Patient-controlled epidural versus intravenous pethidine to supplement epidural bupivacaine after abdominal aortic surgery.

In a double-blind, randomized, crossover study of 25 patients after abdominal aortic surgery, we compared patient-controlled analgesia (PCA) with epidural versus intravenous pethidine. All patients received continuous epidural infusions of 0.125% bupivacaine adjusted to maintain appropriate sensory levels. The 48 hour study period commenced 36 to 48 hours after surgery and covered postoperative days 2 and 3. There was a crossover in PCA mode (epidural or intravenous) after 24 hours. Plasma pethidine concentration at the end of each 24 hour period and the total 24 hour pethidine dose did not change significantly between postoperative days 2 and 3. Pethidine plasma concentration was lower after 24 hours epidural than after intravenous PCA [125 (SD 108) ng/ml versus 171 (SD 107) ng/ml, P = 0.03], although pethidine dose did not differ significantly [mean 147 (SD 124) mg/24 h]. Visual analog pain scores (VAS) did not differ significantly between postoperative days 2 and 3, or at rest between epidural and i.v. groups. However, VAS with coughing and with abdominal palpation were lower in the epidural PCA group (P = 0.05, 0.008). With a background epidural infusion of 0.125% bupivacaine, PCA with epidural pethidine provided better pain control than PCA intravenous pethidine and this was achieved at lower plasma pethidine concentrations.