Butorphanol with oxygen insufflation improves cardiorespiratory function in field-immobilised white rhinoceros ( Ceratotherium simum )

Opioid-induced immobilisation results in severe respiratory compromise in the white rhinoceros (Ceratotherium simum). The effectiveness of oxygen insufflation combined with butorphanol in alleviating respiratory depression in free-ranging chemically immobilised white rhinoceroses was investigated. In this prospective intervention study 14 free-ranging white rhinoceroses were immobilised with a combination of etorphine, azaperone and hyaluronidase. Six minutes (min) after the animals became recumbent, intravenous butorphanol was administered and oxygen insufflation was initiated. Previous boma trial results were used for comparison, using repeated measures two-way analysis of variance. The initial immobilisation-induced hypoxaemia in free-ranging rhinoceroses (arterial partial pressure of oxygen [PaO2] 35.4 mmHg +/- 6.6 mmHg) was similar to that observed in boma-confined rhinoceroses (PaO2 31 mmHg +/- 6 mmHg, n = 8). Although the initial hypercapnia (PaCO2 63.0 mmHg +/- 7.5 mmHg) was not as severe as that in animals in the boma trial (79 mmHg +/- 7 mmHg), the field-immobilised rhinoceroses were more acidaemic (pH 7.10 +/- 0.14) at the beginning of the immobilisation compared with boma-immobilised rhinoceroses (pH 7.28 +/- 0.04). Compared with pre-intervention values, butorphanol with oxygen insufflation improved the PaO2 (81.2 mmHg +/- 23.7 mmHg, p < 0.001, 5 min vs 20 min), arterial partial pressure of carbon dioxide (55.3 mmHg +/- 5.2 mmHg, p < 0.01, 5 min vs 20 min), pH (7.17 +/- 0.11, p < 0.001, 5 min vs 20 min), heart rate (78 breaths/min +/- 20 breaths/min, p < 0.001, 5 min vs 20 min) and mean arterial blood pressure (105 mmHg +/- 14 mmHg, p < 0.01, 5 min vs 20 min). Oxygen insufflation combined with a single intravenous dose of butorphanol improved oxygenation and reduced hypercapnia and acidaemia in immobilised free-ranging white rhinoceroses.