Endocrine and Hemodynamic Effects of Antagonism of Fentanyl-Induced Respiratory Depression by Nalbuphine

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Abstract
Endocrine and hemodynamic changes associated with the antagonism of fentanyl by nalbuphine have not been reported. Therefore, the authors studied ten patients after anesthetic induction with thiopental, fentanyl, trachea] intubation aided by sucdnylcholine and maintenance with diazepam, pancuronium, N2O, and further doses of fentanyl. Eight of the patients underwent cholecystectomy, one had a hysterectomy, and another had an abdominoplasty. After reversal of neuromuscular block at the conclusion of surgery, normal ventilation was restored by 0.22 ± 0.02 mg/kg intravenous nalbuphine (mean ± SEM). Plasma levels of free norepinephrine, histamine, and cortisol did not increase after antagonism of the fentarnyl-induced respiratory depression, but plasma coticentration of epinephrine increased significantly but without significant hemodynamic changes. Minute ventilation was 1.5 ± 0.4 L/min before and 11 ± 1, 10 ± 1, 11 ± 1, and 10 ± 1 L/min at 15, 30, 45, and 60 min after antagonism; corresponding PaCO2 levels were 56 ± 2, 44 ± 1, 49 ± 7, 49 ± 1, 42 ± 1 mm Hg. The mean analogue pain score remained below 1.5. We conclude that nalbuphine effectively antagonizes fentanyl-induced respiratory depression without adverse endocrine and circulatory changes or loss of analgesia.