Oral Presentation 64th International Conference of the Wildlife Disease Association 2015

Butorphanol with oxygen insufflation corrects etorphine-induced hypoxaemia in chemically immobilized white rhinoceros (Ceratotherium simum) (#33)

Anna Haw 1 , Leith Meyer 2 , Andrea Fuller 1 , Peter Buss 3 , Michele Miller 4 , Markus Hofmeyr 3
  1. Brain Function Research Group, University of the Witwatersrand, Johannesburg, South Africa
  2. Paraclinical Sciences, University of Pretoria, Pretoria
  3. Veterinary Wildlife Services, South African National Parks, Skukuza
  4. Stellenbosch University, Stellenbosch

Conservation and management of rhinoceros species relies heavily on the ability to safely immobilize these large pachyderms. However, white rhinoceros immobilized with potent opioids experience adverse physiological changes including severe hypoxaemia, hypercapnia and acidosis. We evaluated the efficacy of butorphanol and oxygen in alleviating opioid-induced respiratory depression in boma-managed rhinoceros. Eight sub-adult male white rhinoceros were captured in Kruger National Park and housed in bomas for the duration of the experiment. Each rhinoceros was immobilized on four occasions at two-week intervals such that all animals received the same treatments in a randomized order. The treatments comprised intravenous butorphanol, oxygen insufflation, butorphanol combined with oxygen and a control. Non-invasive cardiorespiratory measurements and arterial blood gas samples were taken at 5 min intervals during the immobilization. Chemical immobilization with etorphine, azaperone and hyaluronidase, as per standard procedure for the white rhinoceros, caused severe hypoxaemia (PaO2 = 27 ± 7 mmHg), hypercapnia (PaCO2 = 82 ± 6 mmHg) and acidosis (pH = 7.26 ± 0.02) 5 min after initial recumbency. Compared to pre-intervention values, butorphanol administration (without oxygen) improved the PaO2 (60 ± 3 mmHg, p < 0.001), PaCO2  (67 ± 4 mmHg, p < 0.001) and pH (7.31 ± 0.06, p < 0.001), while oxygen insufflation alone exacerbated the hypercapnia (123 ± 20 mmHg, p < 0.001) and acidosis (7.12 ± 0.07, p < 0.001). Surprisingly, butorphanol combined with oxygen fully corrected the opioid-induced hypoxaemia (PaO2 = 155 ± 53 mmHg) and reduced the hypercapnia compared to the control trial. Oxygen insufflation combined with an intravenous dose of butorphanol was the only treatment that significantly improved the immobilization quality of boma-managed white rhinoceros by fully correcting the opioid-induced hypoxaemia. This supportive treatment (butorphanol+oxygen) should therefore be used during all white rhinoceros immobilizations to reduce the risk of capture-related morbidity and mortality.