Tramadol Infusion for Postthoracotomy Pain Relief: A Placebo-Controlled Comparison with Epidural Morphine Mark B. Bloch, FCA (SA)*, Robert A. Dyer, FCA (SA)*, Sylvia A. Heijke, FCA (SA)*, and Michael F. James, PhD*† *Department of Anesthesia, Groote Schuur Hospital, Cape Town, South Africa; and †University of Cape Town, Cape Town, South Africa We compared continuous IV tramadol as an alternative to neuraxial or systemic opioids for the management of postthoracotomy pain in a prospective, randomized, double-blinded, controlled study. General anesthesia was supplemented by thoracic epidural analgesia with 0.25% bupivacaine. At rib approximation, patients received one of the following: IV tramadol (150-mg bolus followed by infusion, total 450 mg/24 h, n = 29), epidural morphine (2 mg, then 0.2 mg/h, n = 30), or patient-controlled analgesia (PCA) morphine only (n = 30). All patients received PCA morphine and res- cue morphine as necessary postoperatively. For the first 24 h, pain and sedation scores and respiratory, cardiovascular, and side effect measures were moni- tored. There was no significant difference in pain scores and PCA morphine use between tramadol and epidural morphine. Pain scores at rest and on coughing were lower in the Tramadol and Epidural Morphine groups than in the PCA Morphine group at various time points over the first 12 h. The Tramadol and Epi- dural Morphine groups used significantly less hourly PCA morphine than the PCA Morphine group at spe- cific time points in the first 10 h. Vital capacities in the Tramadol group were significantly closer to baseline values at the 20-h point than in the PCA Morphine group. We conclude that an intraoperative bolus of tra- madol followed by an infusion was as effective as epi- dural morphine and avoided the necessity of placing a thoracic epidural catheter. (Anesth Analg 2002;94:523–8) T ramadol hydrochloride is a synthetic opioid ag- onist analgesic acting at the  receptor (OP 3 ) (1). Its analgesic potency has been described as 5–10 times less than that of morphine, equal to that of meperidine (2) and to 0.001 that of fentanyl (3). Its analgesic efficacy lies between that of codeine and morphine. Tramadol is a racemic mixture of two en- antiomers with a structure similar to that of other opioid analgesics (4). However, only 30% of its effect can be antagonized by naloxone (2), and a significant portion of its action is mediated through non-opioid mechanisms, including monoamine modulation and synergy with opioid agonism (3,5). The opioid affinity, the inhibition of the uptake of norepinephrine and serotonin, and the further presynaptic release of sero- tonin (6) are dependent on the enantiomers, which have a complementary and synergistic antinociceptive effect (7). A previous trial comparing the analgesic efficacy and respiratory effects of different treatment regimens showed that a single tramadol bolus given at the end of surgery provided postoperative analgesia equiva- lent to that of continuous epidural morphine for the initial postoperative period (8). Arterial oxygen and carbon dioxide tensions were significantly better in the Tramadol group for the first 4 h postoperatively. Continued use of tramadol might extend these ob- served benefits further into the postoperative period. To investigate this possibility, we compared the anal- gesic efficacy produced by an IV tramadol infusion with that obtained with the use of an epidural mor- phine infusion, our current postoperative standard for thoracotomy patients, by using patient-controlled an- algesia (PCA) with IV morphine as a concomitant control. Methods Patients undergoing posterolateral thoracotomy for lung resection were recruited for this prospective, random- ized, double-blinded study. Appropriate informed con- sent was obtained according to the Treaty of Helsinki. Tramadol was supplied by Grunenthal GMBH, Aachen, Germany. Accepted for publication November 6, 2001. Address correspondence and reprint requests to Dr. R. A. Dyer, D23 Department of Anesthesia, New Groote Schuur Hospital, Anzio Road, Observatory, Cape Town, South Africa. Address e-mail to dyer@samiot.uct.ac.za. ©2002 by the International Anesthesia Research Society 0003-2999/02 Anesth Analg 2002;94:523–8 523