Influence of perioperative nalbuphine and fentanyl on postoperative respiration and analgesia.

In a double-blind study the relative postoperative respiratory and analgesic effects of perioperatively administered nalbuphine and fentanyl were compared in 60 females undergoing gynecological surgery under i.v. anesthesia. One milliliter (10 mg) nalbuphine was considered equipotent to 1 ml (100 micrograms) fentanyl. In the recovery period pain was assessed by visual analog score (VAS) and recovery by Pegboard scoring. Respiratory function was evaluated by continuous monitoring of respiratory frequency and end-tidal CO2 (ETCO2) and by frequent arterial blood gas analyses. The total volume of analgesic required for surgical analgesia was similar in the two groups. Patients in the nalbuphine group showed mild to moderate increases in pulse rate during the intubation phase and in blood pressure during surgery. Fentanyl was more effective in suppressing these cardiovascular responses. Within the first 15 min following recovery, increasing PaCO2 and ETCO2 as well as respiratory rates below 10/min were noted in 8 patients, who all belonged to the fentanyl group; in 4 of these patients i.v. naloxone had to be administered to reverse respiratory depression. Prolonged sedation was a common feature in patients receiving nalbuphine. It was concluded that fentanyl was superior to nalbuphine in attenuating the pressor responses to intubation and surgery. However, fentanyl was associated with respiratory depression in a considerable number of patients. The quality and duration of postoperative analgesia were similar in the two groups.