Epidural and intravenous fentanyl infusions are clinically equivalent after knee surgery

The management of postoperative pain with continuous epidural fentanyl infusion was compared with continuous intravenous fentanyl infusion. In a randomized, doubleblind protocol we prospectively studied 20 patients undergoing repair of the anterior cruciate ligament of the knee. The quality of analgesia and the incidence of side effects were documented. Compared with patients receiving continuous intravenous fentanyl infusion, at 18 h postoperatively patients given continuous epidural fentanyl infusion reported similar pain scores both at rest (22 +/- 25 vs 27 +/- 21, P = 0.52) and with ambulation (59 +/- 18 vs 56 +/- 22, P = 0.82). Plasma fentanyl levels were 1.8 +/- 0.4 and 1.7 +/- 0.4 ng/mL (P = 0.91) for the intravenous and epidural groups, respectively. There were no significant differences in the incidence of nausea, pruritus, or urinary retention. There was no respiratory depression in either group. We conclude that when compared with continuous intravenous fentanyl infusion, continuous epidural fentanyl infusion offers no clinical advantages for the management of postoperative pain after knee surgery.