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 )

Development of a novel immobilisation protocol for black-faced impala (Aepyceros melampus ssp. petersi) in Etosha National Park

Black-faced impala (Aepyceros melampus ssp. petersi) are endemic to Namibia where conservation management involves immobilisation and translocation, and mortality with current protocols is common. Critically evaluated field immobilisation protocols are needed to maximise animal safety. This prospective study was done in two phases: the first compared etorphine- and thiafentanil-based combinations, the second evaluated the influence of oxygen in impala receiving the thiafentanil-based combination. Animals (10 per group) received 50 mg ketamine (K) and 10 mg butorphanol (B), with either 2.0 mg etorphine (E) or 2.0 mg thiafentanil (T). A third group of ten impala were anaesthetised using TKB with supplemental nasal oxygen (O) at a rate of 5 L/minute. Behavioural, metabolic and physiological variables were assessed within five minutes of recumbency and at 10, 15, and 20 minutes post-recumbency. Statistical analyses for non-parametric data were performed to compare the treatment groups as well as time points; p ≤ 0.05 considered significant. Following darting, 7/10 EKB animals were standing when approached, compared to 2/20 in the thiafentanil treatment groups. Time to first effect was significantly higher for EKB (155 ± 105.7 seconds) compared to TKBO (61.5 ± 21.4 seconds). Time to sternal after darting was significantly higher with EKB (411.6 ± 174 seconds) compared to TKB (160.5 ± 85.4 seconds) and TKBO (166 ± 77.3 seconds). This study builds on previous work investigating the effects of potent opioids on impala and is the first evaluating their use in a field setting. The thiafentanil combination had a faster onset and resulted in a smoother induction than the etorphine combination. Additionally, oxygenation improved in animals receiving oxygen supplementation.

Immobilization of Captive Kulans (Equus hemionus kulan) Without Using Ultrapotent Opioids

Etorphine is widely used in zoological medicine for the immobilization of large herbivores. All reported immobilization protocols for kulans use etorphine as the primary immobilizing agent. However, etorphine can trigger severe side effects and is highly toxic for humans, its availability is occasionally limited for use in wildlife medicine. Therefore, two different alpha-2 agonist-based protocols for the general anesthesia of kulans were investigated and compared with the standard etorphine immobilization. In total, 21 immobilizations were performed within the scope of routine husbandry management at the Serengeti-Park Hodenhagen. Kulans were darted using a ketamine–medetomidine–midazolam–butorphanol (KMMB) protocol (n = 8, treatment group (TG) 1), a tiletamine–zolazepam–medetomidine–butorphanol (TZMB) protocol (n = 7, treatment group (TG) 2), or an etorphine–acepromazine–detomidine–butorphanol (EADB) protocol (n = 6, control group). Vital parameters included heart rate, respiratory rate, arterial blood pressure (invasive), end tidal CO₂ (etCO₂), electromyography and core body temperature, which were all assessed every 10 min. For blood gas analysis, arterial samples were collected 15, 30, 45 and 60 min after induction. Subjective measures of quality and efficacy included quality of induction, immobilization, and recovery. Time to recumbency was longer for TG 1 (9.00 ± 1.67 min) and TG 2 (10.43 ± 1.79 min) compared to the induction times in the control group (5.33 ± 1.93 min). Treatment group protocols resulted in excellent muscle relaxation, normoxemia and normocapnia. Lower pulse rates combined with systolic arterial hypertension were detected in the alpha-2 agonist-based protocols. However, only in TZMB-immobilized kulans, sustained severe systolic arterial hypertension was observed, with significantly higher values than in the TG 1 and the normotensive control group. At 60 min following induction, medetomidine and detomidine were antagonized with atipamezole IM (5 mg/mg medetomidine or 2 mg/mg detomidine), etorphine and butorphanol with naltrexone IV (2 mg/mg butorphanol or 50 mg/mg etorphine), and midazolam and zolazepam with flumazenil IV (0.3 mg per animal). All three combinations provided smooth and rapid recoveries. To conclude, the investigated treatment protocols (KMMB and TZMB) provided a safe and efficient general anesthesia in kulans with significantly better muscle relaxation, higher respiration rates and improved arterial oxygenation compared with the immobilizations of the control group. However, the control group (EADB) showed faster recoveries. Therefore, EADB is recommended for ultra-short immobilizations (e.g., microchipping and collaring), especially with free-ranging kulans where individual recovery is uncertain, whereas the investigated treatment protocols are recommended for prolonged medical procedures on captive kulans.

CAPTIVE MANAGEMENT OF WILD IMPALA ( AEPYCEROS MELAMPUS) DURING INTENSIVE IMMOBILIZATION AND GENERAL ANESTHESIA STUDY TRIALS

Immobilization and anesthesia of impala ( Aepyceros melampus) has become a popular research theme. This demand is brought about by the increased need to immobilize and anesthetize impala and other medium-sized wild ungulates because of their increased value in game ranching and zoological collections. To improve our understanding of immobilization and general anesthesia in these species, it is paramount to be able to study them in a practical, safe research environment that does not cause harm or unnecessary stress to the animals. This study aimed to scrutinize our management and welfare practices and scientific methods of 15 wild-caught impala placed in captive confinement during a 16-wk intensive research project. The scientific methods of the project were scrutinized to identify procedures that attributed to morbidity and mortality. Indicators of impala welfare during captivity were monitored by documenting serial physical (body weight, coat condition), physiological (biochemistry and hematology), and psychologic (behavioral) aspects. Two impala suffered irreparable femoral fractures during darting and were humanly euthanized. One impala suffered cardiovascular collapse during immobilization and could not be resuscitated. The procedure of chemical capture had a morbidity and mortality rate of 14.8% and 4.4%, respectively. The impala maintained acceptable physical and physiologic parameters, including stable body weights, well-groomed coats, and values for total serum protein, serum creatinine, and hematologic parameters that were within reference ranges for the species. There were improvements in the impalas' psychological parameters, which included a decrease in the number of aggressive interactions (head butting and ramming) and an increase in the number of reciprocal allogrooming interactions. The monitored welfare indicators suggest adaptation to captivity. The study showed that impala could be successfully managed in captivity for 16 wk. However, scientific methods (namely darting) increased the risk of injury and caused fatalities.

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.

Comparison of thiafentanil-medetomidine to etorphine-medetomidine immobilisation of impalas (<i>Aepyceros melampus</i>)

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 thiafentanil-medetomidine 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 thiafentanil-medetomidine 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.

Chemical capture of impala (Aepyceros melampus): A review of factors contributing to morbidity and mortality

OBJECTIVE

To review the factors that contribute to morbidity and mortality of impala undergoing chemical capture, and discuss how they are potentially mitigated.

DATABASES USED

PubMed, Science Direct, Google Scholar and Onderstepoort Veterinary Academic Hospital records.

CONCLUSIONS AND CLINICAL RELEVANCE

Impala are an important species of antelope in Africa and are often captured during management procedures, veterinary interventions and research projects. Chemical capture is a preferred technique over physical capture and restraint for veterinary interventions as it allows for easier handling and better clinical assessment and treatment. However, this capture technique results in high mortality (4%) and morbidity rates (23%), which translates into animal welfare and economic concerns. Investigation of environmental, drug and drug delivery, and animal factors to elucidate the origin of these high rates was reviewed. The greatest risks emanate from the drug and drug delivery factors where potent opioids (etorphine and thiafentanil) cause profound respiratory compromise, that if left untreated often translates into fatalities. Furthermore, the procedure of darting, an essential tool in game capture, can cause irreparable fractures and other fatal injuries mainly through accidental misplacement of the dart into a long bone, thoracic or peritoneal cavity. Impala are anxious and flighty, and this demeanour (animal related factor) can contribute towards mortality and morbidity rates. Impala that mount an inappropriate stress response to capture tend to die; therefore, procedures that induce an intense stress response (awake clinical examinations) should be avoided. Sequela of a heightened stress response include capture-induced hyperthermia, myopathies, fractures, maladaptation to confinement or new environments and death. Impala serve as a useful model for improving immobilizing and anaesthetic drug protocols, darting techniques or new methods of remote injection in wildlife. However, the risks associated with chemical capture in this species should be understood, and all efforts to mitigate these should be employed.