Acid-Base Balance and Ventilation During Sternal and Lateral Recumbency in Field Immobilized Black Rhinoceros (Diceros Bicornis) Receiving Oxygen Insufflation: A Preliminary Report

Abstract

Posture, ventilation, and acid-base balance using auricular venous blood values (pH, lactate, base excess [BE], HCO(3)(-), PO(2), SO(2), and PCO(2)), oxygen saturation of hemoglobin (SpO(2)), and end-tidal carbon dioxide (P(ET)CO(2)) were compared between sternal (STE) and lateral (LAT) recumbency in free-ranging black rhinoceros (Diceros bicornis bicornis) receiving oxygen insufflation. Data are reported as median, minimum, and maximum (median [minimum, maximum]). Thirty-six desert-adapted black rhinoceros (20 male, 16 female; age 8 [1.5, 33] yr) were immobilized in Namibia in March and April of 2008, from a helicopter, by remote intramuscular injection with etorphine HCl, azaperone, and hyaluronidase. Time from darting to recumbency was 6.0 (3, 15.5) min. Data were organized into two sampling periods: sample period 1 (P1, collected within 0-20 min postdarting; 13 [6.5, 19] min) and sample period 2 (P2, collected between 20-40 min postdarting; 32 [22.3, 39] min). All animals were acidemic (pH 7.24 [7.07, 7.32]) and hypoxemic (PO(2) 51 [38, 95.2]; SO(2) 78 [64, 96] mmHg) after capture. Lactate at P1 was 7.2 (3.2, 16.8) mmol/l and decreased (P=0.01) to 4.6 (1.2, 10.9) mmol/l at P2. At P2, lactate was less (P=0.06) in LAT 3.5 (1.2, 8.6) mmol/l than in STE posture 7.4 (3.1, 10.9) mmol/l. In P2, PO(2), SO(2), and SpO(2) were higher (P=0.02, 0.10, and 0.01, respectively) in STE than in LAT. End-tidal carbon dioxide in LAT was 38 (26, 47) mmHg and increased (P<0.001) rapidly to 48 (37, 55) mmHg when animals were moved into STE; no corresponding change in PCO(2) was observed. These preliminary findings suggest that STE posture in recumbent black rhinoceros reduces dead-space ventilation and improves oxygenation. Lateral posture was associated with lower blood lactate, quicker lactate recovery, or both. It is possible that the posture of recumbent rhinoceros after capture affects lactate accumulation and clearance, or both, and procedures should consider positioning in order to enhance perfusion.

Anaesthetic management of a 10-month-old white rhinoceros (<i>Ceratotherium simum</i>) calf for emergency exploratory celiotomy

“…Surgical procedures requiring deep sedation or surgical anaesthesia in rhinoceroses to manage conditions such as rectal prolapse (Adams et al 2005;Silberman & Fulton 1979;Stegmann et al 2001), colic (Valverde et al 2010), cancer (Wack et al 2010), toe infections (Harrison et al 2011), and corneal damage (Esson et al 2006) have been described. Adult, free-ranging rhinoceroses are commonly immobilised with etorphine on its own or in combination with azaperone (Adams et al 2005;Bush et al 2004;Esson et al 2006;Harrison et al 2011;Hattingh & Knox 1994;Morkel et al 2010;Portas 2004;Stegmann et al 2001;Vanegas & Schaible 2007;Wack et al 2010;Walzer et al 2010). The rhinoceros calf in this case report was hand-reared and did not require opioid immobilisation to facilitate handling before induction of anaesthesia.…”

“…Due to the skin thickness on the leg, the results may be underestimated. Opioids, especially the more potent etorphine and carfentinil promote moderate to severe hypertension (Hattingh & Knox 1994;Morkel et al 2010;Portas 2004). The partial-agonists of the opioids may be used to decrease the respiratory depression and hypertensive effects associated with the potent opioids (Portas 2004).…”

“…Rhinoceroses are sensitive to opioids and readily experience respiratory depression, hypoxaemia, hypertension, pulmonary shunting and ventilation/perfusion mismatching (Hattingh & Knox 1994;Morkel et al 2010;Portas 2004;Silberman & Fulton 1979). Their large body size contributes to the difficulty in anaesthetising these patients (Portas 2004).…”

Improvement of arterial oxygenation in free-ranging moose (Alces alces) immobilized with etorphine-acepromazine-xylazine

“…Markedly decreased arterial oxygen partial pressure (P aO2 ) levels indicating severe hypoxemia has been documented in several wildlife species during immobilization. This seems to be most evident in wildlife species immobilized with opioids, with reported P aO2 values as low as 10 mmHg in rhebok ( Pelea capreolus ) [ 8 ] and <40 mmHg in species such as North American elk ( Cervus canadensis ), white rhinoceros ( Ceratotherium simum ), white-tailed deer ( Odocoileus virginianus ), impala ( Aepyceros melampus ), black rhinoceros ( Diceros bicornis ) and wood bison ( Bison bison athabascae ) [ 13 ]–[ 19 ].…”

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

“…Hypoglycemia in rhinoceroses of this study was hypothesized to be due to exertion associated with initial capture (hypoglycemia defined as serum glucose ,65 mg/ dl based on comparisons to mean reference values of captive animals; ISIS, 2002). Although a quantitative measure of exertion in captured rhinoceroses was unavailable, the changes in glucose and lactate between the initial and second samples were consistent with exertion (Morkel et al, 2010). Of the 28 rhinoceroses tested, 21 had samples with glucose values ,65 mg/dl at S1, with a range of 14-151 mg/dl.…”