Immobilization quality and cardiopulmonary effects of etorphine alone compared with etorphine–azaperone in blesbok (Damaliscus pygargus phillipsi)

Objective To evaluate the immobilization quality and cardiopulmonary effects of etorphine alone compared with etorphine-azaperone in blesbok (Damaliscus pygargusphillipsi). Study design Blinded, randomized, crossover design. Animals A total of 12 boma-habituated female blesbok weighing [mean ± standard deviation (SD)] 57.5 ± 2.5 kg. Methods Each animal was administered etorphine (0.09 mg kg-1) or etorphine-azaperone combination (0.09 mg kg-1; 0.35 mg kg-1) intramuscularly with a 1-week intertreatment washout period. Time to first sign of altered state of consciousness and immobilization time were recorded. Physiological variables were recorded, and arterial blood samples taken during a 40-minute immobilization period, after which, naltrexone (mean ± SD: 1.83 ± 0.06 mg kg-1) was intravenously administered. Recovery times were documented, and induction, immobilization and recovery were subjectively scored. Statistical analyses were performed. p < 0.05 was significant. Results No difference in time to first sign, immobilization time, and recovery times were observed between treatments. Time to head up was longer with etorphine-azaperone (0.5 ± 0.2 versus 0.4 ± 0.2 minutes; p = 0.015). Etorphine caused higher arterial blood pressures (mean: 131 ± 17 versus 110 ± 11 mmHg, p < 0.0001), pH, rectal temperature, arterial oxygen partial pressure (59.2 ± 7.7 versus 42.2 ± 9.8 mmHg), but lower heart (p = 0.002) and respiratory rates (p = 0.01). Etorphine-azaperone combination led to greater impairment of ventilatory function, with higher end-tidal carbon dioxide (p < 0.0001) and arterial partial pressure of carbon dioxide (58.0 ± 4.5; 48.1 ± 5.1 mmHg). Immobilization quality was greater with etorphine-azaperone compared to etorphine alone, median scores were 4 and 3, respectively (p < 0.0001). Conclusions and clinical relevance Both treatments provided satisfactory immobilization of blesbok, but in addition to a deeper level of immobilization, etorphine-azaperone caused greater ventilatory impairment. Therefore, with both protocols, oxygen supplementation is recommended.