Comparison of epidural and patient-controlled intravenous morphine following joint replacement surgery

The authors conducted a randomized, prospective study comparing epidural morphine with patient-controlled intravenous (iv) morphine in 30 patients recovering from total hip or total knee arthroplasty. Six, 18, and 24 hr postoperatively, patients used a 10 cm visual-analogue scale to indicate both their current degree of discomfort and the maximum discomfort they had experienced since the previous evaluation. Pain at the time of evaluation did not differ between patients receiving epidural (2.6 +/- 0.4 cm, mean +/- SEM) and patient-controlled iv morphine (3.4 +/- 0.3 cm). However, patients who received epidural morphine recalled less pain during the period preceding evaluation (4.2 +/- 0.5 cm) than did those receiving patient-controlled analgesia (5.5 +/- 0.4 cm, P less than 0.05). Patients receiving epidural morphine were more likely to require treatment for pruritus (4 of 15) than patients who received patient-controlled iv morphine (none of 15, P less than 0.05). Minimum respiratory rates were lower in patients receiving epidural morphine (15.0 +/- 0.3) than in those receiving patient-controlled analgesia (16.5 +/- 0.4, P less than 0.05), but no patients required treatment for respiratory depression. The authors conclude that epidural morphine may provide more consistent analgesia following joint replacement surgery than patient-controlled morphine; however, there is a higher incidence of side-effects with the epidural technique.