Vomiting in Barasingha Deer During Capture and Chemical Immobilization

Deer include over 40 species of hoofed ruminants belonging to the order Artiodactyla. This order includes numerous species, among them pigs, camelids, deer, giraffe, antelopes, sheep, goats, and cattle.³ Deer belong to the family Cervidae (referenced as cervids), and are noted for having two large and two small hooves on each foot. Deer are native to all continents except Australia and Antarctica, although many species have been introduced outside of their original habitats as game animals. In all but one species of deer, only the males carry antlers; in the reindeer or caribou (Rangifer tarandus), both sexes have antlers.¹

The Barasingha deer (Rucervus Duvaucelii) is one of the most widely-recognized deer of the Indian subcontinent. Also called the swamp deer, it is found mostly in marshy, damp areas, such as reed beds and marshes. They occasionally dwell in open spaces, but this is usually very close to a source of water.

The Barasingha deer is extinct in both Bangladesh and Pakistan, where it once roamed freely. Today, there are fragmented populations in central and northern India, as well as southwestern Nepal.² The name “Barasingha” is derived from the Hindi words for “twelve ends”, referencing this deer’s antlers, which can have from 12 to 20 tines. Barasingha deer have a lifespan of up to 20 years.

The Barasingha is a large, high-legged deer, with a short head and long, broad ears. Larger animals may have an overall length of up to 71 inches (180 cm) and weigh up to 620 lbs (280 kg). Their coats are a yellowish-brown color, which darkens during the winter months. Some individuals have yellowish spots scattered over their coats. The hair around the deer’s neck may be longer, forming a shaggy mane. The Barasingha’s face also has a dark mask.^2,3

In its native India, there are three subspecies of Barasingha:

1. Wetland Barasingha (Rucervus duvaucelii duvacelii)
2. Hard-ground Barasingha (Rucervus duvaucelii branderi)
3. Eastern Barasingha (Rucervus duvaucelii ranjitsinhii)³

In their native range, Barasingha deer have a number of natural predators including the tiger; thus, they have developed an apprehensive, nervous manner and are always on high alert. They have a loud, barking call that they use to signal danger; this is said to be similar to the alarm call of the roe deer. Barasingha deer feed by day, but can also be found resting during the hottest times of the day. In the winter, large herds form, which dissipate during the summer into smaller herds composed chiefly of females and their fawns. During the summer, males live separately from females in small bachelor groups.

Female Barasingha deer are monoestrous, and usually have a single fawn after eight months of gestation. Fawns are weaned at around six months, and the female is ready to breed again about a year after giving birth. Stags reach puberty at two years of age, and females reach puberty at 18 to 24 months.^2,3

In the late 1960s, the numbers of Barasingha deer in India decreased drastically due to hunting, habitat loss and disease. It was brought back from the verge of extinction over several decades through successful breeding programs and conservation practices. Habitat improvement and captive breeding led to a substantial increase in the population.³ Today, their populations are no longer in danger, and the Barasingha has been introduced to many areas; in the U.S., they may be hunted on carefully-controlled ranches and reserves.

Capture-Related Vomiting and Anesthetic Aspiration

Emesis (vomiting) is one of the more common post-sedation and post-anesthesia complications in both domestic and exotic animals. If this occurs once or twice after a surgical procedure, it can be considered normal however, if the vomiting continues, it can be a sign of a more serious emerging complication.

Vomiting that occurs during a surgical procedure is far more serious, as this can pose grave risks to the animal due to anesthetic aspiration. Anyone who has had inpatient surgery will be familiar with the directive advising to abstain from food for a period of time prior to surgery. This is because anesthesia and sedation carry the risk for vomiting during and after a surgical procedure.

Anesthetic aspiration involves an animal vomiting food 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.

Anesthesia-related aspiration involves the entry of liquid or solid material into the trachea and lungs. This can occur when patients without sufficient laryngeal protective reflexes (as a result of sedation or anesthetic agents) regurgitate gastric contents. “Pulmonary syndromes of differing severity can result, ranging from mild symptoms such as hypoxia to complete respiratory failure and acute respiratory distress syndrome (ARDS).”⁵ In extreme circumstances, cardiopulmonary collapse and death can occur. The related pulmonary syndromes can include acid-associated pneumonitis, particle-associated aspiration (airway obstruction) or bacterial infection. Which of these develops depends upon the composition and volume of the aspirate.

Aspiration during a surgical procedure (acute intraoperative aspiration) is a potentially fatal complication with significant associated morbidity. Animals 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.⁵

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

Immobilization Procedures, Improvements and Risk

The medical care of non-domestic hoofstock such as Barasingha deer has become commonplace due to the integration of veterinary medicine into wildlife management programs, zoological collections, exotic animal ranching expansions and the private collection of wildlife species.⁶ As a result, wildlife veterinarians must have the requisite knowledge associated with safely sedating/anesthetizing and handling these animals.

The sedation and anesthesia of Barasingha deer requires knowledge of the pharmacology of the drugs being used, as well as the wide variation in dose response among sub-species of these animals. A challenge 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.^5,6 For example, an immobilization protocol that is practical in a fenced captive environment may not be appropriate in a free-ranging field environment or larger enclosure.

Today, the quality of sedation, anesthesia and analgesia achievable in Barasingha deer 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.

Preventing and Managing Vomiting in Barasingha Deer

For the prevention of anesthetic aspiration in Barasingha deer, 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.⁵ Additionally, prokinetics (e.g., domperidone, metoclopramide, erythromycin and renzapride) promote gastric emptying and are believed to reduce the risk of aspiration.⁶

Should intraoperative aspiration occur in a Barasingha deer, the first step in successful management is the immediate recognition of gastric content in the oropharynx or the airways.⁵ The deer 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.

The deer’s airway should be secured as rapidly as possible to prevent further contamination and to facilitate airway clearance.⁵ 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. Rigid bronchoscopy may be required if particulate matter is present in the airway.^6,7