Sixty patients were randomly assigned to two equal groups. Group I received epidural morphine 1 mg after surgery and used a patient-controlled analgesia device programmed to deliver morphine 0.2 mg h−1, 0.2 mg per bolus. Group II received an epidural loading dose of morphine 1 mg plus ketamine 5 mg and used a patient-controlled analgesia device programmed to deliver morphine 0.2 mg+ketamine 0.5 mg h−1, morphine 0.2 mg+ketamine 0.5 mg per bolus with a lockout time of 10 min. The mean morphine consumption was 8.6±0.7 mg for group I and 6.2±0.2 mg for group II. Although group II utilized significantly less morphine (P<0.05), pain relief was significantly better in group II than in group I (P<0.05) in the first 3 h. Vomiting occurred more frequently in group I (26%) than in group II (13%). The frequency and severity of pruritus and level of sedation were similar in the two groups. These findings suggest that patient-controlled epidural analgesia with morphine plus ketamine may provide effective analgesia with a lesser dose of morphine and fewer subsequent side effects, compared with patient-controlled epidural analgesia with morphine alone after lower abdominal surgery.

Thirty-eight ASA I–III patients undergoing lower abdominal operations were randomly allocated to receive either morphine (group M, patient-controlled analgesia bolus=1 mg of morphine) or tramadol (group T, patient-controlled analgesia bolus=10 mg of tramadol) for post-operative patient-controlled analgesia (PCA) after receiving morphine intraoperatively. There were no between-group differences in the pain, sedation or vomit scores. The nausea scores were significantly higher in group T in the initial 20 h and between 32 and 36 h (P<0.01, 0–4 and 8–12 h; P<0.05, 4–8, 12–16, 16–20 and 32–36 h). The incidence of dizziness was also significantly higher in group T (68.4% vs. 31.6%, group T vs. group M, P<0.05). There was no difference in the overall satisfaction. We conclude that the use of tramadol, compared with morphine, for post-operative PCA after intraoperative loading with morphine is associated with more nausea and dizziness, but with similar sedation, quality of analgesia and patient satisfaction.