Exotic Animal Sedation

While most animals ultimately do well with general anesthesia in the hands of a dedicated veterinarian, the fact is that general anesthesia does pose inherent risks, and this is the case in both animal and human medicine. Exotic animals in the wild, in a zoo setting or as companion animals can be less robust than the average pet dog or cat, and some can be quite expensive to obtain.

This being the case, wildlife handlers, zoo keepers and veterinarians often look to alternatives to general anesthesia when surgical procedures are necessary.

Anesthesia is defined as a pharmacologically induced reversible state of amnesia, analgesia, loss of responsiveness, and loss of skeletal muscle reflexes, or more simply “without sensation”. In contrast, sedation is a “drug induced depression of consciousness during which patients cannot be easily aroused, but responds purposefully following repeated or painful stimulation.” (ASA) For the veterinary patient, the anesthetized animal achieves a surgical plane of anesthesia, while the sedated patient does not. Degree of sedation is variable.¹

Sedation vs. General Anesthesia: Pros & Cons

The advantages of sedation over general anesthesia typically focus on patient safety. The comparative safety of sedation over general anesthesia in human patients is well established. A recent study comparing death rates in dogs, cats and rabbits indicated a 2.5 times higher death rate in anesthetized vs. sedated patients. It is extremely likely that sedation can be associated with decreased risk in other species as well; therefore, sedation should be considered in place of general anesthesia whenever possible.¹

Focus on the use of sedation in exotic animals is a direct result of the perception of greater anesthetic risk in these patients, especially in those that are ill or debilitated. Other advantages of sedation include general reduction of anxiety and stress related to disease processes such as respiratory disease, and for diagnostic sampling and therapeutics. For some ill or extremely stressed patients, the risk of handling is moderate to unacceptably high.² In many cases, the risk of handling must be weighed against the risk of foregoing diagnostic testing or procedures, or risk of general anesthesia. For these patients, sedation provides an attractive alternative.¹

Disadvantages of sedation can include incomplete elimination of patient movement, patient semi-awareness, and lack of complete analgesia. Drugs and lower dosages used for sedation are linked with greater patient safety, but are not entirely without risk.

Disadvantages can be overcome with careful dosing and monitoring, effective patient handling and efficient use of analgesics when handing or procedures are expected to produce discomfort.³ The American College of Veterinary Anesthetists (ACVA) has published recommendations for monitoring patients that are sedated without general anesthesia (ACVA recommendations). If the patient is sedated to the point where protective airway reflexes are lost, monitoring should proceed as with a fully anesthetized patient. In general, the goal of monitoring is to “...ensure adequate oxygenation and hemodynamic stability of the obtunded patient.”¹

1. Palpation of pulse rate, rhythm and quality
2. Observation of mucous membrane color and CRT
3. Observation of respiratory rate and pattern
4. Auscultation
5. Pulse oximetry Supplemental oxygen, and endotracheal tube (where applicable) and materials to obtain vascular access should be readily available1

Agents for the Sedation of Exotic Animals

In general, sedatives produce calmness, loss of aggression and loss of alertness which is generally required during transportation. Animals do not get immobilized fully with tranquilizers and can be aroused by slight disturbances. Therefore, they are used primarily as adjuncts to dissociative anesthetics for hastening smoother induction and to reduce the quantity of anesthetic for achieving more effective immobilization.

This combined synergistic effect of tranquilizer and anesthetic 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 For purposes of this discussion, the use of sedatives without anesthetic agents will be primarily addressed.

Sedation of Exotic Mammals

Midazolam is commonly used in human and traditional pet medicine for purposes of pre-anesthesia and sedation. It has a wide margin of safety in many species. When combined with an opioid, effects are synergistic, allowing a reduction of the amount of either drug. Dosages most commonly used are 0.5-10 mg/kg, combined with an opioid (butorphanol, buprenorphine, hydromorphone, other). Effects are variable, from slight decrease in activity to lateral recumbency. Effects appear to be more pronounced in the ferret and in compromised patients, and less pronounced in rats and mice unless higher dose rates are used. These effects are likely related to species variability in response and the varying dose rates suggested for different species/groups. In all cases, patients still react somewhat to handling and noxious stimuli.¹

When midazolam is combined with an opioid, greater sedation and analgesia result.³ It should be kept in mind that use of sedation and manual restraint alone is inappropriate for any procedure expected to produce discomfort. An exception may be in a calm patient with judicious and efficient use of local anesthesia in the form of a local or regional block (see below). In mammals additional sedation can be provided with sub-anesthetic dosages of ketamine, 2-7 mg/kg, or alfaxalone, 1 mg/kg IM. If additional immobilization is essential, low concentrations of inhalant gas can be considered. This combination of drugs for sedation allows overall reduction of required inhalant gases, decreasing risk associated with the use of general anesthesia.¹

Sedative Agents Used for Birds

Dr. Lennox used a combination of midazolam and butorphanol for use in birds. There is very little published information on the use of midazolam in psittacine species. The use of midazolam combined with butorphanol for premedication of birds has been described in veterinary literature since 2001.¹ A single study described use for control of seizures in an orange winged Amazon parrot with an ingested lead foreign body. A number of studies describe use of midazolam in combination with other drugs for anesthesia of guinea fowl and chickens. Butorphanol is an opioid analgesic agent currently considered the most useful agent of its class in avian patients.² Recent research has focused on pharmacokinetics, and has demonstrated safety in selected healthy psittacine species. The author and others use butorphanol at 1-3 mg/kg, in combination with midazolam, at 0.25-1.0 mg/kg for sedation in avian patients. Pharmacologic data for use of midazolam alone or in combination with butorphanol in psittacine species is currently unavailable.¹

Sedative Agents Used for Reptilian Species

In Sedation as an Alternative to General Anesthesia in Exotic Patients, Dr. Lennox shows a marked preference for the use of IV or IM alfaxalone for sedation of reptiles, although there are several other agents commonly used by veterinarians handling exotics. Alfaxalone (Alfaxan) is an injectable anesthetic agent used for IV induction and maintenance of anesthesia in dogs and cats, and has recently been made available in the United States.¹

Alfaxan is labeled for intravenous use only; however the drug causes no irritation or untoward effects if administered extravascularly. Alfaxan is frequently used with pre-medications, including benzodiazepines and opiates. A particularly attractive benefit of alfaxalone is that it can be used as a repeated bolus, or as a constant rate infusion (CRI) as part of total intravenous anesthesia (TIVA). As a CRI, the drug does not accumulate and recovery does not appear prolonged. This is supported by the observation that repeated IV or IM bolus doses in reptiles do not appear to prolong recovery.¹

Injection of sedative and anesthetic drugs in the caudal body-half should be avoided if possible, since some drugs may undergo a hepatic first pass effect, which may be more important for most anesthetic drugs, compared to the more often discussed renal first-pass effect.⁴ Plasma levels and efficacy of anesthetic drugs can be greatly reduced and may require repeated drug administration.³ Historically, the intramuscular route has been recommended as the route of choice for non-vascular administration of sedative drugs in reptiles. However, the subcutaneous route provides a suitable alternative, in particular in animals with reduced muscle mass or if larger volumes of drugs need to be administered. While the onset of effect is often slower following subcutaneous administration, the depth of sedation or anesthesia reached is ultimately similar following intramuscular administration.⁴

¹Lennox, A., DVM. Sedation as an Alternative to General Anesthesia in Exotic Patients. Delaware Valley Academy Veterinary News, March, 2010.

²Balko, J. et al. Advancements in Evidence-Based Anesthesia of Exotic Animals. Veterinary Clinics: Exotic Animal Practice, Volume 20, Issue 3, 917 – 928.

³Sontakke, S., et. al. A Manual on Chemical Immobilization of Wild Animals. European Journal of Wildlife Research, 36 pp 34-41.

⁴Mans, C. Reptile Sedation, Anesthesia and Analgesia. J Vet Pharmacol Ther. 2015.

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.

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