Vomiting in Eld’s Deer During Capture and Chemical Immobilization

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

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

The Elegant Eld’s Deer

Eld's deer (Rucervus eldii) are indigenous to Southeast Asia. So named because of their discovery by Lt. Percy Eld in the Manipur Valley of India in 1838, there are three recognized subspecies of R. eldii. These include:

• Rucervus eldii eldii (native to Manipur),
• Rucervus eldii thamin (native to Burma/Myanmar), and
• Rucervus eldii siamensis, (native to Thailand, Annam, and Hainan island).

The Eld’s deer is a large deer that is considered very regal and graceful in appearance. They are similar in size to white-tailed deer, but differ somewhat in appearance. Their legs are long and thin, and they have slender bodies with a large head and ears. Their rough coats change color with the season. In summer, they are reddish-brown, and dark brown in winter. Stags often have darker coloring than hinds (females) and have a thick mane of long hair around the neck.¹

Eld’s deer stags have large bow- or lyre-shaped antlers; these sweep back in a curve of about 40 inches in length. One smaller tine grows toward the front of the head. Antlers are shed every year and reach their largest size during the breeding season.² Male Eld’s deer grow to about 71 inches in length and weigh from 276 to 386 pounds. They are taller and larger than the hinds, which stand about 60 inches tall.

In their native ranges, Eld’s deer inhabit suitable forest habitats, lowland valleys and plains, avoiding dense forests and coastal areas. This also includes monsoonal forests. Today, they occur in a number of protected areas throughout these areas and have been introduced to numerous countries as game animals, including the United States.²

Eld’s deer are associated with areas that are seasonally burned, and are fond of eating new grasses as they emerge after fires. Their diet consists largely of grasses, fruits, herbaceous and wetland plants. They are known to graze and to browse opportunistically on cultivated crops such as rice, lentils, maize and peas. On ranches and reserves, Eld’s deer are typically fed a low-protein herbivore diet and alfalfa hay.^1,3

Eld’s deer females can begin reproducing at two years of age and typically continue to do so until they are 10 years of age. They begin estrus in the late winter or early spring and have a long period of ovarian activity (225 to 342 days), during which they average 10 to 17 estrous cycles. After they have mated, the females enter anestrus, which usually occurs in the autumn months.²

Rucervus eldii are primarily nocturnal deer. Throughout most of the year, stags tend to be loners, except in the spring when mating commences. Females are generally found alone or in pairs with their young. They remain in close association with their fawns and other female-fawn pairs. Larger groups are often formed when males join groups of females prior to the breeding season, and groups of up to 20 animals are common.

Emesis Risks in Eld’s Deer

As indicated above, anesthetic aspiration involves an Eld’s deer vomiting food from its stomach during a surgical procedure, which subsequently infiltrates into the lungs. This complication 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).”⁴ 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 (called 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.⁴

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 Eld’s deer.

Improvements in Protocols and Immobilizing Drugs

The medical care of non-domestic hoofstock 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.⁵ As a result, research and wildlife veterinarians must have the requisite knowledge associated with safely anesthetizing and handling these animals.

The sedation and anesthesia of Eld’s deer requires the knowledge the pharmacology of the drugs being used, as well as the 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.^4,5 For example, an anesthesia protocol that’s practical in a fenced captive environment may not be appropriate in a free-ranging field environment or large enclosure.

Today, the quality of sedation, anesthesia and analgesia achievable in Eld’s 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 Anesthetic Aspiration in Eld’s Deer

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.¹ 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 an Eld’s deer, the first step in successful management is the immediate recognition of gastric content in the oropharynx or the airways.⁴ 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 deer’s 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.^4,6

¹animaldiversity.org.
²nationalzoo.si.edu.
³animalia.bio.
⁴Nason, K. Acute Intraoperative Pulmonary Aspiration. Thoracic surgery clinics vol. 25,3 (2015): 301-7.
⁵Lance, W. Exotic Hoof Stock Anesthesia and Analgesia: Best Practices. In: Proceedings, NAVC Conference 2008, pp. 1914-15.
⁶Kluger M.T., et. al. Crisis management during anaesthesia: regurgitation, vomiting, and aspiration. Quality & safety in health care. 2005;14(3): e4.