Kudu Antelope Vomiting During Capture and Chemical Immobilization

The kudu is a large African antelope that consists of two subspecies: the greater kudu (Tragelaphus strepsiceros), and the lesser kudu (Tragelaphus imberbis). The greater kudu is second in size to the eland, Africa’s largest antelope. Both subspecies have stripes and spots on their bodies and a chevron of white hair between the eyes.¹ The males have long, spiraling horns, with the horns of the greater kudu growing as long as six feet. The females of both subspecies are substantially smaller than the males.

The greater kudu inhabits the dense brush and forested areas of southern Africa, while the more elusive lesser kudu is common in the arid lowland thornbush of northeast and East Africa.² For food, both kudus forage on a wide variety of trees, shrubs, vines, herbs, seedpods, fruits and grasses. Both species prefer the green growth along watercourses in dry seasons and disperse through deciduous woodlands during rainy seasons.¹

Chemical Immobilization and Vomiting in Kudu

The veterinary care of kudu has become commonplace due to the integration of veterinary medicine in wildlife management programs, zoological collections, exotic animal ranching expansions and the private collection of wildlife species.³ As a result, wildlife managers and veterinarians are frequently called upon to anesthetize and handle these animals. Vomiting is one of the more common post-sedation and post-anesthesia complications in both domestic and exotic animals. Vomiting once or twice after a surgical procedure can be considered normal however, if the vomiting continues, it can be a sign of an emerging complication.

Anesthetic aspiration involves an animal vomiting food from their stomach during a surgical procedure, which subsequently infiltrates into the lungs. This can lead to aspiration pneumonia. While modern protocols for anesthesia and sedation in wildlife are generally safe, respiratory complications such as anesthesia-related aspiration and pneumonia can be fatal.

Acute intraoperative aspiration (aspiration during a surgical procedure) is a potentially fatal complication with significant associated morbidity. Kudu undergoing thoracic surgery are at increased risk for anesthesia-related aspiration, largely due to the predisposing conditions associated with this complication. Awareness of the risk factors, predisposing conditions, precautions to decrease risk and immediate management options by the veterinarian is imperative to reducing risk and optimizing outcomes associated with this complication.³

Unfortunately, in the case of chemically immobilized wildlife, it is often impossible to perform the sorts of presurgical assessments that are routine and even required for human and domestic animal patients. Therefore, attending wildlife and research veterinarians must be prepared for the possibility of anesthetic aspiration in kudu.

Mitigating Vomiting Risk in Kudu

The sedation and anesthesia of kudu requires knowledge of the pharmacology of the drugs being used, as well as the wide variation in dose response among subspecies of kudu. A major challenge—and one which impacts potential complications such as anesthetic aspiration—is correlating the available pharmaceutical tools with the environment and conditions, as well as the procedures and events preceding, during, and following the anesthetic event (e.g., an anesthesia protocol that is practical in a fenced captive environment may not be appropriate in a free-ranging field environment).⁵

According to the available literature, each species of antelope has its own anesthesia recommendation with intra-species variations of dosages because of diverse individual responses to anesthetic agents.^4,5 These variations are of course factors in the risk of vomiting and anesthetic aspiration in these species, and attendant factors (e.g., stress, venue, individual animal and field conditions) must also be taken into account. Today, the quality of sedation, anesthesia and analgesia achievable in kudu and other wildlife species has been made possible through the availability of new, receptor-specific and highly potent agonist-reversible pharmaceuticals and the improved knowledge of CNS receptors.

Monitoring core body temperature is essential when anesthetizing kudu and other antelope species.⁵ Hyperthermia and subsequent capture myopathy are commonly-encountered problems with antelope anesthesia. Intubation has been widely recommended for any anesthetized antelope that needs to be transported or anesthetized for greater than one hour. Until the more recent use of formulated drugs (e.g., combinations of α2-agonists such as medetomidine, detomidine, xylazine and their reversal agents), opioids were the mainstay of antelope anesthesia in wildlife and captive care.⁵

Preventing and Managing Vomiting in Kudu

For the prevention of anesthetic aspiration, histamine (H2) antagonists such as cimetidine, famotidine, nizatidine, and ranitidine and proton pump inhibitors (PPIs) such as dexlansoprazole, esomeprazole, lansoprazole, omeprazole, pantoprazole, and rabeprazole have been shown to be effective in increasing the pH and reduce the volume of gastric contents.³ Additionally, prokinetics (e.g., domperidone, metoclopramide, erythromycin and renzapride) promote gastric emptying and are believed to reduce the risk of aspiration.⁵

The first step in successful management of an intraoperative aspiration is the immediate recognition of gastric content in the oropharynx or the airways.³ 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. It is recommended that the airway be secured as rapidly as possible to prevent further contamination and to facilitate airway clearance.⁶ Flexible bronchoscopy is an important adjunct to orotracheal and endotracheal suctioning, and having a flexible bronchoscope at the ready if possible is a sound prophylactic measure. If particulate matter is present in the airway, rigid bronchoscopy may be required.^3,6