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

Abstract

Improvement of chemical capture is an important part of wildlife conservation and animal welfare to minimise distress for the animals and the risk of morbidity and mortality. The aim of this thesis was to improve wildlife immobilisation and anaesthesia by studying physiological variables and clinically evaluate different drug combinations and methods of capture in selected species. Reversible anaesthetic protocols were developed for use in free-ranging lions and four species of SouthEast Asian primates. Capture and anaesthesia of free-ranging wolverines, brown bears, black and white rhinoceros were physiologically evaluated. The effect of intranasal oxygen supplementation on arterial oxygenation was assessed in brown bears and rhinoceros. Partial reversal of the opioid effect and different body positions were evaluated in rhinoceros.Capture methods used included darting from a helicopter or the ground, and physical restraint followed by drug injection. Medetomidine-ketamine was used in wolverines and medetomidine-zolazepam-tiletamine in primates, lions and brown bears. Rhinoceros were immobilised with a combination of an opioid, azaperone and an alpha 2 -agonist. Body temperature and cardiorespiratory variables were monitored in all animals. Arterial blood samples were analysed to interpret pulmonary gas exchange and acid-base status in carnivores and rhinoceros.Low doses of medetomidine-zolazepam-tiletamine rapidly anaesthetised primates and lions, and reversal with atipamezole resulted in a smooth and calm recovery. Physiological alterations varied with different protocols and species and included changes in body temperature, respiratory and heart rates, gas exchange and acid-base balance. Hypoxaemia was recorded in all rhinoceros and most carnivore species. The major contributor to hypoxaemia was likely ventilation-perfusion mismatch including shunt. In rhinoceros, hypoventilation contributed to an impaired gas exchange and the animals remained hypoxaemic despite partial reversal. However, in black rhinoceros arterial oxygenation was higher during sternal compared to lateral recumbency. Capture-induced lactic acidaemia was recorded in carnivores and rhinoceros. Intranasal oxygen supplementation improved arterial oxygenation.In conclusion, this thesis increases the understanding of the effects of capture and anaesthesia in several wildlife species. Physiological derangements were identified, potential causative factors were investigated and methods for improvement were evaluated.

OXYGEN SUPPLEMENTATION IN ANESTHETIZED BROWN BEARS (URSUS ARCTOS)—HOW LOW CAN YOU GO?

“…Thereafter, the flow rate was adjusted based on body mass to approach the minimum required flow rate necessary to meet a target PaO 2 . Calculation of the target PaO 2 has been described (Fahlman et al 2012). The target PaO 2 represents the estimated PaO 2 value that could be expected in a …”

“…Most physiologic studies that include blood gas analysis demonstrate hypoxemia with the drugs and doses used for anesthesia in free-ranging and captive wild animals (Read 2003;Mich et al 2008;Fahlman et al 2012). Mild to marked hypoxemia has been documented in free-ranging and captive brown bears (Ursus arctos) anesthetized with medetomidine-zolazepamtiletamine (MZT; Fahlman et al 2011).…”

“…Intranasal oxygen supplementation is a simple and efficient method to increase arterial oxygenation, as documented in some wildlife species (Cattet et al 2003;Fahlman et al 2010Fahlman et al , 2012. In brown bears, the use of intranasal oxygen at flow rates as high as 6-10 L/min has been reported (Mortenson and Bechert 2001;Cattet et al 2003).…”

“…Oxygen sources used in the field include oxygen cylinders that store gaseous oxygen under high pressure and portable batterydriven oxygen concentrators that extract nitrogen from the air and produce oxygen on site (Fahlman et al 2010(Fahlman et al , 2012. Small light-weight oxygen cylinders are easy to carry during fieldwork, but refilling cylinders may entail complex logistics in remote areas.…”

LOW FLOW OXYGEN THERAPY FROM A PORTABLE OXYGEN CONCENTRATOR OR AN OXYGEN CYLINDER EFFECTIVELY TREATS HYPOXEMIA IN ANESTHETIZED WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS)

“…As an alternative, the assumed normal partial pressure of arterial oxygen (PaO 2 ) value that could be expected in a fully conscious animal can be estimated by calculation of the target PaO 2 , as previously described. 5 Intranasal oxygen administered at very low flow rates (0.5-3 L/min; 5-40 ml/kg) improved the PaO 2 in hypoxemic wild brown bears (Ursus arctos) 4 and domestic dogs. 7 In comparison, higher flow rates have been recommended for use in dogs (50-200 ml/kg per minute).…”