Zoo Animal and Wildlife Immobilization and Anesthesia
Strictly speaking, exotic animal medicine encompasses all zoo animals, wildlife, and nondomestic pets,1 and the modalities of treatment for zoo animals and wildlife are nearly identical. This of course includes physical as well as chemical immobilization.
Anesthesia for veterinary patients was first described in the early 1900s. Over time, the importance of providing analgesia has become more apparent. The American College of Veterinary Anesthesia (ACVA) was founded in 1975 and provided a means for board-certifying veterinarians who performed a residency in anesthesia.1 More recently, the ACVA updated its title to the American College of Veterinary Anesthesia and Analgesia, highlighting the increased awareness of the importance of analgesia among veterinary specialists.
General and Regional Anesthesia
The type of anesthesia administered to zoo animals and wildlife depends on a number of factors, including the type of procedure, the animal’s age and medical history. Occasionally, the veterinarian will determine that more than one type of anesthesia will be appropriate for a certain procedure.
General anesthesia places the entire body, including the brain, into a state of unconsciousness, during which the animal has no awareness and feels nothing. General anesthesia is administered by injection or through a breathing mask, or sometimes both. In order to control the animal’s breathing during a surgical procedure, the animal is intubated, which is the insertion of a flexible tube down the windpipe. The tube is inserted after the anesthesia is given and removed when the animal begins waking up and breathing adequately.2
Regional (or Local) Anesthesia involves the injection of a local anesthetic around major nerves or the spinal cord to block pain from a large region of the body, such as a limb. Regional anesthesia provides muscle relaxation as well as postoperative pain relief since its numbing effects can last 8 to 12 hours, depending upon the dose. This reduces the need for pain medication after surgery, as well as other side effects of surgery, such as nausea.2
Some veterinary procedures need to be performed with the animal under general anesthesia (for example: dentistry, surgery, and some diagnostic imaging).3 Most healthy exotic species, even older animals, don’t have any problems with anesthesia and, in general, the risks are more closely related to the procedure being done and the animal’s general health than to the anesthesia itself.
Like any medical procedure, general anesthesia does have risks. These risks can run from minor problems, such as mild vomiting after recovery from anesthesia, to life-threatening problems such as cardiac arrest or stroke. Anesthesia-related deaths are rare, though, and while complications can occur, the veterinarian and his/her team take all of the necessary precautions to ensure that the animal is safe and can handle anesthesia.3
The risks of anesthesia should always be considered along with the benefits, and the risks and benefits of any alternatives to anesthesia should also be considered. In an emergency or life-threatening situation, the risks of anesthesia are usually minimal compared to the risks of not performing the emergency procedure.3
Regional Anesthesia in Exotics – Small Animals
In veterinary medicine, regional anesthesia is used for many reasons, including improved postoperative pain control, decreased systemic opioid use, and improved quality of recovery. Most regional anesthetic techniques used at this time have been adapted from human medicine. However, veterinarians face limitations and challenges that are oftentimes not encountered in the practice of adult human medicine. First, since wildlife and zoo animals are nonverbal, they cannot communicate their degree of pain or the efficacy of an analgesic technique that has been employed. Veterinary medical professionals must rely on various assessment tools to estimate the degree of pain. Another challenge is that of patient compliance.4
There are wide variations in exotic species’ anatomy, physiology, and the pharmacokinetics of local anesthetics that must be taken into consideration prior to safely performing regional anesthesia. Regional anesthesia in feline patients, for example, can be more challenging than regional anesthesia in canine patients. Felines have increased sensitivity to local anesthetics when compared with other species, necessitating much lower maximum doses be used.5,6
Regional Anesthesia in Exotics – Large Animals
Regional anesthesia for large animal species has been practiced for many years. This is largely due to what veterinarians and researchers have learned regarding general anesthesia for large animals. “A general anesthetic event for a horse, for example, requires specialized equipment and carries a much higher risk of complications such as long-bone fractures, myopathy, and neuropathy simply based on sheer size. Equine anesthetic mortality is reported to be 10- to 20-fold greater than for dogs and cats.”5 For these reasons, large animal surgical procedures are typically performed under sedation with regional anesthesia.
Regional anesthesia is not as widely used among exotic species, the exception being in the zoo setting.1 This is in part because pain control in animals that have evolved to mask pain and weakness is a challenge; in the case of wildlife in the field, underlying conditions that cause an animal pain may not be revealed to the veterinarian without comprehensive examination (which is difficult enough itself in the field).5 “Recognizing signs of pain can be difficult when dealing with the gamut of patients from predators to prey species—all of which may express discomfort very differently. Knowledge of the species, specific patient history, and astute powers of observation are invaluable in the development of an analgesic plan.5 In the zoo setting, input from the animal’s primary caregivers, the zookeepers who are attune to subtle changes in behavior, are often the only clue to discomfort in some species.1
Analgesia for Zoo Animals and Wildlife
The zoo veterinarian is frequently called upon to plan and administer analgesia for a wide range of species. He or she must not only recognize and interpret signs of discomfort in these species, but must also determine and implement effective analgesic regimens that accommodate patient and caregiver safety. “Many zoo animals are large, dangerous animals that cannot be approached directly without a barrier or immobilization. However, while that approach may be necessary for a large carnivore such as a lion or tiger, the veterinarian also must be ready to treat something as small as a poison dart frog.”1
Because of the range of species involved in the zoo setting and in wildlife habitats (from whence zoo animals come), there is little evidence-based analgesic information available for most zoo animals.1 Pharmacokinetic studies and analgesia efficacy experiments are rare in the field of zoo medicine. “To get around this, clinicians will use allometric scaling when feasible, adjusting the dosage of a drug to a species based on variations in metabolic rate. For instance, the dosage of opioid in a mouse may be up to 100 times greater than that of an elephant. More often, veterinarians extrapolate from dosages in related species, consult with colleagues, or rely on previous experience to determine what course to follow.”3
A significant concern for the zoo veterinarian is being able to provide analgesia safely. Anesthesia of a fractious or dangerous animal is sometimes the only means to be able to handle some individuals. “However, immobilization/general anesthesia may be contraindicated for very ill, pregnant, or nursing animals and chronically ill patients. One very important addition to the arsenal of treatment strategies that has revolutionized the approach to zoo veterinary care is the use of behavioral training to facilitate treatment.”3
1Schroeder, C., DVM, et. al. Regional Anesthesia and Pain Management in Veterinary Medicine. American Society of Regional Anesthesia and Pain Medicine Journal, Feb. 2017.
4Boscan P, Wennogle S. Evaluating femoral-sciatic nerve blocks, epidural analgesia, and the use of regional analgesia in dogs undergoing tibia-plateauleveling-osteotomy. J Am Anim Hosp Assoc. 2016;52(2):102–108.
5Loughran CM, Raisis AL, Haitjema G, Chester Z. Unilateral retrobulbar hematoma following maxillary nerve block in a dog. J Vet Emerg Crit Care. 2016;26:815– 818.
6Perry R, Moore D, Scurrell E. Globe penetration in a cat following maxillary nerve block for dental surgery. J Feline Med Surg. 2015;17(1):66–72.
7Campoy L, Martin-Flores M, Ludders JW, Gleed RD. Procedural sedation combined with locoregional anesthesia for orthopedic surgery of the pelvic limb in 10 dogs: case series. Vet Anaesth Analg. 2012;39(4):436–440.
8Dugdale AH, Taylor PM. Equine anaesthesia-associated mortality: where are we now? Vet Anaesth Analg. 2016;43(3):242–255.
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
The information contained in this blog post is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the medications shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular medication. You should consult your veterinarian about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the medications to diagnose, cure or prevent disease. Medications compounded by NexGen Pharmaceuticals are prepared at the direction of a veterinarian. NexGen Pharmaceuticals compounded veterinary preparations are not intended for use in food and food-producing animals.
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