Combinations of Telazol®/medetomidine, Telazol®/xylazine, medetomidine/ketamine and ketamine/xylazine are commonly used for immobilizing cervids, but are not completely reversible and may result in prolonged recovery times.1,3,7,11 Telazol®/xylazine and ketamine/xylazine can also be associated with prolonged time to recumbency.3,11 Carfentanil/xylazine and etorphine/xylazine are reversible combinations successfully used in cervid species, but these protocols may cause hypoventilation and hypoxia.2,5,8 Fallow deer in particular are difficult to immobilize.4-6,9 The anesthetic protocol described here achieves quick and reversible induction via small drug volumes, while maintaining good cardiovascular function through combination of a pure opioid agonist with a partial antagonist. Such competitive mixtures deserve more careful study to better understand the pharmacology and physiology of their actions, but preliminary trials appear promising.
Sixty-three captive adult free-ranging fallow deer (Dama dama) were immobilized at the Fossil Rim Wildlife Center between January 1998 and April 2005. Forty-seven were captured for movement to another area, 12 for examination, and four for removal of debris from antlers. They were darted i.m. with a combination of carfentanil (average dose = 2.9 µg/kg; Wildlife Pharmaceuticals Inc., Fort Collins, Colorado 80524, USA), xylazine (average dose = 0.25 mg/kg; Xyla-Ject®, Phoenix Scientific, Inc., St. Joseph, Missouri 64503, USA) and butorphanol (average dose = 36.8 µg/kg; Torbugesic®, Fort Dodge Animal Health, Fort Dodge, Iowa 50501, USA). Anesthetic effects were reversed using yohimbine (average dose = 0.23 mg/kg i.m.; Wildlife Pharmaceuticals Inc.) and naltrexone (50 mg per animal, 1/2 i.v., 1/2 i.m.; Wildlife Pharmaceuticals Inc.). The average time from injection to initial effect was 3.53 min. The average time from injection to recumbency was 5.56 min. Following naltrexone administration, the average time to first sign of arousal was 1.89 min, and 2.97 min to standing.
Seven individuals received ketamine to assist in handling when anesthesia was “light” or when painful procedures were performed. One deer was intubated and placed on isoflorane for eyelid mass removal. Butorphanol partially reverses the effects of carfentanil, specifically the respiratory depression. Respiratory depression (defined as respiratory rate <12 breaths per min or episodes of apnea) was seen in 16 deer and may be attributable to the effects of xylazine10,12 or inadequate antagonism by butorphanol. When respiratory depression was severe enough to cause episodes of apnea, the yohimbine reversal dose was given before the end of the procedure, usually resulting in an increased respiratory rate.
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