Severe hypoxaemia in field-anaesthetised white rhinoceros (Ceratotherium simum) and effects of using tracheal insufflation of oxygen

White rhinoceros anaesthetised with etorphine and azaperone combination develop adverse physiological changes including hypoxia, hypercapnia, acidosis, tachycardia. and hypertension. These changes are more marked in field-anaesthetised rhinoceros. This study was designed to develop a technique to improve safety for field-anaesthetised white rhinoceros by tracheal intubation and oxygen insufflation. Twenty-five free-ranging white rhinoceros were anaesthetised with an etorphine and azaperone combination for translocation or placing microchips in their horns. Once anaesthetised the rhinoceros were monitored prior to crating for transportation or during microchip placement. Physiological measurements included heart and respiratory rate, blood pressure and arterial blood gas samples. Eighteen rhinoceros were intubated using an equine nasogastric tube passed nasally into the trachea and monitored before and after tracheal insufflation with oxygen. Seven rhinoceros were not intubated or insufflated with oxygen and served as controls. All anaesthetised rhinoceros were initially hypoxaemic (percentage arterial haemoglobin oxygen saturation (%O₂S_a) = 49 % ± 16 (mean ± SD) and P_aO₂ = 4.666 ± 1.200 kPa (35 ± 9 mm Hg)), hypercapnic (P_aCO₂ = 8.265 ± 1.600 kPa (62 ± 12 mm Hg)) and acidaemic (pH_a = 7.171 ± 0.073). Base excess was -6.7 ± 3.9 mmol/l, indicating a mild to moderate metabolic acidosis. The rhinoceros were also hypertensive (systolic blood pressure = 21.861 ± 5.465 kPa (164 ± 41 mm Hg)) and tachycardic (HR = 107 ± 31/min). Following nasal tracheal intubation and insufflation, the % O₂S_a and P_aO₂ increased while blood pH_a and P_aCO₂ remained unchanged. Tracheal intubation via the nose is not difficult, and when oxygen is insufflated, the P_aO₂ and the % O₂S_a increases, markedly improving the safety of anaesthesia, but this technique does not correct the hypercapnoea or acidosis. After regaining their feet following reversal of the anaesthesia, the animals' blood gas values return towards normality.