Shock in Barasingha Deer During Capture and Chemical Immobilization

There are over 40 species of deer globally. Most of these are found in Asia, although many species have been introduced outside of their original habitats as game animals.¹ There are seven species of deer that are native to North America, with many existing sub-species. Deer have a range that covers the North American continent, making them popular among big game hunters and, more recently, deer farmers. Deer are cervids (family Cervidae), a group of animals belonging to the order Artiodactyla.

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 usually remain very close to a water source. 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.

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.⁴ 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 In the U.S., introduced populations may be hunted on carefully-controlled ranches and reserves.

The barasingha is a large deer with long legs, 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.^3,4

In India, there are three subspecies of barasingha deer:

1. Wetland barasingha (Rucervus duvaucelii duvacelii)
2. Hard-ground barasingha (Rucervus duvaucelii branderi)
3. Eastern barasingha (Rucervus duvaucelii ranjitsinhii)⁴

Barasingha deer have a number of natural predators in their native range. As a result, they have 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.³

Barasingha deer does are monoestrous, and usually give birth to 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.^3,4

Risks of Shock in Barasingha Deer

Shock is a dangerous condition that develops due to a sudden drop in blood flow throughout an animal’s body. It can be the result of a number of conditions or circumstances, including extreme physical stress, trauma, disease, heatstroke, blood loss, allergic reactions or severe infection. When an animal is suffering from shock, its organs are not receiving an adequate amount of blood or oxygen. If untreated, this condition can lead to permanent organ damage or death.

The events surrounding capture and/or chemical immobilization can include extreme physical stress and/or trauma sufficient to induce shock in barasingha deer and other animals. The degree of risk is dependent upon factors such as species, sex, age, overall health, environmental factors, length of immobilization, the degree of stress involved in the capture/immobilization event itself, the specific chemical agents involved in immobilizing the animal and others. It should be noted that cervids are known to be susceptible to a variety of complication during chemical immobilization, including shock.

There are three main categories of shock, which include:

Circulatory Shock, which occurs when there is a significant decrease in effective circulating blood volume. This category is further divided into the three subcategories of cardiogenic, hypovolemic and distributive shock. Cardiogenic shock occurs when the circulating volume of blood decreases despite normal or increased blood volume. Hypovolemic shock occurs when blood volume is decreased through hemorrhage, third space fluid distribution, or dehydration. Distributive shock occurs when an animal’s body is unable to maintain the vasoconstriction of blood vessels.⁵

The last two categories of shock are hypoxic shock and metabolic shock. Hypoxic shock results from impaired oxygen delivery to cells, while metabolic shock involves cells that have become unable to utilize oxygen for energy production.^5,6For the purposes of this discussion, the types of shock being discussed are the subcategories of circulatory shock and hypoxic shock, which are the most likely to be brought on due to capture and/or chemical immobilization events.

The Mechanics of Shock in Barasingha Deer

Even under well-controlled circumstances, chemical immobilization is a risky proposition in barasingha deer. Nearly all of the drugs that produce sedation or anesthesia compromise cardiovascular stability by producing dose-dependent impairment of cardiac function, vascular reactivity and autoregulatory responses.⁶

Hemoglobin is found within red blood cells and carries oxygen to tissues. In normal circumstances, the amount of oxygen delivered to cells is 2 to 4 times the amount required, which ensures an adequate supply.⁵ However, if tissues are not adequately perfused with blood, the oxygen fails to get to the cells, regardless of the oxygen content in the blood.⁵

Significant changes in the mean arterial pressure (MAP) trigger changes in heart rate.^6,7 An increase in MAP also causes bradycardia and vasodilation, while a decrease produces tachycardia and vasoconstriction.^5,6 While anesthesia-related depression of cardiac function and arterial vasodilation are adverse effects that are well-recognized as contributing to anesthetic risk, far less emphasis is usually placed on effects impacting venous physiology and venous return.⁵

Approximately 70% of an animal’s total blood volume is represented by venous circulation, and this is a chief contributor to stroke volume and cardiac output.⁵ Vasodilation is the primary cause of hypovolemia produced by anesthetic drugs. It is often associated with increased venous compliance, decreased venous return, and reduced response to vasoactive substances.⁶ Depending on factors such as patient status and monitoring, a state of relative hypovolemia can remain clinically undetected for long periods of time.^5-7

Diagnosis and Treatment of Shock in Barasingha Deer

The clinical signs of shock in barasingha deer can include any combination of the following symptoms:

• Unresponsiveness
• Hypothermia
• Tachycardia
• Bradycardia
• Tachypnea
• Bradypnea
• Marked hypotension
• Cyanosis
• Orthopnea

The treatment of shock must primarily focus on increasing oxygen delivery to the tissues. This can be accomplished by providing supplemental oxygen, increasing effective circulating volume, increasing hemoglobin concentration and increasing cardiac output with stimulants.^5,7 An intravenous catheter should be placed for vascular access if possible. If venous access cannot be established, an intraosseous catheter can be placed. Oxygen supplementation, when available, will also provide benefits to the deer suffering from shock. This can be accomplished via flow-by oxygen, mask, nasal cannulas or an oxygen cage.⁶

Fluid Therapy for Shock in Barasingha Deer

Lactated Ringer’s solution, Normosol-R, and Plasma-Lyte are the preferred choices for fluid therapy in treating shock in barasingha deer, as these have been shown to cause fewer complications as well as decreasing the risk of mortality⁵compared to other options. Hypertonic saline is also a popular option for fluid therapy (as this increases vascular volume). Hypertonic saline increases plasma osmolarity, pulling water into the vascular space from the interstitial space, thereby expanding plasma volume. It should be noted that hypertonic saline does have unwanted side effects, such as a transient, dose-dependent increase in sodium and chloride.^7,8

Blood products are an important adjunct for the treatment of shock in barasingha and other deer species. In normal individuals, anemia can be well-tolerated with oxygen delivery being maintained. In patients with trauma and acute loss of blood volume however, the associated stressors can contribute to decreased oxygen delivery.⁹

¹britannica.com.
²britannica.com.
³worlddeer.org.
⁴animalia.bio.
⁵wildlifeinformer.com.
⁶todaysveterinarynurse.com.
⁷Noel-Morgan, J., Muir, W. (2018) Anesthesia-Associated Relative Hypovolemia: Mechanisms, Monitoring, and Treatment Considerations. Frontiers in Veterinary Science, Vol. 5 (53).
⁸Haller G, Laroche T, Clergue F. Morbidity in anaesthesia: today and tomorrow. Best Pract Res Clin Anaesthesiology (2011) 25(2):123–32.
⁹Steadman J, Catalani B, Sharp CR, Cooper L. Life-threatening perioperative anesthetic complications: major issues surrounding perioperative morbidity and mortality. Trauma Surg Acute Care Open (2017).