Constant i.v. infusions of nalbuphine or buprenorphine for pain after abdominal surgery.

A double-blind, sex-stratified, study compared the analgesic efficacy and side effects of nalbuphine 10 mg ml-1 (group N) and buprenorphine 0.15 mg ml-1 (group B) administered as a continuous infusion (0.2 ml kg-1/24 h), after abdominal surgery. Patients could request additional i.m. analgesic for pain. The study groups were well matched. The trial was stopped after 55 patients had been studied (nalbuphine 29, buprenorphine 26), because nine patients in the nalbuphine group had inadequate pain relief (P less than 0.01) shortly after surgery (mean 2.5 h). Analysis of the results on an "intention to treat" basis showed that the patients who received buprenorphine had significantly greater pain relief at 1, 3, 6 and 20 h after surgery. Patients who received buprenorphine were assessed by the physiotherapist to have less pain and better chest expansion. More additional analgesic was given to the patients receiving nalbuphine. In the patients receiving buprenorphine, the mean ventilatory rate was less (N = 19 b.p.m., B = 14 b.p.m.) (P less than 0.001) and the increase in PaCO2 was greater (N = 0.5 kPa, B = 1.1 kPa) (P less than 0.001), compared with the value before operation. Side effects were equal, and no serious adverse effects were observed in either group.