Cardiorespiratory effects of medetomidine and dexmedetomidine combined with tiletamine-zolazepam for the immobilization of Asiatic black bears (Ursus thibetanus) under isoflurane general anesthesia

The aim of this paper was to compare the cardiorespiratory effects of the two combinations (medetomidine-tiletamine-zolazepam (MTZ) or dexmedetomidine-tiletamine-zolazepam (DTZ)) used for Asiatic black bear (Ursus thibetanus) immobilization. A retrospective analysis was carried out, reviewing the anesthetic records of captive bears. Sixty-six records were reviewed. The bears were immobilized, and general anesthesia was maintained with isoflurane vaporized in 100% oxygen. The mean sedation time and score were evaluated. The cardiorespiratory parameters were recorded every 10 minutes from intubation until extubation. Mean sedation time was 26.1 ± 14.5 minutes for the MTZ group and 25.6 ± 19.4 minutes for the DTZ group. The heart rate and the respiratory rate were higher in the bears immobilized with DTZ (66 ± 19 beats/min; 13 ± 5.2 breaths/min) as compared with the bears immobilized with MTZ (57 ± 14.5 beats/min; 10 ± 4.7 breaths/min) whereas the mean arterial pressure did not differ significantly between the groups. The body temperature was in the normal range throughout the procedures in all bears (MTZ 36.3 ± 0.9°C; DTZ 37 ± 1°C). In conclusion, the two protocols used in this study have been proven to be safe and reliable for the immobilization of Asiatic black bears, and the DTZ combination seemed to be associated with less cardiorespiratory depression than the MTZ one.