Effects of buprenorphine on respiratory and cardiovascular functions during hypoxia in anaesthetized rabbits

Respiratory and cardiovascular variables were studied in 10 anaesthetized rabbits, before and after buprenorphine i.v. injections (cumulative doses of 5 to 100 micrograms/kg). In normoxic conditions, buprenorphine induced hypoventilation, due to a decrease in respiratory rate, and bradycardia: mean maximum modifications in ventilation (-17%) and heart rate (-7%) were obtained with buprenorphine 10 and 100 micrograms/kg, respectively. Isocapnic hypoxia, produced by the inhalation of a gas mixture containing 10% O2 in nitrogen for 5 min, provoked a mean 44% increase in base line ventilation and a mean 15% decrease in heart rate. The ventilatory response to hypoxia was not significantly modified by buprenorphine on an average; large decreases in hypoxic drive could still be observed in 3 out of 10 animals with buprenorphine 5 and 10 micrograms/kg. Buprenorphine enhanced hypoxia-induced bradycardia: a mean maximum decrease in heart rate (-29%) was reached with 10 micrograms/kg of this opioid.