BAM Chemical Immobilization for Wildlife
Field wildlife anesthesia is often necessary for both invasive and noninvasive procedures. Typically, anesthesia for noninvasive procedures is utilized for the safety of the handlers and animals. Further, anesthesia and analgesia are crucial components of any chemical immobilization protocol. Anesthesia should not be mistaken for simple immobilization and recovery, without regard for the importance of monitoring and maintaining a stable patient during procedures.
Basic definitions associated with chemical immobilization protocols include:
- Anesthesia: Central nervous system depression that provides unconsciousness and immobility in response to painful stimulation. Drugs that produce anesthesia may or may not provide analgesia.
- Sedation: A state of mental calmness, decreased response to environmental stimuli, and muscle relaxation. Sedation is characterized by suppression of spontaneous movement with maintenance of spinal reflexes.
- Analgesia: The absence of pain in response to stimulation that would normally be painful. An analgesic drug can provide analgesia by acting at the level of the central nervous system or at the site of inflammation to diminish or block pain signals.
Challenges in the Field
Some animals may become distressed by handling, increasing the risk of physical damage and of adrenaline release leading to problems under subsequent anesthesia.1 Whenever possible, the animal’s respiratory rate should be recorded before procedures begin or, if trapped prior to immobilizing drugs being administered. The risk of physical damage is considerably reduced by proper handling.
Problems may also arise when anesthetizing certain exotic mammals, which can present unique and varied challenges.2,3Dangerous animals are often impossible to evaluate and examine thoroughly prior to immobilization and/or induction for reasons of human safety. In research, it is particularly important that methodologies have little or no influence on the result of the study.
There are basic principles that apply when using general anesthesia in wildlife in addition to the sound, basic principles of domestic animal anesthesiology. These additional comments are based on the fact that some exotic mammals are often small in size, have high metabolic rates, have high body surface area/volume ratios and are prone to hypothermia.1However, there are solutions that can help address these problems. Those in the field should be mindful that animals under sedation alone should still be carefully monitored.
Improvements in the Chemical Immobilization of Wildlife
Improvement of chemical capture is an important part of wildlife conservation and animal welfare to minimize distress for the animals and the risk of morbidity and mortality, and many improvements in immobilizing drugs and drug combinations have been made since wildlife managers and veterinarians began pioneering these techniques in the 1950s and 1960s.
The efficacy and safety of anesthetic techniques in wildlife have increased greatly, but complications can still occur. Some of these complications are predictable but others, such as hyperthermia, acidosis, and capture myopathy may result from capture events.3 With anesthesia of domestic animals, it is often possible to titrate induction drugs to minimize adverse effects, but during anesthesia of wildlife, drugs are often delivered at the higher end of the dose range in an attempt to induce anesthesia rapidly.2 Opioids are administered during the perianesthetic period to provide sedation and preemptive analgesia prior to induction, and are part of balanced anesthesia, reducing minimal anesthetic concentration of the inhalant anesthetic.
As indicated above, chemical immobilization of wildlife often includes opioids or cyclohexamines. These substances are problematic as a result of their required storage, handling, and record-keeping protocols.
The BAM Formulation
Drug combinations are commonly used to immobilize free-ranging and captive wildlife. In recent years, the refinement of drug combinations has resulted in the development and marketing of several reliable and efficacious formulations, such as the BAM formulation for wildlife.
Photo Credit: Global Wildlife Resources
Butorphanol (butorphanol tartrate) is a synthetically derived opioid agonist-antagonist analgesic of the phenanthrene series, with a potency of about four to seven times that of morphine. In the United States, it is a U.S. Drug Enforcement Administration (DEA) class IV controlled substance. Although it causes fewer cardiovascular effects as compared with the classical opioid agonists, butorphanol can cause a decrease in heart rate secondary to increased parasympathetic tone and mild decreases in arterial blood pressure. However, increased heart rates have been noted in horses after IV injection.4
The risk for physical dependence appears minimal in veterinary patients. Butorphanol is well-distributed, with the highest levels (of the parent compound and metabolites) found in the liver, kidneys, and intestine. Concentrations in the lungs, endocrine tissues, spleen, heart, adipose tissue, and blood cells are also higher than those found in plasma. In humans, ≈80% of the drug is bound to plasma proteins.4
Azaperone is a butyrophenone tranquilizer that causes tranquilization and sedation, antiemetic activity, reduced motor activity, and inhibition of CNS catecholamines. Azaperone has been used as a neuroleptic in horses, but some horses develop adverse reactions (e.g., sweating, muscle tremors, panic reaction, and CNS excitement) and IV administration has resulted in significant arterial hypotension.4
The butyrophenones as a class cause tranquilization and sedation (sedation may be less than with the phenothiazines), antiemetic activity, reduced motor activity, and inhibition of CNS catecholamines (dopamine, norepinephrine). Azaperone appears to have minimal effects on respiration and may inhibit some of the respiratory depressant actions of general anesthetics. A slight reduction of arterial blood pressure has been measured in pigs after IM injections of azaperone, apparently due to slight alpha-adrenergic blockade.4
Medetomidine (medetomidine hydrochloride), used alone and in combination with other drugs, has been shown to be useful for anesthesia and immobilization in zoo animals.4 Medetomidine is an α-2-adrenoreceptor agonist with sedative and analgesic properties. It is used by veterinarians as both a surgical anesthetic and analgesic. The pharmacological restraint and pain relief provided by medetomidine facilitates handling and aids in the conduct of diagnostic or therapeutic procedures.
The adverse effects reported with medetomidine are essentially extensions of its pharmacologic effects including bradycardia, occasional AV blocks, decreased respiration, hypothermia, urination, vomiting, hyperglycemia, and pain on IM injection.4 Rare effects have also been reported, including prolonged sedation, paradoxical excitation, hypersensitivity, apnea, and death from circulatory failure.
The BAM formulation is known to provide a low-volume, reversible alternative to other immobilizing drug combinations. This combination has been widely evaluated in studies for the immobilization of numerous wildlife species.
1Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007, 432 pages.
2Mich, P.M., et. Al. Evaluation of intramuscular butorphanol, azaperone, and medetomidine and nasal oxygen insufflation for the chemical immobilization of white-tailed deer, Odocoileus virginianus. J Zoo Wildl Med. 2008 Sep;39(3):480-7.
3Ellis, C.K., et. al. Comparison of the efficacy of four drug combinations for immobilization of wild pigs. Eur J Wildl Res 65, 78 (2019).
4Plumb’s Veterinary Drugs.
About NexGen Pharmaceuticals
NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.
Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.
Disclaimer
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