Effects of Dexmedetomidine and Ketamine-Dexmedetomidine with and without Buprenorphine on Corticoadrenal Function in Rabbits.

Anesthetics may influence adrenal function and consequently alter serum glucocorticoid concentrations, leading to erroneous interpretations of results from anesthetized rabbits. However, decreases in glucocorticoid concentrations may be advantageous in protocols designed to minimize the stress response to surgery. This study characterized the variations in adrenocortical function based on changes in corticosterone and cortisol levels after various doses and combinations of dexmedetomidine, ketamine, and buprenorphine. Each rabbit received all treatments with a minimal interexperiment interval of 10 d. Rabbits were allocated to 7 groups (n = 10 per group) and received either 1 mL saline solution; dexmedetomidine at 0.05, 0.15, or 0.25 mg/kg; ketamine (35 mg/kg) and dexmedetomidine (0.25 mg/kg) without or with buprenorphine (0.03 mg/kg); or ketamine (35 mg/kg) and buprenorphine (0.03 mg/kg). Blood was sampled before drug administration and at 10, 30, 60, and 120 min and 24 h afterward. Serum glucocorticoid levels fell in all treatment groups except the one receiving ketamine-dexmedetomidine; in that group, serum glucocorticoids increased. Rabbits that received ketamine-dexmedetomidine-buprenorphine had the lowest serum glucocorticoid levels overall. In conclusion, dexmedetomidine reduces glucocorticoid secretion in rabbits but, when combined with ketamine, increases corticosterone and cortisol levels as well as heart and respiratory rates. The addition of buprenorphine to the ketamine-dexmedetomidine mixture reduces serum glucocorticoid levels. The influence of anesthetic drugs should be considered when designing a protocol to minimize the glucocorticoid response to surgery or when measuring glucocorticoid levels in rabbits.