Sedation for Exotic Animals

While inhalant anesthetics remain the “gold standard” for anesthesia in veterinary medicine, there are many circumstances in which the veterinarian will opt for sedation rather than general anesthesia, particularly when exotic species are considered. Often, the reasoning lies in the fact that general anesthesia poses inherent risks even in the best of circumstances. Additionally, exotic species in the wild, in a zoo setting or as companion animals are sometimes presented under greater stress than traditional companion animals in a practice setting.

Veterinarians working with exotic species should establish consistent anesthetic and analgesic protocols to manage cases that require diagnostic or surgical procedures. The animal should receive a thorough examination, including auscultation of the heart and lung(s), prior to any anesthetic procedure. In those cases where auscultation is limited, such as with reptiles, an ultrasonic doppler may be used to assess the heart. ¹

Pre-surgical blood work, which is commonly performed in domestic species, can provide insight into the physiological status of an animal. A complete blood count and plasma chemistry panel should be performed when possible. In cases where blood volume or owner finances are limited, a packed cell volume, total solids, and blood smear can be performed to provide important information regarding the animal's status. ¹

Sedation Pros and Cons

Like general anesthesia, the sedation of exotic species has its advantages and disadvantages, and the veterinarian has to weigh these based on the individual animal, the procedure(s) involved and the circumstances at hand. In general, some of the advantages of sedation over general anesthesia include:

• Incomplete elimination of patient movement
  • Readily available and economical
  • Readily soluble in water, stable in solution with long self-life
  • High therapeutic index
  • Potent (required dose delivered in small volume) and suitable for most species
  • Fast-acting with smooth onset of induction
  • Minimum excitement
  • Non-irritating upon administration via intravenous or intramuscular route
  • Short induction period
  • Good muscle relaxation
  • Minimum depression of physiological variables (heart rates and breathing)
  • Sufficient analgesia at subanesthetic or lower doses
  • Retention of reflexes such as swallowing
  • Effective antidote having minimum side effects
  • Rapid degradation to inactive, non-toxic metabolites
  • Safe to use in pregnant animals
  • Safe for humans on accidental exposure³

Tranquilizing sedatives such as acepromazine, diazepam, xylazine, medetomidine and azaperone produce calmness, loss of aggression and loss of alertness. These are qualities which are favorable if the animal must be transported, since animals do not become immobilized fully with tranquilizers and can be aroused by disturbances. Often these agents are used primarily as adjuncts to dissociative anaesthetics for hastening smoother induction and to reduce the quantity of anaesthetic for achieving more effective immobilization. This combined synergistic effect of tranquilizer and anaesthetic is far greater than the individual effect of either of the two drugs with respect to smooth induction, good muscle relaxation and smoother recovery. ³

Species Variability

Variability in the physiology of exotic species can result in variable responses between classes of animals; anesthetics that provide surgical anesthesia in a mammal or bird may provide little to no anesthesia in a reptile or amphibian. ³ Differences in anesthetic responses within animal classes have also been described. The anesthetic agents that have been found to provide the most reliable results in exotic species include the dissociatives, alpha-2 agonists, propofol and inhalant anesthetics.¹

Ectotherms (such as reptiles and amphibians) should be provided supplemental heat during an anesthetic procedure that is consistent with their preferred environmental temperature. Endotherms, including birds and exotic species of mammals, should also be provided supplemental heat during these procedures. Hypothermia in endotherms can result in the loss of essential energy to maintain an appropriate core body temperature. Animals maintained at an inappropriate temperature will experience a prolonged recovery. ¹ Water-circulating heat pads and forced air heating units provide good results and are unlikely to cause burns. Radiant heat from an incandescent light can also be used to provide supplemental heat.