Short Communication

Muscle tremors observed in white rhinoceroses immobilised with either etorphine–azaperone or etorphine–midazolam: An initial study

Mary Nasr, Leith C.R. Meyer, Peter Buss, María C. Fàbregas, Robin D. Gleed, Jordyn M. Boesch, Friederike Pohlin
Journal of the South African Veterinary Association | Vol 92 | a2142 | DOI: https://doi.org/10.4102/jsava.v92i0.2142 | © 2021 Mary Nasr, Leith C.R. Meyer, Peter Buss, Maria C. Fàbregas, Robin D. Gleed, Jordyn M. Boesch, Friederike Pohlin | This work is licensed under CC Attribution 4.0
Submitted: 09 January 2021 | Published: 28 June 2021

About the author(s)

Mary Nasr, Oradell Animal Hospital, Paramus, New Jersey, United States of America; and, Section of Anaesthesiology and Pain Medicine, Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, United States of America
Leith C.R. Meyer, Centre for Veterinary Wildlife Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa; and, Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa
Peter Buss, Veterinary Wildlife Services, Kruger National Park, South African National Parks, Skukuza, South Africa; and, Department of Production Animal Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa
María C. Fàbregas, Centre for Veterinary Wildlife Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa; and, Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa
Robin D. Gleed, Section of Anaesthesiology and Pain Medicine, Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, United States of America
Jordyn M. Boesch, Section of Anaesthesiology and Pain Medicine, Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, United States of America
Friederike Pohlin, Centre for Veterinary Wildlife Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa; and, Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa; and, Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Vienna, Austria


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Abstract

Etorphine–azaperone is the most commonly used drug combination for chemical immobilisation of free-ranging white rhinoceroses, but causes several profound physiological disturbances, including muscle tremors. The addition of benzodiazepine sedatives, such as midazolam, has been proposed to reduce the muscular rigidity and tremors in immobilised rhinoceroses. Twenty-three free-ranging, sub-adult white rhinoceros bulls were darted and captured using a combination of etorphine plus either azaperone or midazolam. Skeletal muscle tremors were visually evaluated and scored by an experienced veterinarian, and tremor scores and distance run were compared between groups using the Wilcoxon rank sum test. No statistical differences were observed in tremor scores (p = 0.435) or distance run (p = 0.711) between the two groups, and no correlation between these variables was detected (r = –0.628; p = 0.807). Etorphine–midazolam was as effective as etorphine–azaperone at immobilising rhinoceroses, with animals running similar distances. Although the addition of midazolam to the etorphine did not reduce tremor scores compared to azaperone, it might have other beneficial immobilising effects in rhinoceroses, and further investigation is necessary to elucidate possible methods of reducing muscle tremoring during chemical immobilisation of rhinoceroses.

Keywords

white rhinoceros; muscle tremors; etorphine; midazolam; azaperone; immobilisation; muscle relaxation; butorphanol

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