THE PULMONARY AND METABOLIC EFFECTS OF SUSPENSION BY THE FEET COMPARED WITH LATERAL RECUMBENCY IN IMMOBILIZED BLACK RHINOCEROSES (DICEROS BICORNIS) CAPTURED BY AERIAL DARTING.

Aerial translocation of captured black rhinoceroses (Diceros bicornis) has been accomplished by suspending them by their feet. We expected this posture would compromise respiratory gas exchange more than would lateral recumbency. Because white rhinoceroses (Ceratotherium simum) immobilized with etorphine alone are hypermetabolic, with a high rate of carbon dioxide production (VCO2), we expected immobilized black rhinoceroses would also have a high VCO2. Twelve (nine male, three female; median age 8 yr old [range: 4-25]; median weight 1,137 kg [range: 804-1,234] body weight) wild black rhinoceroses were immobilized by aerial darting with etorphine and azaperone. The animals were in lateral recumbency or suspended by their feet from a crane for approximately 10 min before data were collected. Each rhinoceros received both treatments sequentially, in random order. Six were in lateral recumbency first and six were suspended first. All animals were substantially hypoxemic and hypercapnic in both postures. When suspended by the feet, mean arterial oxygen pressure (PaO2) was 42 mm Hg, 4 mm Hg greater than in lateral recumbency (P=0.030), and arterial carbon dioxide pressure (PaCO2) was 52 mm Hg, 3 mm Hg less than in lateral recumbency (P=0.016). Tidal volume and minute ventilation were similar between postures. The mean VCO2 was 2 mL/kg/min in both postures and was similar to, or marginally greater than, VCO2 predicted allometrically. Suspension by the feet for 10 min did not impair pulmonary function more than did lateral recumbency and apparently augmented gas exchange to a small degree relative to lateral recumbency. The biological importance in these animals of numerically small increments in PaO2 and decrements in PaCO2 with suspension by the feet is unknown. Black rhinoceroses immobilized with etorphine and azaperone were not as hypermetabolic as were white rhinoceroses immobilized with etorphine.

Do potent immobilising-opioids induce different physiological effects in impala and blesbok?

Potent opioids are known to cause negative alterations to the physiology of immobilised antelope. How these effects differ between species has not been studied. This study aimed to compare time to recumbence and effects of opioid-based immobilisation on the physiology of impala (Aepyceros melampus) and blesbok (Damaliscus pygargus phillipsi). Eight animals of each species were immobilised, with 0.09 mg/kg etorphine and 0.09 mg/kg thiafentanil respectively, in a randomised two-way cross-over study. Variables measured and analysed by means of a linear mixed model included time to recumbence, heart rate, respiratory rate, arterial blood pressure, blood gases, lactate and glucose. In blesbok, mean time to recumbence was not significantly different with either drug (2.5 minutes and 2.2 min, respectively), but in impala thiafentanil achieved a shorter time to recumbence (2.0 min) than etorphine (3.9 min). Mean heart rates of immobilised impala were within reported physiological limits, but lower in immobilised blesbok when both opioids were used (35 beats/min to 44 beats/min vs. 104 ± 1.4 beats/min resting heart rate). Impala developed severe respiratory compromise and hypoxaemia from both opioids (overall mean PaO2 values ranged from 38 mmHg to 59 mmHg over 30 min). In contrast, blesbok developed only moderate compromise. Therefore, significantly different species-specific physiological responses to potent opioid drugs exist in blesbok and impala. Given that these different responses are clinically relevant, extrapolation of immobilising drug effects from one species of African ungulate to another is not recommended.

EVALUATION OF THE QUALITY OF IMMOBILIZATION AND CARDIORESPIRATORY EFFECTS OF ETORPHINE-MEDETOMIDINE-AZAPERONE COMBINATION IN PLAINS ZEBRAS (EQUUS QUAGGA): A PILOT STUDY.

Five free-ranging male (subadults, n = 3; adults, n = 2) plains zebras (Equus quagga) were immobilized using a combination of etorphine (0.017 mg/kg), medetomidine (0.017 mg/kg), and azaperone (0.24 mg/kg) by means of a blank cartridge-fired projector. Time to recumbency was recorded and a descriptive score used to assess the quality of immobilization, manipulation, maintenance, and recovery. Physiological parameters were recorded at 5-min intervals for 20 min. At the end of the procedure, naltrexone (0.23 mg/kg) was administered intramuscularly and time to standing documented. The combination evaluated in this study allowed for successful immobilization and safe recovery of all animals, including during the subsequent 15 days. Despite the good outcome in this pilot study, as a result of the periodic apneic events and hypercapnia documented in the zebras, the authors suggest that physiological parameters be thoroughly monitored when using this protocol. Further studies are needed to improve upon chemical immobilization protocols in free-ranging plains zebras.

Analgesic and Respiratory Depressant Effects of R-dihydroetorphine: A Pharmacokinetic-Pharmacodynamic Analysis in Healthy Male Volunteers.

BACKGROUND: There is an ongoing need for potent opioids with less adverse effects than commonly used opioids. R-dihydroetorphine is a full opioid receptor agonist with relatively high affinity at the µ-, δ- and κ-opioid receptors and low affinity at the nociception/orphanin FQ receptor. The authors quantified its antinociceptive and respiratory effects in healthy volunteers. The authors hypothesized that given its receptor profile, R-dihydroetorphine will exhibit an apparent plateau in respiratory depression, but not in antinociception. METHODS: The authors performed a population pharmacokinetic-pharmacodynamic study (Eudract registration No. 2009-010880-17). Four intravenous R-dihydroetorphine doses were studied: 12.5, 75, 125, and 150 ng/kg (infused more than 10 min) in 4 of 4, 6 of 6, 6 of 6, and 4 of 4 male subjects in pain and respiratory studies, respectively. The authors measured isohypercapnic ventilation, pain threshold, and tolerance responses to electrical noxious stimulation and arterial blood samples for pharmacokinetic analysis. RESULTS: R-dihydroetorphine displayed a dose-dependent increase in peak plasma concentrations at the end of the infusion. Concentration-effect relationships differed significantly between endpoints. R-dihydroetorphine produced respiratory depression best described by a sigmoid EMAX-model. A 50% reduction in ventilation in between baseline and minimum ventilation was observed at an R-dihydroetorphine concentration of 17 ± 4 pg/ml (median ± standard error of the estimate). The maximum reduction in ventilation observed was at 33% of baseline. In contrast, over the dose range studied, R-dihydroetorphine produced dose-dependent analgesia best described by a linear model. A 50% increase in stimulus intensity was observed at 34 ± 11 pg/ml. CONCLUSIONS: Over the dose range studied, R-dihydroetorphine exhibited a plateau in respiratory depression, but not in analgesia. Whether these experimental advantages extrapolate to the clinical setting and whether analgesia has no plateau at higher concentrations than investigated requires further studies.

Compared to etorphine-azaperone, the ketamine-butorphanol-medetomidine combination is also effective at immobilizing zebra (Equus zebra).

OBJECTIVE: To compare immobilization efficacy of a nonpotent opioid drug combination, ketamine-butorphanol-medetomidine (KBM) to the preferred etorphine-azaperone (EA) combination in zebras. STUDY DESIGN: Randomized crossover trial. ANIMALS: A group of ten adult zebra (six females and four male). METHODS: KBM and EA were administered once to the zebras in random order by dart, 3 weeks apart. Once a zebra was recumbent and instrumented, physiological parameters were measured and recorded at 5-minute intervals until 20 minutes. Antagonist drugs were administered at 25 minutes. KBM was antagonised using atipamezole (7.5 mg mg-1 medetomidine dose) and naltrexone (2 mg mg-1 butorphanol dose). EA was antagonized using naltrexone (20 mg mg-1 etorphine dose). Induction and recovery (following antagonist administration) times were recorded. Physiological parameters, including invasive blood pressure and blood gas analysis, were compared between combinations using a general linear mixed model. Data are reported as mean ± standard deviation or median (interquartile range). RESULTS: The doses of KBM and EA administered were 3.30 ± 0.18, 0.40 ± 0.02 and 0.16 ± 0.01 mg kg-1; and 0.02 ± 0.001 and 0.20 ± 0.01 mg kg-1, respectively. KBM and EA induction times were 420 (282-564) and 240 (204-294) seconds, respectively (p = 0.03). Zebras remained recumbent throughout the study procedures. Systolic blood pressure (226 ± 42 and 167 ± 42 mmHg) and oxygen partial pressure (64 ± 12 and 47 ± 13 mmHg) were higher for KBM compared to EA (p < 0.01). Recovery time, after administering antagonists, was 92 (34-1337) and 26 (22-32) seconds for KBM and EA, respectively (p = 0.03). CONCLUSIONS AND CLINICAL RELEVANCE: Compared to EA, KBM also immobilized zebras effectively. Systemic hypertension and moderate hypoxaemia are clinical concerns of KBM and severe hypoxaemia is a concern of EA. This occurrence of hypoxaemia highlights the importance of oxygen administration during immobilization.

Chemical capture of wild swamp buffalo (Bubalus bubalis) in tropical northern Australia using thiafentanil, etorphine and azaperone combinations.

BACKGROUND: Studying wild animals in situ is fundamental to collecting baseline information, but generally they need to be immobilised for examination, sampling, marking and/or equipping with tracking apparatus. Capturing wild animals is inherently risky and there is a need for immobilisation methods that are safe for both the animals and researchers. METHODS: A total of 16 free-ranging swamp buffalo (Bubalus bubalis) were chemically captured by dart for the application of satellite tracking collars in tropical northern Australia; 7 animals were anesthetised with a thiafentanil-etorphine-azaperone (TEA) combination and 9 animals with a thiafentanil-azaperone (TA) combination. Anaesthesia was reversed with intravenous naltrexone. Mean dosages of etorphine and thiafentanil for animals in the TEA group were 0.01 mg/kg of each drug and mean dosage of thiafentanil for animals in the TA group was 0.02 mg/kg. Total dose per animal of azaperone and naltrexone was 80 mg and 150 mg, respectively. Anaesthetic monitoring was by physical observation of physiological variables, pulse oximetry and capnography. Blood laboratory parameters including creatine kinase (CK), aspartate transaminase (AST), serum bicarbonate and anion gap were measured. RESULTS: All subject animals recovered well from anaesthesia despite the occurrence of subclinical acidosis in some patients. There was no significant difference between the treatment groups. Conversely, chase time had an adverse effect on body temperature, irrespective of the anaesthetic combination used. CONCLUSIONS: Thiafentanil and azaperone, with or without etorphine, delivered rapid safe, effective, reversible field anaesthesia in healthy swamp buffalo.

EFFECTS OF A SUPPLEMENTAL ETORPHINE DOSE ON PULMONARY ARTERY PRESSURE AND CARDIAC OUTPUT IN IMMOBILIZED, BOMA-HABITUATED WHITE RHINOCEROS ( CERATOTHERIUM SIMUM): A PRELIMINARY STUDY.

The effects of etorphine on the pulmonary vascular system of white rhinoceros ( Ceratotherium simum) have not been described and could play a role in the severe hypoxemia that develops after immobilization with etorphine-based drug combinations. Characterization of these effects requires measurement of pulmonary vascular pressures and cardiac output (CO). To refine a technique for pulmonary arterial catheterization, five boma-habituated white rhinoceros (three females and two males weighing 1,012-1,572 kg) were immobilized by remote injection with etorphine plus azaperone followed by butorphanol. This afforded the opportunity to perform a pilot study and acquire preliminary measurements of pulmonary arterial pressure (PAP) and CO before and after supplemental etorphine given intravenously. Ultrasonographic guidance was used to insert a sheath introducer into a linguofacial branch of a jugular vein. A 160-cm-long pulmonary artery catheter with a balloon and thermistor was then passed through the introducer and positioned with its tip in the pulmonary artery. It was not long enough to permit wedging for measurement of pulmonary artery occlusion pressure. Mean PAP was 35 mm Hg (minimum, maximum 32, 47 mm Hg) and increased ( P = 0.031) by 83% (28, 106%) after supplemental etorphine. Thermodilution CO was 120 L/min (92, 145 L/min) and increased 27% (3, 43%) ( P = 0.031). Heart rate was 100 (88, 112) beats/min and increased 20% (4, 45%) ( P = 0.031), whereas arterial partial pressure of oxygen was 35 mm Hg (30, 94 mm Hg) and decreased 47% (20, 72%) ( P = 0.031). The cardiovascular observations could result from etorphine-induced generalized sympathetic outflow, as has been reported in horses. Further studies of etorphine in isolation are needed to test this suggestion and to discern how the changes in pulmonary vascular pressures and blood flow might relate to hypoxemia in etorphine-immobilized white rhinoceros.

IMMOBILIZING MUSKOX ( OVIBOS MOSCHATUS) UNDER HIGH ARCTIC CONDITIONS.

Immobilizing and handling large, free-ranging animals without proper facilities in harsh environmental conditions poses significant challenges. During two field expeditions, a total of 29 female muskoxen ( Ovibos moschatus) were immobilized in Northeast Greenland (74°N, 20°E). Fixed doses of immobilizing drugs were used regardless of animal size: 2 mg etorphine, 30 mg xylazine, 0.3 mg medetomidine, and 40 mg ketamine. Physiologic and behavioral monitoring was performed during the second expedition on 15 female muskoxen. The observed heart rates were 35-58 beats/min and respiratory rates were 25-30 breaths/min. Mean arterial pressures measured using oscillometry ranged between 117-142 mmHg. Pulse oximeter readings ranged from 91-98% with oxygen supplementation, nasal end-tidal carbon dioxide values were 24-42 mmHg, and rectal temperature ranged from 38.9-39.6°C. Induction time was 6-8 min, recovery time 2-6 min after reversal, and duration of anesthesia was 50-100 min. This anesthetic regime thus provided reliable immobilization with minimal pathophysiologic alterations.

REPEATED ANESTHESIA IN A BLACK RHINOCEROS ( DICEROS BICORNIS) TO MANAGE UPPER RESPIRATORY OBSTRUCTION.

This report describes weekly repeated anesthesia in a 7-yr-old, 1,030 kg, female Eastern black rhinoceros ( Diceros bicornis michaeli), that was immobilized six times using a combination of 2 mg etorphine (0.002 mg/kg), 5 mg medetomidine (0.005 mg/kg), 25 mg midazolam (0.024 mg/kg), and 300 mg ketamine (0.29 mg/kg) delivered intramuscularly (IM) via remote dart to facilitate long-term medical care of a bilateral, obstructive Actinomyces sp. rhinitis. The drug combination described in this study resulted in reliable, rapid recumbency of the animal within 2-8 min after initial administration via dart and produced deep anesthesia for 34-78 min without supplemental anesthetic administration. Antagonist drugs (100 mg naltrexone [0.1 mg/kg] and 25 mg atipamezole [0.024 mg/kg] IM) produced reliable and uneventful recoveries in all the procedures. During each anesthetic procedure, the animal was intubated and provided intermittent positive pressure ventilation with a megavertebrate demand ventilator. Tachycardia and hypoxia noted after induction resolved after positive pressure ventilation with oxygen. This report provides useful information on a novel anesthetic protocol used repeatedly for intensive medical management in a black rhinoceros.

A RETROSPECTIVE COMPARISON OF CHEMICAL IMMOBILIZATION WITH THIAFENTANIL, THIAFENTANIL-AZAPERONE, OR ETORPHINE-ACEPROMAZINE IN CAPTIVE PERSIAN FALLOW DEER (DAMA DAMA MESOPOTAMICA).

Records of 56 Persian fallow deer (Dama dama mesopotamica) immobilized for translocation were reviewed. Twenty-three were administered 0.05 ± 0.01 (mean ± SD) mg/kg thiafentanil (THIA), 20 were administered 0.045 ± 0.008 mg/kg thiafentanil combined with 0.19 ± 0.03 mg/kg azaperone (THIA-AZP), and 13 were administered 0.032 ± 0.04 mg/kg etorphine-acepromazine (ETOR-ACP) by intramuscular remote injection. Parameters recorded and compared between groups included induction and recovery times, heart rate, respiratory rate, rectal temperature, oxygen saturation, blood pressure, reflexes, quality of immobilization, and blood concentrations of lactate and glucose. Naltrexone (THIA groups) or diprenorphine (ETOR-ACP) were administered for reversal. Mean induction time was significantly shorter in the THIA group versus the ETOR-ACP group (2.0 ± 1.3 and 4.8 ± 2.8 min, respectively), but not significantly shorter than the THIA-AZP group (2.8 ± 3.1 min). Respiratory rate was significantly higher in the THIA group in comparison to the two other groups. None of the protocols provided excellent immobilization quality, which was significantly poorer in the THIA group. Following antagonist administration, all deer from the THIA and ETOR-ACP groups recovered quickly, while there were five perianesthetic morbidity and mortality cases in the THIA-AZP group. Mean recovery time was significantly shorter in the THIA group versus the THIA-AZP and ETOR-ACP groups (0.5 ± 0.3, 1.1 ± 0.8, and 2.3 ± 1.1 min, respectively). In conclusion, the use of THIA provided faster induction and recovery, with less respiratory depression, but poorer immobilization. The THIA-AZP combination should be used with caution in Persian fallow deer until further investigation.

Comparison of thiafentanil-medetomidine to etorphine-medetomidine immobilisation of impalas (Aepyceros melampus).

Impalas (Aepyceros melampus) are increasingly valuable in the South African wildlife industry, and there is a greater need to chemically immobilise them, ideally with minimal risk. This study aimed to compare the times to recumbency and physiological effects of thiafentanilmedetomidine versus etorphine-medetomidine immobilisation. A combination of thiafentanil (2 mg) + medetomidine (2.2 mg) and etorphine (2 mg) + medetomidine (2.2 mg) was administered (to nine impalas; crossover design) via a dart. After darting, a stopwatch was started to record times to recumbency (time from darting until recumbent without attempts to stand). If apnoea was present, the impalas received one or more boluses of butorphanol (1:1 potent opioid dose). Data collection included arterial blood gas analysis and the number of butorphanol boluses. Two-sample t-tests were used to compare differences between combinations. The time to recumbency for thiafentanil-medetomidine was 12.2 (± 6.8) min and no different from 14.5 (± 5.2) min for etorphine-medetomidine (p = 0.426). The thiafentanilmedetomidine combination required more butorphanol boluses (median: 2; interquartile range: 2-3) compared to etorphine-medetomidine (median: 0; interquartile range: 0-1) (p = 0.001). Despite butorphanol treatment and resolution of apnoea, all impalas suffered hypoxaemia (PaO2 ± 44.0 mmHg). Thiafentanil-medetomidine did not immobilise impalas more rapidly than etorphine-medetomidine, and resulted in more apnoea that required rescue butorphanol boluses. Marked hypoxaemia resulted from both combinations, mainly because of right-to-left intrapulmonary shunting and not because of hypoventilation. Butorphanol and oxygen supplementation should be considered as essential rescue interventions for all impalas immobilised with these potent opioid combinations.

Blood acid-base status in impala (Aepyceros melampus) immobilised and maintained under total intravenous anaesthesia using two different drug protocols.

BACKGROUND: In mammals, homeostasis and survival are dependent on effective trans-membrane movement of ions and enzyme function, which are labile to extreme acid-base changes, but operate efficiently within a narrow regulated pH range. Research in patients demonstrating a pH shifts outside the narrow regulated range decreased the cardiac output and systemic vascular resistance and altered the oxygen binding to haemoglobin. These cardiopulmonary observations may be applicable to the risks associated with anaesthesia and performance of wildlife ungulates on game farms. The aim of this study was to compare blood pH changes over time in impala immobilised and anaesthetised with two different drug protocols (P-TMP - immobilisation: thiafentanil-medetomidine; maintenance: propofol-ketamine-medetomidine; P-EME - immobilisation: etorphine-medetomidine; maintenance: etorphine-ketamine-medetomidine). Additionally, we discuss the resultant blood pH using both the Henderson-Hasselbalch and the Stewart approaches. Two data collection time points were defined, Time1 before maintenance of general anaesthesia and Time 2 at end of maintenance of general anaesthesia. We hypothesise that blood pH would not be different between drug protocols and would not change over time. RESULTS: Significant differences were detected over time but not between the two drug protocols. Overall, the blood pH decreased over time from 7.37 ± 0.04 to 7.31 ± 0.05 (p = 0.001). Overall, over time arterial partial pressure of carbon dioxide changed from 51.3 ± 7.5 mmHg to 72.6 ± 12.4 mmHg (p < 0.001); strong ion difference from 44.6 ± 2.4 mEq/L to 46.9 ± 3.1 mEq/L (p < 0.001); anion gap from 15.0 ± 3.1 mEq/L to 10.9 ± 2.2 mEq/L (p < 0.001); and total weak acids from 16.1 ± 1.2 mmol/L to 14.0 ± 1.1 mmol/L (p < 0.001). The bicarbonate changed from 29.6 ± 2.7 mEq/L to 36.0 ± 4.1 mEq/L (p < 0.001); and lactate changed from 2.9 ± 1.5 mEq/L to 0.3 ± 0.03 mEq/L (p < 0.001) over time. CONCLUSIONS: The profound increase in the partial pressure of carbon dioxide that worsened during the total intravenous anaesthesia in both protocols initiated a substantial metabolic compensatory response to prevent severe acidaemia. This compensation resulted in a clinically acceptable mild acidaemic state, which worsened over time but not between the protocols, in healthy impala. However, these important compensatory mechanisms require normal physiological function and therefore when immobilising ill or anorexic wild ungulates their acid-base status should be carefully assessed.

CONTINUOUS INTRAVENOUS INFUSION ANESTHESIA WITH MEDETOMIDINE, KETAMINE, AND MIDAZOLAM AFTER INDUCTION WITH A COMBINATION OF ETORPHINE, MEDETOMIDINE, AND MIDAZOLAM OR WITH MEDETOMIDINE, KETAMINE, AND BUTORPHANOL IN IMPALA (AEPYCEROS MELAMPUS).

In order to develop a long-term anesthesia for flighty antelope species in field situations, two different protocols for induction and maintenance with an intravenous infusion were evaluated in wild-caught impala ( Aepyceros melampus ). Ten adult female impala were induced with two induction protocols: one consisted of 0.2 mg/kg medetomidine, 4 mg/kg ketamine, and 0.15 mg/kg butorphanol (MKB) and one consisted of 0.375 mg/kg etorphine, 0.2 mg/kg medetomidine, and 0.2 mg/kg midazolam (EMM). In both treatments, anesthesia was maintained with a continuous intravenous infusion (CII) at an initial dose rate of 1.2 µg/kg per hr medetomidine, 2.4 mg/kg per hr ketaminen and 36 µg/kg per hr midazolam. Partial reversal was achieved with naltrexone (2 : 1 mg butorphanol; 20 : 1 mg etorphine) and atipamezole (5 : 1 mg medetomidine). Evaluation of anesthesia included respiratory rate, heart rate, rectal temperature, arterial blood pressure, oxygen saturation, end tidal carbon dioxide tension, and tidal volume at 5-min intervals, palpebral reflex and response to painful stimuli at 15-min intervals, and arterial blood gases at 30-min intervals. Plasma cortisol concentration was determined after induction and before reversal. Duration and quality of induction and recovery were evaluated. EMM caused a faster induction of 9.5 ± 2.9 min compared to 11.0 ± 6.4 min in MKB. Recovery was also quicker in EMM (EMM: 6.3 ± 5.4 min; MKB: 9.8 ± 6.0 min). However, EMM also produced more cardiopulmonary side effects, including hypoxemia and hypercapnia, and calculated oxygenation indices (PaCO2-PETCO2) were worse than in MKB. One animal died after induction with EMM. The CII provided surgical anesthesia in 7 of 10 animals in MKB and in 9 of 9 animals in EMM for 120 min. In conclusion, the MKB induction protocol had advantages for prolonged anesthesia in impala with significantly less cardiopulmonary depression compared to EMM. The comparably decreased anesthetic depth could easily be adjusted by an increase of the CII.

Severe Hypoxemia in Muskoxen ( Ovibos moschatus ) Immobilized with Etorphine and Xylazine Corrected with Supplemental Nasal Oxygen.

Twenty-three muskoxen ( Ovibos moschatus ) housed in a captive facility for rewilding in Sweden were chemically immobilized for annual health evaluations and hoof trimming. The muskoxen were darted in May to September (2012-15) in their holding pen with etorphine (0.015 mg/kg) and xylazine (0.1 mg/kg) intramuscularly. Twenty-two of the 23 animals were immobilized with a single dart injection. The mean (SD) induction time was 4 (2) min. Arterial blood gases were collected from 18 animals. All animals were severely hypoxemic with varying degrees of respiratory acidosis. The hypoxemia resolved in 17 of 18 animals with intranasal oxygen supplementation at 1 L/min per 100 kg. Relative arterial oxygen saturation (SpO2) measured by pulse oximetry was significantly higher than the arterial oxygen saturation calculated from the partial pressure of arterial oxygen (SaO2) obtained by a blood gas analyzer. Based on these findings, muskox can be immobilized successfully with etorphine (0.015 mg/kg) and xylazine (0.1 mg/kg) but should receive supplemental oxygen.

EVALUATION OF ETORPHINE AND MIDAZOLAM ANESTHESIA, AND THE EFFECT OF INTRAVENOUS BUTORPHANOL ON CARDIOPULMONARY PARAMETERS IN GAME-RANCHED WHITE RHINOCEROSES (CERATOTHERIUM SIMUM).

Nineteen white rhinoceroses ( Ceratotherium simum ) were anesthetized with 4 mg of etorphine hydrochloride; 35-40 mg of midazolam; and 7,500 international units of hyaluronidase for dehorning purposes at a game ranch in South Africa, to investigate this anesthetic combination. Median time to recumbency was 548 sec (range 361-787 sec). Good muscle relaxation and no muscle rigidity or tremors were observed in 18 animals, and only 1 individual showed slight tremors. In addition, all animals received butorphanol i.v. 5 min after recumbency at the ratio of 10 mg of butorphanol per 1 mg of etorphine. Blood gas and selected physiologic parameters were measured in the recumbent animal, immediately before and 10 min after the administration of butorphanol. Statistically significant improvements were observed in blood gas physiologic and cardiopulmonary parameters 10 min after the administration of butorphanol, with a reduction in arterial partial pressure of carbon dioxide, systolic blood pressure, and heart rate and an increase in pH, arterial partial pressure of oxygen, oxygen saturation, and respiratory rate (all P < 0.005). After i.v. naltrexone reversal, recovery was uneventful, and median time to walking or running was 110 sec (range 71-247 sec). The results indicate etorphine and midazolam combination is an effective alternative anesthetic protocol and produces good muscle relaxation. Furthermore, i.v. butorphanol was associated with improved blood gas values and cardiopulmonary function for at least 10 min postinjection.

CARDIOVASCULAR EFFECTS OF ETORPHINE, AZAPERONE, AND BUTORPHANOL COMBINATIONS IN CHEMICALLY IMMOBILIZED CAPTIVE WHITE RHINOCEROS (CERATOTHERIUM SIMUM).

Chemical capture is an essential tool in the management and conservation of white rhinoceros ( Ceratotherium simum ); however, cardiovascular responses in immobilized megaherbivores are poorly understood. Blood pressure and heart rate responses in rhinoceros immobilized with etorphine or etorphine plus azaperone, and the effects of subsequent i.v. butorphanol administration were investigated. Six white rhinoceros were used in a randomized crossover study design with four interventions: 1) etorphine i.m.; 2) etorphine plus azaperone i.m.; 3) etorphine i.m. and butorphanol i.v.; and 4) etorphine plus azaperone i.m., and butorphanol i.v. Etorphine resulted in hypertension and tachycardia in immobilized rhinoceros on initial measurements. Over the 25-min study period, blood pressures and heart rate declined. Heart rates were slower, although the rhinoceros were still tachycardic, and blood pressures lower during the whole study period in animals immobilized with etorphine and azaperone compared with those that received only etorphine. Butorphanol administration resulted in lower arterial blood pressures and heart rates in etorphine-immobilized rhinoceros. In rhinoceros immobilized with etorphine and azaperone, heart rate slowed following administration of butorphanol i.v., although blood pressures remained unchanged. Azaperone reduced hypertension associated with etorphine immobilization, but animals remained tachycardic. Administration of butorphanol to etorphine/azaperone-immoblized rhinoceros lowered heart rate to values approaching normal resting levels without altering blood pressure.

Arterial pH and Blood Lactate Levels of Anesthetized Mongolian Khulan ( Equus hemionus hemionus) in the Mongolian Gobi Correlate with Induction Time.

Research and conservation of wide-ranging wild equids in most cases necessitate capture and handling of individuals. For free-roaming Mongolian khulan ( Equus hemionus hemionus), also known as the khulan, capture involves a strenuous, high-speed chase, and physiologic responses have yet to be elucidated. We analyzed sequential arterial blood gas (ABG) samples as a proxy for respiratory and metabolic status of khulan during capture-related anesthesia. We recorded precise chase and induction times and monitored vital parameters and ABG from free-ranging khulan during anesthesia performed for GPS collaring. At the initiation of anesthesia, animals had ABG values similar to those recorded for thoroughbred horses ( Equus caballus ) after maximal exercise. Longer induction times resulted in higher arterial pH (P<0.001) and lower blood lactate (P<0.002). This trend of improvement continued over the course of anesthesia. The most important factor explaining pH and lactate was the time that elapsed between cessation of the chase and obtaining the first ABG sample, which, under field conditions, is tightly linked to induction time. All animals recovered uneventfully. Our data show that khulan recover and shift their metabolic status back toward expected normal values during opioid-based field anesthesia.

Pulmonary gas exchange and acid-base status during immobilisation of black rhinoceroses (Diceros bicornis) in Zimbabwe.

When immobilising wildlife, adverse side effects can include hypoxaemia, acidosis and hypertension. Pulmonary gas exchange and acid-base status were evaluated during immobilisation of 25 free-ranging and one boma-held black rhinoceros (Diceros bicornis) in Zimbabwe. The effect of different body positions on arterial oxygenation was evaluated. A combination of the following drugs was used: an opioid (etorphine or thiafentanil), azaperone and an a2 -adrenoceptor agonist (detomidine or xylazine). Respiratory and heart rates, rectal temperature and pulse oximetry-derived haemoglobin oxygen saturation were recorded. Serial arterial blood samples were analysed immediately in the field. Marked hypoxaemia and hypercapnia were recorded in immobilised free-ranging black rhinoceroses. Arterial oxygenation was higher during sternal compared to lateral recumbency. Most rhinoceroses developed acidaemia of respiratory and metabolic origin. Initially high lactate concentrations in free-ranging rhinoceroses decreased during immobilisation. Pulse oximetry was unreliable in the detection of hypoxaemia. Positioning in sternal recumbency and routine use of oxygen supplementation are recommended in the management of immobilised rhinoceroses as measures to improve arterial oxygenation.

ETORPHINE-KETAMINE-MEDETOMIDINE TOTAL INTRAVENOUS ANESTHESIA IN WILD IMPALA (AEPYCEROS MELAMPUS) OF 120-MINUTE DURATION.

There is a growing necessity to perform long-term anesthesia in wildlife, especially antelope. The costs and logistics of transporting wildlife to veterinary practices make surgical intervention a high-stakes operation. Thus there is a need for a field-ready total intravenous anesthesia (TIVA) infusion to maintain anesthesia in antelope. This study explored the feasibility of an etorphine-ketamine-medetomidine TIVA for field anesthesia. Ten wild-caught, adult impala ( Aepyceros melampus ) were enrolled in the study. Impala were immobilized with a standardized combination of etorphine (2 mg) and medetomidine (2.2 mg), which equated to a median (interquartile range [IQR]) etorphine and medetomidine dose of 50.1 (46.2-50.3) and 55.1 (50.8-55.4) µg/kg, respectively. Recumbency was attained in a median (IQR) time of 13.9 (12.0-16.5) min. Respiratory gas tensions, spirometry, and arterial blood gas were analyzed over a 120-min infusion. Once instrumented, the TIVA was infused as follows: etorphine at a variable rate initiated at 40 µg/kg per hour (adjusted according to intermittent deep-pain testing); ketamine and medetomidine at a fixed rate of 1.5 mg/kg per hour and 5 µg/kg per hour, respectively. The etorphine had an erratic titration to clinical effect in four impala. Arterial blood pressure and respiratory and heart rates were all within normal physiological ranges. However, arterial blood gas analysis revealed severe hypoxemia, hypercapnia, and acidosis. Oxygenation and ventilation indices were calculated and highlighted possible co-etiologies to the suspected etorphine-induced respiratory depression as the cause of the blood gas derangements. Impala recovered in the boma post atipamezole (13 mg) and naltrexone (42 mg) antagonism of medetomidine and etorphine, respectively. The etorphine-ketamine-medetomidine TIVA protocol for impala may be sufficient for field procedures of up to 120-min duration. However, hypoxemia and hypercapnia are of paramount concern and thus oxygen supplementation should be considered mandatory. Other TIVA combinations may be superior and warrant further investigation.

COMPARISON OF ETORPHINE-ACEPROMAZINE AND MEDETOMIDINE-KETAMINE ANESTHESIA IN CAPTIVE IMPALA (AEPYCEROS MELAMPUS).

Impala (Aepyceros melampus) are a notoriously difficult species to manage in captivity, and anesthesia is associated with a high risk of complications including mortality. The aim of this study was to compare an opioid-based protocol with an α-2 agonist-based protocol. Nine female impala were studied in a random cross-over design. Subjects received either an etorphine-acepromazine (EA) protocol: 15 µg/kg etorphine and 0.15 mg/kg acepromazine, or a medetomidine-ketamine (MK) protocol: 109 µg/kg medetomidine and 4.4 mg/kg ketamine on day 1. Anaesthesia was repeated 3 days later with the alternative protocol. Subjective assessments of the quality of induction, muscle relaxation, and recovery were made by a blinded observer. Objective monitoring included blood pressure, end-tidal CO2, regional tissue oxygenation, and blood gas analysis. EA provided a significantly quicker (mean EA, 7.17 mins; MK, 17.6 mins) and more-reliable (score range EA, 3-5; MK, 1-5) induction. Respiratory rates were lower for EA with higher end-tidal CO2, but no apnoea was observed. As expected, blood pressures with EA were lower, with higher heart rates; however, arterial oxygenation and tissue oxygenation were equal or higher than with the MK protocol. In conclusion, at these doses, EA provided superior induction and equivalent muscle relaxation and recovery with apparent improved oxygen tissue delivery when compared to MK.