A comparison of patient-controlled and intramuscular morphine in patients after abdominal surgery

This prospective, randomized study compared the effects of two methods of morphine administration after abdominal surgery in 62 adults. All patients were offered intravenous morphine in the Postanesthesia Care Unit. On the ward, one group (PCA-CI) received a continuous infusion of morphine that could be supplemented by a patient-controlled bolus every 10 minutes. The other group (IM) received intramuscular morphine (0.08-0.12 mg/kg) as often as every 3 hours when requested. During three postoperative interviews, patients were questioned about pain relief (visual analogue scale), adverse opioid effects, and satisfaction with the method of analgesia. Total dose of morphine (mg, mg/kg body weight), time to first oral analgesic medication, length of hospital stay, and cost were calculated following discharge. There was a wide interindividual variation in reported pain intensity and morphine usage in both groups. Comparison of both groups demonstrated no significant differences in analgesia, incidence of adverse opioid effects, 24 and 36 hour morphine dose, time to first oral analgesic medication, operating cost, and length of hospital stay. Patients in the PCA-CI group received a slightly greater dose of morphine in relation to body weight (24 hr, P = 0.03; 36 hr, P = 0.05) and reported a greater degree of satisfaction at each assessment (P = 0.005, P = 0.02, P = 0.01). These data support the greater patient satisfaction associated with patient-controlled analgesia but suggest that the wide range of reported pain scores and morphine requirements makes it difficult to demonstrate, in a small population, superior pain relief from patient-controlled analgesia when nurses are encouraged to administer intramuscular pain medication more effectively.