EVALUATION OF DETOMIDINE ANESTHETIC COMBINATIONS IN THE RABBIT

Detomidine, a potent alpha(2)-adrenergic receptor agonist, was chosen for study alone and in combination with ketamine with or without diaze pam. Four regimens were evaluated: detomidine (150 mu g/kg of body wei ght) alone (D); ketamine (35 mg/kg) and detomidine (150 mu g/kg) (KD); ketamine (35 mg/kg) and high dose detomidine (300 mu g/kg)) (KDh); an d ketamine (35 mg/kg), diazepam (1 mg/kg), and detomidine (150 mu g/kg ) (KDD). The same six rabbits were anesthetized with each combination at weekly intervals. Atropine (0.04 mg/kg) was administered as a prean esthetic 5 min prior to test substance administration All agents were administered IM, except for diazepam, which was administered IV. Heart and respiratory rates, mean arterial blood pressure, and arterial blo od gas tensions were measured. Pedal, palpebral, and righting reflexes also were evaluated. Cardiopulmonary depression, as indicated by decr ease in heart and respiratory rates, blood pH, PO2, and increase in PC O2, was observed in all groups. With the exception of heart rate, deto midine used alone caused the least depression of these parameters. Ref lexes were consistently lost only after KDh and KDD administrations. T he pedal reflex, used as an index of anesthetic depth, was lost in res ponse to KDh and KDD for 56.7 +/- 11.6 and 43.8 +/- 7.4 min, respectiv ely (mean +/- SEM). Three of the six rabbits were anorectic after KDh administration. Necropsy and histologic evaluation revealed myocardial necrosis and fibrosis in five animals. Due to the inconsistent reflex loss in response to KD and D and inappetance associated with KDh, the se combinations were not considered safe or reliable. The KDD regimen did not have ally advantages over other established injectable anesthe tic regimens and, until the cause of the myocardial injury can be dete rmined, this combination should also be avoided.