Abstract:
African wildlife species are increasingly being immobilised with combinations of a low dose of potent opioids combined with
medetomidine and azaperone. The physiological effects of these combinations in comparison to conventional potent opioidazaperone
combinations have scarcely been evaluated. In this cross-over study conducted on eight captive blesbok, we compared
the physiological variables of blesbok immobilised with 2 mg of thiafentanil + 10 mg of azaperone (TA); 0.5 mg thiafentanil +
1.5 mg medetomidine (TM), and 0.5 mg thiafentanil + 1.5. mg medetomidine + 10 mg azaperone (TMA). Thiafentanil’s effects
were antagonised with naltrexone at 10 mg naltrexone per mg thiafentanil, and the medetomidine effects with atipamezole at
5 mg atipamezole per mg medetomidine. The physiological variables were compared between treatment groups using descriptive
statistics and repeated measures ANOVA. The TA combination resulted in the shortest induction and recovery times, higher heart
rates, respiratory rates, PaO2, SpO2, and lower MAP and A-a gradients, but with less muscle relaxation. The TM and TMA combinations
caused marked bradycardia and hypoxaemia. The hypoxaemia was most severe in animals immobilised with TMA, and four of eight
blesbok immobilised had a PaO2 < 35 mmHg at the 10- or 15-minute sampling point. These blesbok were provided supplementary
oxygen, which corrected the hypoxaemia. The TA combinations caused the lowest degree of physiological compromise. All three
combinations were effective for the immobilisation of blesbok, but as the low-dose thiafentanil and high-dose medetomidine
combinations caused marked hypoxaemia, supplementary oxygen is recommended when using these combinations.
