Pre-emptive analgesic efficacy of tramadol compared with morphine after major abdominal surgery

Background. Studies of pre-emptive analgesia in humans haveshown conflicting results. This prospective, randomized, double-blind,controlled study was designed to test the hypothesis that areduction in postoperative morphine consumption can be achievedby tramadol administered after induction of anaesthesia. Methods. Ninety patients were allocated randomly to receivei.v. tramadol (1 mg kg^–1) (Group T), morphine(0.1 mg kg^–1) (Group M) or saline 2 ml(Group S) after induction of anaesthesia. At peritoneal closure,a standardized (0.1 mg kg^–1) morphine loadingdose was given to all patients for postoperative pain management.Patients were allowed to use a patient-controlled analgesia(PCA) device giving bolus doses of morphine 0.025 mg kg^–1.Discomfort, sedation, pain scores, cumulative morphine consumption,and side-effects were recorded at 1, 2, 6, 12 and 24 hafter the start of PCA. Results. There were no significant differences between groupsin mean pain, discomfort, and sedation scores at any study period.Cumulative morphine consumption was significantly lower in GroupM at 12 and 24 h after starting the PCA than in Group S.In Group T, it was lower only after 24 h (28% less in GroupM and 17% less in Group T; P<0.017). There were no significantdifferences in morphine consumption between Groups T and M. Conclusions. Tramadol (1 mg kg^–1), administeredafter induction of anaesthesia, offered equivalent postoperativepain relief, and similar recovery times and postoperative PCAmorphine consumption compared with giving morphine 0.1 mg kg^–1.These results also suggest that presurgical exposure to systemicopioid analgesia may not result in clinically significant benefits Br J Anaesth 2003; 91: 209–13