Intravenous tramadol versus epidural morphine for postthoracotomy pain relief: a placebo-controlled double-blind trial.

Tramadol, an analgesic deriving only part of its effect via opioid agonist activity, might provide postoperative pain relief with minimal risk of respiratory depression. We, therefore, evaluated it for the control of postthoracotomy pain. In this randomized, double-blind study, a single intravenous (IV) bolus dose of 150 mg tramadol (Group T) was compared to epidural morphine administered as an initial 2-mg bolus and subsequent continuous infusion at a rate of 0.2 mg/h (Group M). Patients in each group could receive morphine IV from a patient-controlled analgesia (PCA) device. Pain scores, morphine consumption, arterial blood gases, and vital capacity values were recorded at regular intervals postoperatively until 8:00 AM on the first postoperative day. Both groups obtained adequate pain relief, and there were no between-group differences in pain scores or PCA morphine consumption. Pao2 was significantly higher in Group T at 2 h and Paco2 significantly higher in Group M at 4 h postoperatively. There were no other significant respiratory differences. We conclude that a single dose of 150 mg tramadol given at the end of surgery provided postoperative analgesia equivalent to that provided by this dosage regimen of epidural morphine for the initial postoperative period.