Chemical restraint of native carnivores (Proceedings)
In wildlife medicine, it is often necessary to chemically restrain animals to perform even the most basic procedure. This is certainly true when one is working with members of the Order Carnivora, a large and diverse group of mammals consisting of seven families (Canidae, Felidae, Ursidae, Procyonidae, Mustelidae, Viverridae, and Hyaenidae). It is, therefore, important to be familiar with the variety of immobilizing agents and equipment used in this field, as well as to understand when to use each of them. Because there is some overlap in the situations in which the various drugs and equipment may be used, personal preference and familiarity play a large role in determining which types of immobilization agents and equipment are used. Other factors involved in this decision include: facility design, the species involved, the attitude and behavioral characteristics of the animal, and the physiologic or pathologic condition of the animal.
Considerations for choice of restraint methods include: human safety, animal safety, environmental factors, knowledge and preference, and the preparation/planning involved.
Physical RestraintAlthough physical restraint of native carnivores may be appropriate in some management and medical situations (and will be influenced by the animal's type, temperament, size [generally ≤ 5 kg], and physical/pathologic condition), it does effect patients in various physiologic and psychological ("stress") ways. In addition, physical restraint may precede an anesthetic procedure, especially when the proper use of physical restraint can preclude the use of additional anesthetic agents. To facilitate the physical restraint of nondomestic patients, therefore, one should have access to equipment such as protective gloves, towels, hoop nets, snares, plastic tubes, and ideally, a squeeze cage.
Most native carnivores, especially large (≥ 5 kg), wild, or fractious individuals, or those requiring extensive procedures or surgical manipulation, require chemical restraint. In these cases, pre-immobilization planning is essential for successful chemical immobilization. This involves having trained personnel, appropriate equipment, an equipment check-off list, a check-off list to refer to during the procedure, emergency drug doses calculated, and a preanesthetic assessment of the patient (may be visual/behavioral observations). Human and animal safety issues must also be addressed prior to the chemical restraint of an animal.
Prior to anesthesia, the patient needs to be fasted for appropriate periods (generally 24-48 hours for large, 24 hours for medium-sized, and 12 hours for small carnivores). Also, withhold water for 12 hours in large animals (unless dehydrated) and 2 hours in smaller patients.
Premedication/sedation of animals may have value in some cases, but may be unnecessary in others. Some medications (i.e., diazepam) can be administered PO prior to a procedure, often with beneficial results; results, though can be highly variable. To administer premedications parenterally, though, requires that an animal be handled or darted twice to achieve anesthesia. In some cases, this can result in an excited animal at the wrong time, negating any potential benefit from a sedative. Frequently, the anesthetic sparing effect of some sedatives can be retained by incorporating them with the anesthetic drugs (i.e., administering the drugs simultaneously). Following induction, maintenance of the animal using gaseous anesthetics is often indicated.
Once anesthetized, it is important to monitor cardiopulmonary functions (i.e., pulse oximeter, Doppler blood flow monitor, ECG, etc.) and temperature of the patient. Administering supportive care such as supplemental heat and fluid therapy to anesthetized patients may be required. Recovery of an anesthetized patient should occur in an undisturbed, quiet, dimly lit, secure area that is free from physical hazards. Animals are generally placed in lateral recumbency for recovery. Chemical reversal of the anesthestic agent is generally desirable. Unfortunately, postanesthetic monitoring of native carnivores is generally difficult.