Midazolam Alters Acid-Base Status Less than Azaperone during the Capture and Transport of Southern White Rhinoceroses (Ceratotherium simum simum)

Abstract

Acidemia represents a major life-threatening factor during rhinoceros capture. The acid-base status during rhinoceros transport is unknown. The purpose of this study was to describe changes in acid-base status during rhinoceros capture and transport and compare these changes between rhinoceroses sedated with azaperone or midazolam. Twenty-three wild white rhinoceros bulls were road-transported 280 km for reasons unrelated to this study. Rhinoceroses were captured with etorphine-azaperone (Group A) or etorphine-midazolam (Group M). During transport, azaperone (Group A) or midazolam (Group M) was re-administered every 2 h and venous blood collected. Changes in blood pH and associated variables were compared over time and between groups using a general linear mixed model. Rhinoceroses of both groups experienced a respiratory and metabolic acidosis during capture (pH 7.109 ± 0.099 and 7.196 ± 0.111 for Group A and Group M, respectively) that was quickly compensated for by the start of transport (pH 7.441 ± 0.035 and 7.430 ± 0.057) and remained stable throughout the journey. Rhinoceroses from Group M showed a smaller decrease in pH and associated variables at capture than rhinoceroses from Group A (p = 0.012). The use of midazolam instead of azaperone could therefore improve the success of rhinoceros capture and thus, contribute to the outcome of important conservation translocations.

Arterial Blood Gases and Cardiorespiratory Parameters in Etorphine-Medetomidine-Midazolam Immobilized Free-Ranging and Game-Farmed Southern White Rhinoceroses (Ceratotherium simum simum) Undergoing Electro-Ejaculation

“…Hypoxemia, hypercarbia, and respiratory and metabolic (lactic acid) acidemia are consistent findings in white rhinoceroses immobilized with etorphine-based combinations ( 6 , 11 , 12 , 14 – 16 , 26 ), and caused by several factors including pulmonary hypertension, hypoventilation, and hypermetabolism associated with the μ-receptor-related and sympathetic effects of the etorphine ( 34 – 36 ).…”

“…Additionally, as the ejaculatory reflex and semen emission are α-adrenergically mediated ( 22 ), α 2 -agonists were found to increase semen emission in felids ( 23 ) and stallions ( 24 ), and were suggested for the use in rhinoceroses undergoing electro-ejaculation ( 25 ). Midazolam, a benzodiazepine receptor agonist and potent sedative and muscle relaxant, was more recently incorporated in white rhinoceros immobilization protocols ( 12 , 15 , 26 , 27 ). By reducing muscle spasms and rigidity ( 28 ), ventilation is improved and the risk of hyperthermia and capture myopathy reduced ( 29 ).…”

A Comparison of Hematological, Immunological, and Stress Responses to Capture and Transport in Wild White Rhinoceros Bulls (Ceratotherium simum simum) Supplemented With Azaperone or Midazolam

“…Dose-and time-dependent immunomodulating effects of this drug need to be explored, as well as a potential antiinflammatory effect. Midazolam improves lactic acidosis during rhinoceros immobilization (80) and may reverse behavioral deficits associated with chronic stress (81). These benefits may be clinically more important than potential immunological side effects and need to be explored.…”

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

“…Data for this initial study were opportunistically collected from 23 free-ranging, sub-adult white rhinoceros bulls captured within the Kruger National Park (S24°59.696ʹE031°35.217), South Africa, for management purposes. Details concerning the immobilisation and data collected from these rhinoceroses are reported in Pohlin et al (2020a). Briefly, rhinoceroses were darted from a helicopter with a combination of etorphine (3 mg -4 mg, intramuscular [IM]; 9.8 mg/mL; Captivon ® , Wildlife Pharmaceuticals) plus either azaperone (n = 11, IM; azaperone tartrate 50 mg/mL; Wildlife Pharmaceuticals) or midazolam (n = 12, IM; Dazonil ® , 50 mg/mL; Wildlife Pharmaceuticals), both at five times the etorphine dose in milligram.…”

“…The addition of benzodiazepine sedatives, such as midazolam, has been proposed to reduce muscular rigidity and tremors in immobilised rhinoceroses (De Lange et al 2017;Pohlin et al 2020a). The drug's effect on gamma-aminobutyric acid (GABA A ) receptors results in skeletal muscle relaxation, making it a viable candidate to reduce muscle tremors (Izwan et al 2018).…”