Bispectral Index Analysis of Opioid Immobilization of Rocky Mountain Elk

Abstract: We immobilized elk with either isoflurane to produce general anesthesia (control), 0.01 mg/kg carfentanil plus 0.1 mg/kg xylazine, or 0.25 mg/kg butorphanol plus 0.4 mg/kg azaperone plus 0.15 mg/kg medetomidine (BAM) and measured the bispectral index (BIS). The carfentanil-xylazine BIS (70.4 + 1.4) and the BAM BIS (60.2 + 1.5) were higher than the control BIS (47.2 + 4.1; P ≤ 0.001). These data indicate that opioids produce neuroleptanalgesia and not general anesthesia or sedation, which explains observed elk responses to these drugs.