Compared to etorphine-azaperone, the ketamine-butorphanol-medetomidine combination is also effective at immobilizing...

To compare immobilization efficacy of a nonpotent opioid drug combination, ketamine-butorphanol-medetomidine (KBM) to the preferred etorphine-azaperone (EA) combination in zebras.

Randomized crossover trial.

A group of ten adult zebra (six females and four male).

KBM and EA were administered once to the zebras in random order by dart, 3 weeks apart. Once a zebra was recumbent and instrumented, physiological parameters were measured and recorded at 5-minute intervals until 20 minutes. Antagonist drugs were administered at 25 minutes. KBM was antagonised using atipamezole (7.5 mg mg^-1 medetomidine dose) and naltrexone (2 mg mg^-1 butorphanol dose). EA was antagonized using naltrexone (20 mg mg^-1 etorphine dose). Induction and recovery (following antagonist administration) times were recorded. Physiological parameters, including invasive blood pressure and blood gas analysis, were compared between combinations using a general linear mixed model. Data are reported as mean ± standard deviation or median (interquartile range).

The doses of KBM and EA administered were 3.30 ± 0.18, 0.40 ± 0.02 and 0.16 ± 0.01 mg kg^-1; and 0.02 ± 0.001 and 0.20 ± 0.01 mg kg^-1, respectively. KBM and EA induction times were 420 (282-564) and 240 (204-294) seconds, respectively (p = 0.03). Zebras remained recumbent throughout the study procedures. Systolic blood pressure (226 ± 42 and 167 ± 42 mmHg) and oxygen partial pressure (64 ± 12 and 47 ± 13 mmHg) were higher for KBM compared to EA (p < 0.01). Recovery time, after administering antagonists, was 92 (34-1337) and 26 (22-32) seconds for KBM and EA, respectively (p = 0.03).

Compared to EA, KBM also immobilized zebras effectively. Systemic hypertension and moderate hypoxaemia are clinical concerns of KBM and severe hypoxaemia is a concern of EA. This occurrence of hypoxaemia highlights the importance of oxygen administration during immobilization.