RESUMO
OBJECTIVE: To determine the cardiovascular effects of buprenorphine in isoflurane- and halothane-anesthetized dogs. ANIMALS: 6 healthy adult hound-type dogs given buprenorphine (16 micrograms/kg of body weight, i.v.) or isovolumetric 5% dextrose solution during anesthesia with isoflurane or halothane. PROCEDURE: Each dog was anesthetized 4 times, with a minimum of 10 days between episodes. Anesthesia was induced with isoflurane or halothane in O2 by mask, and was maintained with 1.9% isoflurane or 1.3% halothane (end-tidal concentration). The PaCO2 was maintained between 35 and 45 mm of Hg by use of mechanical ventilation, and the following variables were determined: systolic, diastolic, and mean arterial blood pressures; cardiac output; cardiac index; stroke volume; heart rate; systemic vascular resistance; mean pulmonary arterial pressure; and pulmonary vascular resistance. In addition, arterial blood samples for gas and acid-base analyses were collected at 30-minute intervals for 2.5 hours. After baseline values were recorded, dogs were randomly assigned to receive either buprenorphine (16 micrograms/kg, i.v.) or isovolumetric 5% dextrose solution. All variables were then recorded at 15-minute intervals for 2.5 hours. RESULTS: During isoflurane anesthesia, buprenorphine administration caused significant (P < or = 0.05) reductions in diastolic arterial pressure, mean arterial pressure, systolic arterial pressure, cardiac index, and heart rate, whereas systemic vascular resistance increased significantly. During halothane anesthesia, buprenorphine administration caused significant decreases in heart rate, cardiac index, mean, systolic and diastolic arterial blood pressures, and stroke volume, whereas pulmonary arterial blood pressure and systemic vascular resistance increased significantly. CONCLUSION: Although the changes seen were significant, they were not sufficiently large to be of clinical importance in healthy dogs.