Shock in Dromedary Camels During Capture and Chemical Immobilization
The dromedary camel (Camelus dromedaries) is an even-toed ruminant that occupies the arid regions of the Middle East and northern Africa through northern India. These animals have been so widely domesticated that wild dromedary camels are generally understood to be extinct. There are two main species of camel: the dromedary camel (also called the Arabian camel) and the Bactrian camel (Camelus bactrianus). The dromedary camel has a single hump, while the Bactrian camel (which is native to east Asia and China) has two humps.
Dromedary camels have a long, curved neck and a deep chest. Their single hump is composed of fat and fibrous tissue, which allows the camel to store energy when food is scarce.1 Thus, the size of the hump will vary based on the camel’s nutritional status; the hump becomes smaller during times of scarcity. Dromedary camels can go a week or more without water, and they can last for several months without food.
Camels are ruminants, but they differ from other ruminants in a few significant ways: Camels have a three-chambered digestive tract rather than a four-chambered one. Their upper lip is split in two with each part being separately mobile, which allows for their consumption of hard-to-access, tough, thorny plants. Their oval-shaped red blood cells help to facilitate blood flow when the animal is dehydrated. The camel’s red blood cells are also able to withstand high osmotic variation without rupturing when these animals drink large amounts of water (which can be up to 30 gallons at a time).2,3
Dromedary camels have a number of other adaptations that suit them to desert life. A double row of long eyelashes protects their eyes from blowing sand and dust. During sandstorms, they have the ability to close their nostrils to prevent sand from entering the respiratory tract.2 These camels are able to fluctuate their body temperature throughout the day, which allows them to conserve water by not sweating as the ambient temperature increases.
Dromedary camels are seasonal breeders, with breeding occurring the winter and into the rainy season. Their gestation period lasts for approximately 15 months, followed by the birth of a single calf or, occasionally, twins. Female dromedary camels reach sexual maturity around three years of age, and are able to mate at age four or five. Males do not reach full sexual maturity until age six.2,3
Shock as a Complication of Capture
Shock is a critical condition that involves a sudden drop in blood flow throughout an animal’s body. This can be the result of a variety of circumstances, including extreme physical stress, trauma, disease, heatstroke, blood loss, allergic reactions or severe infection. When an animal is in shock, its organs are not receiving an adequate amount of blood or oxygen. If untreated, this can lead to permanent organ damage or death.
Camel management and research often requires chemical immobilization. Unfortunately, this can lead to a variety of capture‐induced risks while these animals are chemically immobilized, including shock. The degree of risk is contingent upon factors such as sex, age, overall health, environmental factors, length of immobilization, the degree of stress involved in the capture/immobilization event and the specific chemical agents involved in immobilizing the animal.
Dromedary camels were introduced into Australia in the 1840's to assist in the exploration of inland Australia. Today, there are over one million feral camels in the rangeland ecosystems of Australia; these account for the only “wild” dromedaries in existence. Unfortunately, these animals are now causing significant damage to the natural environment. As a method of control, radio-collared camels are being used to enhance population control programs, which involves immobilizing individual camels.4 This procedure carries the risk of a variety of complications in the immobilized animals, shock being among them.
There are two types of shock, and these are divided into three categories. The two types of shock are:
Primary shock (or traumatic shock). This type of shock develops immediately after injury, trauma or extensive surgical wounds during operation and massive handling of internal abdominal organs. Primary shock is serious but tends to be transient in nature.3
Secondary shock. This can be fatal due to its severity. Here, there is disproportion between the volume of blood and volume of blood vascular space. Sufficient blood is not present to fill the blood vessels and to maintain the blood pressure. This leads to lack of availability of blood for pumping out through heart.3
The three categories of shock are:
Circulatory Shock. This type of shock occurs when there is a decrease in effective circulating blood volume. The 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 the body is unable to maintain the vasoconstriction of blood vessels.4
The remaining 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.4,5 The types of shock being discussed are circulatory shock and hypoxic shock, which are the most likely to be brought on due to capture and/or immobilization events.
Chemical Immobilization and Shock
The vast majority of the drugs that produce sedation or anesthesia endanger cardiovascular stability by producing dose-dependent impairment of cardiac function, vascular reactivity and autoregulatory responses.5 Hemoglobin is found within red blood cells and carries oxygen to tissues. Normally, the amount of oxygen delivered to the cell is 2 to 4 times the amount required, depending on the tissue, 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.6
Changes in the mean arterial pressure (MAP) can trigger changes in heart rate.4,5 An increase in MAP causes bradycardia and vasodilation, while a decrease produces tachycardia and vasoconstriction.2 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 generally placed on effects impacting venous physiology and venous return.5
Approximately 70% of a camel’s total blood volume is represented by venous circulation and is a chief contributor to stroke volume and cardiac output.6 Vasodilation is the primary cause of hypovolemia produced by anesthetic drugs. This is often associated with increased venous compliance, decreased venous return, and reduced response to vasoactive substances.4 Contingent upon factors like patient status and monitoring, a state of relative hypovolemia can remain clinically undetected for protracted periods of time.4-6
Due to the extent of their domestication, dromedary camels are often agreeable when it comes to handling, thus sedatives are often used to provide immobility and analgesia. General anesthesia techniques are similar to those for ruminants and horses.1,2 Monitoring core body temperature is essential in camel anesthesia.4 It is also recommended that camels be orotracheally intubated for procedures lasting more than 20 minutes.8
Diagnosis and Treatment of Shock in Dromedary Camels
Clinical signs of shock in dromedary camels may include any combination of the following:
- Marked hypotension
The treatment of shock should center 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 Oxygen supplementation can also provide benefits to a camel experiencing shock. This can be accomplished via flow-by oxygen, mask, nasal cannulas or an oxygen cage.6
Lactated Ringer’s solution, Normosol-R, and Plasma-Lyte are the preferred fluid therapy choices for resuscitation, since these have been shown to cause fewer complications, as well as decreasing the risk of mortality4 compared to other options.
The administration of blood products is an important adjunct for the treatment of shock.5 Hypertonic saline is also a widely used option for increasing vascular volume. This increases plasma osmolarity, pulling water into the vascular space from the interstitial space, thereby expanding plasma volume. Hypertonic saline does have some unwanted side effects however, such as a transient, dose-dependent increase in sodium and chloride.4,5
3Kulkarni, M.D., et. al. Clinico-Pathological aspects of Shock. Veterinary World, Vol. 2(4):163-165, April 2009.
5Noel-Morgan, J., Muir, W. (2018) Anesthesia-Associated Relative Hypovolemia: Mechanisms, Monitoring, and Treatment Considerations. Frontiers in Veterinary Science, Vol. 5 (53).
6Haller G, Laroche T, Clergue F. Morbidity in anaesthesia: today and tomorrow. Best Pract Res Clin Anaesthesiology (2011) 25(2):123–32.
7Steadman 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).
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