[Morphine infusion for postoperative pain management in patients who have undergone upper abdominal surgery]

We compared the efficacy and side effects of postoperative continuous infusions versus intermittent intravenous on-demand morphine, with or without the addition of clonixin. Eighty five healthy patients, aged 18 to 65 years, scheduled for elective cholecystectomy, were prospectively randomized: Group 1 (n = 22) received morphine 2.5 mg i.v. on-demand; group 2 (n = 22) received a clonixin 400 mg/day i.v. infusion; group 3 (n = 19) a morphine 0.4 mg/kg/day i.v. infusion; and group 4 (n = 22) received a clonixin 400 mg/day plus a morphine 0.4 mg/kg/day i.v. infusion. Groups 2, 3 and 4 also received, on-demand, 2.5 mg i.v. bolus doses of morphine. A blind observer recorder analogue and descriptive pain scores, respiratory rates and side-effects for 72 hours postoperatively. Groups with morphine infusions had less overall pain scores for the first day when compared with intermittent dosing (p < 0.05); these groups also had less pain during the night (p = 0.0016) and required less additional morphine (p < 0.0001). Side-effects were similar and no cases of heavy sedation or respiratory depression were observed. We conclude that a morphine 0.4 mg/kg/day infusion is a safe and effective alternative to on demand dosing in healthy patients after elective cholecystectomy, achieving better analgesia without increasing side-effects. Clonixin 400 mg/day seems to add no significant benefits.