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

Abstract

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 (% O2Sa) = 49 % + 16 (mean + SD) and PaO2 = 4.666 + 1.200 kPa (35 + 9 mm Hg)), hypercapnic (PaCO2 = 8.265 + 1.600 kPa (62 + 12 mm Hg)) and acidaemic (pHa = 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 % O2Sa and PaO2 increased while blood pHa and PaCO2 remained unchanged.Tracheal intubation via the nose is not difficult, and when oxygen is insufflated, the PaO2 and the % O2Sa 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.

Efficacy of a Portable Oxygen Concentrator with Pulsed Delivery for Treatment of Hypoxemia During Anesthesia of Wildlife

“…A mild to severe hypoxaemia was recorded in white rhinoceros (PaO 2 31-73 mmHg) but also in black rhinoceros (PaO 2 39-77 mmHg). Severe hypoxaemia has previously been reported in white rhinoceros immobilised with different opioid-based protocols (Bush et al, 2004;Hattingh et al, 1994), but this is the first study presenting arterial blood gases in free-ranging black rhinoceros, showing that severe hypoxaemia can occur in both species. P B = barometric pressure; P(A-a)O 2 = alveolar-arterial oxygen tension difference (at 37°C).…”

“…The higher tachycardia rates recorded initially in free-ranging white rhinoceros (130-156 bpm) compared to in the two boma-held white rhinoceros (110 bpm) probably reflects the contribution of physical exertion before recumbency. Bush et al (2004) reported that in white rhinoceros immobilised with lower doses of etorphine, heart rate was elevated despite alleviation of hypoxaemia through oxygen supplementation. Since these animals were hypercapnic, this may indicate that hypercapnia contributed more than hypoxaemia to the development of tachycardia.…”

“…However, methods of oxygen delivery and flow rates have been evaluated in only a few wildlife species (Bush et al, 2004;Dunlop et al, 1994;Heard et al, 1986;Mich et al, 2008;Read et al, 2001;Schumacher et al, 1997).…”

“…Adverse side effects during immobilisation of rhinoceros include hypoxaemia, acidosis, and hypertension (Bush et al, 2004;Hattingh et al, 1994;Heard et al, 1992). To improve respiration in immobilised rhinoceros, several drugs have been used, including nalorphine and nalbuphine and the respiratory stimulant doxapram (Hattingh et al, 1994;Kock, 1992;Kock & Morkel, 1993;Kock et al, 1995;Raath, 1999;Reuter & Winterbach, 1998).…”

Capture-related Hypoglycemia and Recovery in Free-ranging Black Rhinoceroses (Diceros bicornis bicornis)

“…Hypoglycemia can result in impaired thermoregulation and may predispose muscles and tendons to traumatic injury. In addition, the effect of potent narcotics and recumbency can exacerbate these problems by cardiorespiratory changes resulting in hypoxemia, hypercapnia, and inadequate tissue perfusion (Bush et al, 2004). Identifying serial changes in blood chemistry and electrolytes might determine potential interventions that can minimize complications.…”