Patient-controlled analgesia with nalbuphine, a new narcotic agonist-antagonist, for the treatment of postoperative pain.

Patient-controlled analgesia (PCA, intravenous self-application of narcotics) has been studied during the early postoperative period in 40 ASA I-III patients recovering from elective major and minor surgery (20 abdominal and 20 orthopaedic operations). Doses of 3.7 mg of the new agonist-antagonist opioid analgesic nalbuphine were available on demand, whenever the patients felt that pain relief was necessary, delivered by a microprocessor-controlled injection pump (On-Demand Analgesia Computer, ODAC) in response to use of a patient-controlled manual switch. The maximum dose/h was set at 28.2 mg, with a refractory time of 1 minute between successful demands. A continuous nalbuphine infusion (0.44 mg X h-1) was administered in addition in order to prevent obstruction of the catheter. The duration of the PCA period was 17.9 (0.4-28.0) h (median, range). During that time, 13.3 (1-45) demands per patient were recorded, resulting in median individual nalbuphine consumptions of 51.3 (8.1-1050.5) micrograms X kg-1 X h-1. Self-administration was characterized by considerable intra- and inter-individual variability. Following abdominal surgery significantly more nalbuphine was needed compared to orthopaedic patients, but it resulted in poorer pain relief. There were no statistically significant differences in drug requirements or pain scores between the sexes. Overall efficacy and patient acceptance proved to be good. When compared with previous conventional postoperative analgesia, the effectiveness of PCA was judged superior by about 57% of patients. Side effects (nausea, sweating) occurred in about 10% of patients but were usually of minor intensity. No serious circulatory or respiratory problems were observed during the period of PCA. Patient-controlled analgesia is a promising technique for the treatment of acute pain and for clinical pain research.