Evaluation of detomidine anesthetic combinations in the rabbit
1994
Hurley, R.J. | Marini, R.P. | Avison, D.L. | Murphy, J.C. | Olin, J.M. | Lipman, N.S.
Detomidine, a potent alpha 2-adrenergic receptor agonist, was chosen for study alone and in combination with ketamine with or without diazepam. Four regimens were evaluated: detomidine (150 microgram/kg of body weight) alone (D); ketamine (35 mg/kg) and detomidine (150 microgram/kg) (KD); ketamine (35 mg/kg) and high-dose detomidine (300 microgram/kg)(KDh); and ketamine (35 mg/kg), diazepam (1 mg/kg), and detomidine (150 microgram/kg)(KDD). The same six rabbits were anesthetized with each combination at weekly intervals. Atropine (0.04 mg/kg) was administered as a preanesthetic 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 blood gas tensions were measured. Pedal, palpebral, and righting reflexes also were evaluated. Cardiopulmonary depression, as indicated by decrease in heart and respiratory rates, blood pH, PO2, and increase in PCO2, was observed in all groups. With the exception of heart rate, detomidine used alone caused the least depression of these parameters. Reflexes were consistently lost only after KDh and KDD administrations. The pedal reflex, used as an index of anesthetic depth, was lost in response to KDh and KDD for 56.7 +/-11.6 and 43.8 +/-7.4 min, respectively (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, these combinations were not considered safe or reliable. The KDD regimen did not have any advantages over other established injectable anesthetic regimens and, until the cause of the myocardial injury can be determined, this combination should also be avoided.
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