Ineffective analgesia after extradural tramadol hydrochloride in patients undergoing total knee replacement

Postoperative analgesia after two extradural tramadol regimens was compared with that obtained using a standard extradural morphine regimen in patients undergoing total knee replacement. Extradural anaesthesia with light general anaesthesia was used. Patients received extradurally either: tramadol 50 mg by bolus injection followed by infusion (5 mg.h-1 for 12 h and 2.5 mg.h-1 for a further 12 h) (group T50), tramadol 100 mg by bolus injection followed by infusion (10 mg.h-1 for 12 h and 5 mg.h-1 for a further 12 h) (group T100) or morphine sulphate 2 mg by bolus injection followed by infusion (0.2 mg.h-1 for 12 h and at 0.1 mg.h-1 for further 12 h) (group M). Analgesia was allocated according to a controlled double-blind design. Visual analogue pain scores were markedly poorer (p < 0.05) and patient-controlled analgesic consumption was significantly greater (p < 0.01) in the two tramadol groups when compared with the morphine group. The study was discontinued after recruitment of 12 patients, as analgesia was deemed inadequate in those receiving tramadol extradurally. However, further study of this drug may be warranted to examine its effectiveness where postoperative pain is expected to be less severe, and to assess the effect of larger extradural doses and of co-administration of tramadol and morphine by this route.