Corticoadrenal and Cardiorespiratory Responses to Administration of Propofol Combined with Dexmedetomidine or Ketamine in Rabbits.

Anesthetic protocols may influence adrenal function. Effective methods for modulating stress are desirable to minimize secondary effects during the perioperative period. The aim of this study was to evaluate the effects of the administration of propofol with dexmedetomidine or ketamine on corticoadrenal function and heart and respiratory rates. A random treatment-order design was used: each rabbit received all treatments, with at least 14 d between experiments. Rabbits were assigned to 3 treatment groups (10 per group): group 1, 1 mL normal saline solution intravenously; group 2, propofol (3 mg/kg IV) and dexmedetomidine (0.35 mg/kg IM); and group 3, propofol (3 mg/kg IV) and ketamine (1 mg/kg IV). Dexmedetomidine was injected 15 min prior to propofol administration. Blood samples were obtained before drug administration and at 5, 10, 30, and 60 min and 24 h after injection. Serum cortisol and corticosterone levels were measured by competitive enzyme immunoassay. Serum glucocorticoid concentrations did not change in group 2. However, rabbits in group 3 showed an increase in serum cortisol (at 5-60 min) and corticosterone (at 5-120 min) when compared with all other groups at the corresponding time points. This increase probably reflected both propofol- and ketamine-associated stimulatory effects corticoadrenal function. Respiratory rate decreased in groups 2 and 3 animals, and heart rate decreased in group 2, probably due to sympathetic inhibition by propofol and dexmedetomidine. In conclusion, propofol-ketamine provides suitable cardiorespiratory stability in rabbits but enhances glucocorticoid secretion more than dexmedetomidine-propofol anesthesia. Glucocorticoid levels in anesthetized rabbits should be considered during protocol design to minimize the stress response to surgery and to avoid erroneous data interpretation.