Anesthesia of polar bears using xylazine-zolazepam-tiletamine or zolazepam-tiletamine.

Immobilization features and physiologic effects of combinations of xylazine-zolazepam-tiletamine (XZT) and zolazepam-tiletamine (ZT or Telazol) were compared in nine captive and 17 free-ranging polar bears (Ursus maritimus) between 1998 and 2001. Although induction time was similar between drugs, induction dosage and volume were less with XZT. Induction of immobilization with XZT was predictable and smooth, muscle relaxation was good, and all bears remained completely immobilized and unresponsive to stimuli throughout a 1 hr handling period. The combination XZT was safely tolerated at two to three times the recommended dosage of 5 mg/kg (i.e., xylazine at 2 mg/kg + Telazol at 3 mg/kg). Bears immobilized with XZT had slower pulse rates, higher mean arterial pressures, and lower arterial oxygen tensions than bears immobilized with ZT. Rectal temperature increased slowly over time (approximately 0.5 C per hr) following immobilization with XZT. Based on response to a painful stimulus (compression of a claw bed), XZT was a more effective analgesic than ZT. Although the immobilization effects of XZT could not be reversed with the alpha 2-antagonist drug tolazoline, they were reversed with yohimbine or atipamezole. However, the time to complete reversal of effects (i.e., standing and ambulatory) was highly variable among bears.