 4-8 h), and the incidence of nausea/vomiting significantly decreased in group naloxone (P < 0.05). No differences existed in pruritus, sedation, respiratory rate, and hemodynamic parameters between these two groups. The 24 hours postoperative morphine consumption was (36.6 +/- 13.5) mg in group naloxone and (43.7 +/- 14.6) mg in group morphine (P < 0.05).

CONCLUSIONFor morphine PCA, morphine with 6 microg/kg naloxone is effective in preventing some PCA morphinerelated side effects. Naloxone not only reduces postoperative morphine requirements but also improves the analgesic effect.