Cardiac Arrest in Barasingha Deer During Capture and Chemical Immobilization

Barasingha Deer Background

Deer are among the most well-known of the large wildlife species, and are popular among hunters and wildlife enthusiasts alike. Deer belong to the order Artiodactyla and the family Cervidae, a group also known as cervids. Deer live in almost every country of the world; there are around a half dozen species that are common in North America, as well as various subspecies and non-native species.

The barasingha deer (Rucervus duvaucelii) is a deer species that is distributed across the Indian subcontinent. In its native range, it is also known as the swamp deer. In the late 1960s, the total population of barasingha deer was estimated at less than 4,000 individuals in India and Nepal. The losses leading up to this point were primarily due to overhunting, disease and the conversion of large grassland areas into cropland.⁴ Today, there are large fragmented populations in northern and central India, and the barasingha has been introduced into several countries.^2,3 In the U.S., this deer may be hunted on carefully-controlled ranches and reserves.

The barasingha differs from other deer species in India in that its antlers have more than three tines. It is from this feature that the deer derives its name, which loosely translates into "twelve-horned" in Hindi. In fact, mature stags often have 10 to 14 tines, and some have been known to sport up to 20.³

The barasingha is a relatively large deer; it has a shoulder height of approximately 45 inches and an overall length of nearly 6 feet. Stags weigh from 350 to 630 lbs., and females weigh from 290 to 320 lbs. Some larger stags have been reported as weighing up to 570 lbs.¹ The barasingha deer’s coat is woolly and yellowish brown with white spots along its spine. Its throat, abdomen, inside of the thighs and beneath the tail is white, and its coat becomes a brighter orange-brown color in summer. The females are a bit paler in color than males, and the young have faint spots.²

Barasingha deer are grazing animals with a diet primarily consisting of grasses and aquatic plants. During the day, they feed with peaks during the mornings and late afternoons. In India, herds comprise from 8 to 20 individuals, and larger herds may have up to 60 individuals. During the rut, barasingha deer form large herds of adults. Their breeding season lasts from September to April, and fawns are born after a gestation period of approximately 245 days in August through November.^3,4

Responding to Cardiac Arrest in Barasingha Deer

In zoos and farms, deer may be handled in drop-floor or hydraulic squeeze chutes. Free-ranging deer are sometimes captured with net guns, drive nets, or clover traps.⁴ In the field, remote drug delivery via dart is the method of choice for chemical immobilization. Darts are typically delivered from the ground, a ground-based vehicle or from a helicopter. In a captive situation (e.g., a zoo or farm), drugs may also be delivered via pole syringe or blow dart.

Immobilizing drugs facilitate the transport of barasingha deer and help to decrease stress in captured animals. Chemical immobilization is usually induced with opioids, α2-agonists combined with dissociative drugs⁴ or custom compounded preparations. Neuroleptic drugs should be used with caution, but can be useful in the management of wild and semi-domesticated deer.

Capture and/or chemical immobilization can result in CPA events in barasingha deer, particularly under field conditions. In some instances, the stress of capture can significantly increase the likelihood of cardiac arrest in these animals. While under anesthesia, common causes of CPA can include vagal stimulation, unstable cardiac arrhythmias, severe electrolyte disturbances, exacerbated cardiorespiratory disorders (e.g., congestive heart failure, hypoxia)¹ or a variety of comorbidities. The techniques for cardiopulmonary cerebral resuscitation in barasingha deer involve three stages:

1. Basic life support (BLS)
2. Advanced life support (ALS)
3. Post resuscitation care⁵ 

 Stage 1. This involves establishing an open and clear airway, providing assisted ventilation, and performing chest compressions. If a deer’s pulse becomes absent or weak, all administration of immobilizing drugs must be suspended and external cardiac massage should be initiated. Veterinary patients can usually be easily and safely ventilated with a bag-valve mask,¹ the caveat being that this may not be available under field conditions.

Stage 2. Venous access can be established by using such methods as intraosseus catheter placement and venous cutdown, in which a small opening is created in a vein to allow passage of a needle or cannula.¹ Epinephrine at 0.2 mg/kg (concentrated at 1/10,000) should be given IV or intracardially (IC) while cardiac massage continues. If the deer fails to respond, 0.1 ml/kg IV or IC calcium chloride may be given. If there is still no response, the epinephrine and calcium chloride may be re-administered with 10-20 mEq IV or IC sodium bicarbonate.^5,6

Stage 3. Barasingha deer that are restored to a perfusing cardiac rhythm may experience rearrest, especially if the original cause of the CPA event has not been identified. Therefore, resuscitated animals should have cardiovascular and ventilatory support during the period following CPA. Mild hypothermia after resuscitation from CPA decreases cerebral oxygen demand and has been shown to improve outcomes.⁷

¹Caulkett, N., Arnemo, J. Cervids. Zoo Animal and Wildlife Immobilization and Anesthesia, Second Edition, 25 July 2014.
²worlddeer.org.
³animalia.bio.
⁴animaldiversity.org.
⁵vetfolio.com.
⁶Pablo L.S. Current concepts in cardiopulmonary resuscitation. World Small Anim Vet Assoc World Congr Proc:2003.
⁷Kreeger T., Arnemo, J., Raath, J. Handbook of Wildlife Chemical Immobilization, International Edition, Wildlife Pharmaceuticals, Inc., Fort Collins, CO. (2002).