Chemical Immobilization: Medical Emergencies 3 - Bloat, Seizures, Injury, Pneumonia & Offspring
Capture and/or chemical immobilization events carry inherent risks to wildlife regardless of size or species, but these risks are often more pronounced when dealing with larger species, particularly in the field. Included in these risk factors is the potential for an animal to be injured during a chemical immobilization event.
The San Diego Zoo Wildlife Alliance (SDZWA) offers courses in safe capture chemical immobilization techniques for those who are interested in or who are pursuing careers in veterinary medicine, wildlife management, biology, zoology, animal control or continuing education credit. The purpose of these programs is to provide guidance regarding the safe chemical immobilization of animals, thereby reducing the likelihood of complications. One of the modules in this series is Chemical Immobilization: Medical Emergencies 3 - Bloat, Seizures, Injury, Pneumonia & Offspring.
Bloat
Bloat is a serious condition that is fatal if left untreated. This can occur when an animal's stomach fills with gas, food, or fluid and subsequently twists. In instances of bloat, it is the twisting and flipping of the stomach that creates a life-threatening condition. When the stomach becomes severely distended with gas, fluid or food, it puts pressure on the surrounding organs and decreases blood flow to and from these organs. The twisted stomach completely obstructs blood supply to major organs and can impact blood flow throughout the whole body, resulting in shock.1
If an immobilized animal starts to bloat, all administration of immobilizing drugs should be suspended. The animal should be re-positioned into sternal recumbency with the neck extended and the head with the nose pointing down. Intubation of the animal to relieve gases inside may be done; in some cases, trocharization of the rumen is recommended.1 If the veterinarian has high confidence that the bloat is being caused by the anesthetic agents, he or she may employ the available reversal agents to antagonize their effect.1,4
Seizures
While seizures during chemical immobilization can occur spontaneously in some animals, they are more often the result of the immobilizing agent(s) being used. Ketamine hydrochloride is one of the most widely-used dissociative anesthetics in veterinary medicine, and one of the most versatile drugs for animal immobilization and capture. It is used singly and in combination with formulated drugs, but it has been known to cause seizures in animals when used alone. Seizures have been reported in wild cats and non-domestic cats with the use of ketamine.
If an immobilized animal suffers a generalized seizure, all administration of immobilizing drugs should be suspended. If ketamine has been used, it can be antagonized with yohimbe hydrochloride. If the seizure is spontaneous, the veterinarian may employ other anti-convulsive drugs.
Injuries
When an animal suffers a wound during capture/chemical immobilization, ethical imperatives dictate that those undertaking the required research or wildlife management protocols make every effort to ensure that the animal is promptly treated so that it can make as complete a recovery as is possible.
The first step will be to clean the wound. In the case of small, shallow lacerations, this can be done by flushing with a commercial povidone-iodine or other scrub solution. Deeper wounds can be flushed with povidone-iodine diluted with saline, and should generally not be sutured to allow for drainage.3 The current literature recommends high volume and, ideally, high-pressure irrigation unless the tissue is very delicate.4 For suturing more superficial wounds that have been cleaned, a veterinarian should perform the procedure. If a veterinarian is not immediately available, non-absorbable sutures should be used.
Any animal receiving a laceration prior to or during an anesthetic event should receive systemic antibiotics to reduce the likelihood of infection.
Pneumonia
Bacterial pneumonia in chemically immobilized animals is most often associated with aspiration after vomiting due to an immobilization event. When foreign substances such as food, drink, or stomach contents make their way into the lungs, they can significantly damage the lung tissues, resulting in acid-associated pneumonitis.
For the prevention of anesthetic aspiration, the available literature recommends histamine (H2) antagonists such as cimetidine, famotidine, nizatidine, and ranitidine and proton pump inhibitors (PPIs) such as dexlansoprazole, esomeprazole, lansoprazole, omeprazole, pantoprazole, and rabeprazole, which have been shown to be effective in increasing the pH and reduce the volume of gastric contents.2 Prokinetics (e.g., domperidone, metoclopramide, erythromycin and renzapride) promote gastric emptying and are also believed to reduce the risk of aspiration.4
In the event that aspiration occurs during a procedure, the first step in managing the situation is the immediate recognition of gastric content in the oropharynx or the airways.2 The animal should be immediately positioned with the head down and rotated laterally if possible. Orotracheal and endotracheal suctioning is indicated, either before or after orotracheal intubation, depending on whether regurgitation continues and if the airway is visible.
Offspring
Concern are often raised concerning the capture and chemical immobilization of pregnant female animals, since drugs may reduce reproductive output and survival rate of offspring.5 It has been shown that α2-agonists drugs can affect bovine uterine contractility, and these drugs have been reported to cause abortion in horses. There is also growing body of evidence which shows that the perception of predation risk by female animals can affect the fitness of future offspring. The research findings on this subject are conflicting, however; in many species, no negative effect of chemical immobilization has been reported on either reproduction or infant survival.
Given their motivations for hunting, feeding dependent offspring and mating, there are occasions where a target animal will have offspring nearby, or that such offspring may be discovered after the animal has been immobilized. In situations where alternative, noninvasive measures can be used, these should be used.6 While it is generally better to avoid immobilizing an animal with attendant offspring, there are cases (e.g., injury, illness, relocation) where doing may be unavoidable. This may include cases in which a female and her young must all be captured for treatment or relocation.
In the event that an animal with offspring must be chemically immobilized, the young should not be handled unless their capture is also required. Procedures should be carried out as expeditiously as possible to limit the duration that the young are without their mother. Other procedures should be at the discretion of the attending veterinarian or wildlife manager.
Interested in learning more about safe capture? The San Diego Zoo now offers courses in safe capture techniques and best practices. Learn reliable, safe, and effective techniques for the species you work with and the scenarios you encounter!
1Wolfe, B. (2015). Bovidae (except sheep and goats) and antilocapridae. In Miller, R. E., Fowler, M. E. (eds) Zoo and Wild Animal Medicine. (Volume 8). St Louis, Missouri: Elsevier Saunders, 626-644.
2Lance, W. Exotic Hoof Stock Anesthesia and Analgesia: Best Practices. In: Proceedings, NAVC Conference 2008, pp. 1914-15.
3Ball, L. Antelope Anesthesia. Wiley Online Library, 25 July 2014,
4Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007, 432 pages.
5Brivio, F. et. al. (2015) Assessing the Impact of Capture on Wild Animals: The Case Study of Chemical Immobilization on Alpine Ibex. PLoS ONE 10(6): e0130957.
6Thiemann, G., et. al. Effects of chemical immobilization on the movement rates of free-ranging polar bears, Journal of Mammalogy, Volume 94, Issue 2, 16 April 2013, Pages 386–397
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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.
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