Biochemical variables in free-ranging white-tailed deer (Odocoileus virginianus) after chemical immobilization in clover traps or via ground-darting

The objective of this prospective observational cohort study in free-ranging female white-tailed deer (Odocoileus virginianus) was to compare the physiologic effects of two methods of anesthetic drug administration: hand-injection in Clover traps and remote injection by dart after ground-stalking. Six trapped and 14 darted female deer were injected with a median (minimum, maximum) of 590 microg/kg butorphanol (401, 1070 microg/kg), plus 235 microg/kg medetomidine (160, 429 microg/kg) intramuscularly. In the trap, the deer struggled when approached and were restrained for injection. Darted deer sprinted away after injection. Once immobilized, deer were transported to a veterinary hospital where blood was collected and vital signs were measured on admission. Admission data from a subset of deer in which measurements were taken within 40 min of trapping (n = 6) or darting (n = 5) were analyzed. After salpingectomy under isoflurane and while still anesthetized, another blood sample was collected from all 20 deer. Body weight and immobilization drug doses were not different between groups. On admission, most deer from both groups were hypoxemic, although the darted deer were significantly more hypoxemic. The median rectal temperature in trapped deer was higher than in darted deer, and temperatures higher than 39 degrees C only occurred in trapped deer. The median heart rate in trapped deer was more than twice that in darted deer. Trapped deer had lower median pH and base excess; in trapped deer, the median plasma lactate concentration was more than fivefold higher than in darted deer. After surgery, the median serum creatine kinase concentration was nearly 10-fold higher in trapped deer, and the median cardiac troponin I concentration was higher in trapped deer but undetectable in 10 of 14 darted deer. The white-tailed deer immobilized by hand-injection in Clover traps experienced more severe physiologic perturbations than deer remotely injected by dart after ground-stalking. These perturbations might be sufficient to cause myocardial damage.