Respiratory and cardiovascular effects of buprenorphine in conscious rabbits.

Objective: To quantify the respiratory and cardiovascular effects of intravenous or subcutaneous buprenorphine in conscious rabbits.
Study Design: Prospective experimental trial.
Animals: Eight healthy, young adult New Zealand white rabbits (four female).
Methods: Rabbits were instrumented with intraabdominal arterial and venous catheters and diaphragmatic electromyographic electrodes 2 weeks before experiments. Arterial blood pressure, arterial blood gases, heart rate and respiratory rate were monitored during experiments. Buprenorphine (0.06 mg) was administered either intravenously or subcutaneously to conscious rabbits. Respiratory and cardiovascular parameters were compared to baseline at 10 and 22 minutes after intravenous buprenorphine administration, and at 30, 60, and 90 minutes after subcutaneous buprenorphine administration.
Results: Buprenorphine administration, at a dose of approximately 0.02 mg kg(-1), did not change blood pressure or heart rate. However, respiratory rate decreased from 252 +/- 26 to 39 +/- 26 breaths minute(-1) (mean +/- SD), and from 306 +/- 38 to 90 +/- 38 breaths minute(-1) following intravenous and subcutaneous administration of buprenorphine, respectively. Subsequent to intravenous and subcutaneous buprenorphine, arterial oxygen tension decreased from 88 +/- 4 to 72 +/- 4 mmHg (11.7 +/- 0.5 to 9.6 +/- 0.5 kPa) and from 87 +/- 3 to 77 +/- 3 mmHg (11.6 +/- 0.4 to 10.3 +/- 0.4 kPa), respectively. Buprenorphine, by either route of administration, increased arterial carbon dioxide tension from 36 to 41 mmHg (4.8-5.5 kPa) and increased the alveolar-arterial oxygen gradient from 15 to > or =20 mmHg (2 to > or =2.7 kPa).
Conclusions and Clinical Relevance: Buprenorphine administration decreased respiratory rate and produced mild hypoxemia in conscious rabbits. While these changes were well tolerated by healthy animals, caution should be exercised when administering buprenorphine to rabbits predisposed to respiratory depression.