Shock in Alpaca During Capture and Chemical Immobilization
The alpaca (Vicugña pacos or Lama pacos) is the smallest relative of the camel. Alpacas are lamoids, a word used to reference several species of South American camelids (Camelidae). This particular group of animals includes llamas, alpacas, vicuñas, and guanacos. Like camels, lamoids are believed to have originated in North America over 40 million years ago, with lamoids migrating to South America and camels migrating east via the Bering Strait, later becoming extinct in North America.1
It is believed that alpacas were developed through selective breeding more than 6,000 years ago by people in the Andes for their wool. Alpacas have slender bodies, small heads, a short tail and large, pointed ears.
Alpacas are the most limited in range and the most specialized of the four species of lamoids, being adapted to altitudes from 13,000 to 15,500 feet.2 Distinguished from llamas (the largest South American camelids) by their smaller size, they are the smallest of the domesticated lamoids. The weight of an adult alpaca ranges from 120 to 150 lbs, with a height ranging from 2 to 3 feet. Alpacas live 15 to 25 years.
Lamoids vary by size and purpose, with some (such as llamas) being used as pack animals and others (such as alpacas) being valued for their fleece.1 The alpaca encompasses two breed types: the huacaya and the suri. Huacayas are the more common type, and account for about 90% of all alpacas.2 The two breed types differ primarily in terms of the properties of their fleece. Alpacas are the most widely-used lamoids for fleece production.
The fleece of the alpaca is lightweight, strong, high in insulation value and very resistant to moisture. It has been reported that during the height of the Incan civilization, the wearing of robes made of alpaca fleece was reserved for the nobility and royalty.3 Alpaca wool fibers are hollow, which gives them the ability to insulate very well, and to absorb moisture. As a result, alpaca farming has become a worldwide industry.
Alpacas are pseudo-ruminants; this means that they have a single stomach that is divided into three compartments instead of four, like other ruminants). They produce rumen, chew cud and are able to process food very efficiently. In the field, alpacas graze on grasses and plants. On farms, alpacas will eat grass or hay. They consume approximately two pounds per 125 pounds of body weight daily in hay or fresh pasture. Some farmers feed extra alfalfa to alpacas that are leaner, or those which live in very cold temperatures.3
What is Shock?
Alpaca management, research and farming often require the chemical immobilization of individual animals. Unfortunately, this can lead to a variety of capture‐induced risks while these animals are chemically immobilized, including shock. Shock is a critical condition that is brought on by a sudden drop in blood flow throughout an animal’s body. It can be the result of a variety of conditions or circumstances, including:
- Extreme physical stress
- Trauma
- Disease
- Heatstroke
- Blood loss
- Allergic reactions
- 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.
The processes surrounding capture or chemical immobilization can include physical stress sufficient to induce shock in animals. The degree of risk depends 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 agentsinvolved in immobilizing the animal and others.
There are two recognized 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. It is of nervous origin, transient in nature, causing widespread capillary paralysis. In the case of wild or timid animals, due to restraining or compulsory exercise, this condition may develop.4
Secondary shock. This can be fatal due to its severity. In secondary shock, 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 leading to lack of availability of blood for pumping out through heart.4
The three categories of shock are as follows:
Circulatory Shock. This occurs when there is a 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 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 In this context, 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 immobilization events.
How Shock Occurs in Alpaca
Practically all of the drugs that produce sedation or anesthesia endanger cardiovascular stability by producing dose-dependent impairment of cardiac function, vascular reactivity and autoregulatory responses.6 Hemoglobin is a substance in the blood that carries oxygen to tissues, and it is found within the red blood cells. Normally, the amount of oxygen delivered to the cell is 2 to 4 times the amount required, which ensures an adequate supply.5 If tissues are not adequately perfused with blood however, the oxygen fails to get to the cells, regardless of the oxygen content in the blood.6
Significant changes in the mean arterial pressure (MAP) 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 typically 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 is a chief factor in stroke volume and cardiac output.6 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.4
Despite their size, camelids (camels, llamas and alpacas) are often agreeable when it comes to handling, thus sedatives and anesthetics are easily administered in order 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 alpaca anesthesia, and it is also recommended that alpacas be orotracheally intubated for procedures lasting more than 20 minutes.9
Diagnosis and Treatment of Shock in the Alpaca
Clinical signs of shock in alpaca can include any combination of the following:
- Unresponsiveness
- Hypothermia
- Tachycardia
- Bradycardia
- Tachypnea
- Bradypnea
- Marked hypotension
- Cyanosis
- Orthopnea
The treatment of shock in alpaca 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 If possible, an intravenous catheter may be placed for vascular access. If venous access cannot be established, an intraosseous catheter can be placed. Oxygen supplementation can also provide benefits to the alpaca experiencing shock. This can be accomplished via flow-by oxygen, mask, nasal cannulas or an oxygen cage.6
Concerning fluid therapy, lactated Ringer’s solution, Normosol-R, and Plasma-Lyte are the preferred choices for resuscitation, as these have been shown to cause fewer complications as well as decrease the risk of mortality4 as compared to other options.
Hypertonic saline is also a preferred option for increasing vascular volume. This increases plasma osmolarity; in other words, pulling water into the vascular space from the interstitial space, thereby expanding plasma volume. It should be noted that hypertonic saline has unwanted side effects, such as a transient, dose-dependent increase in sodium and chloride.4,5 The administration of blood products is an also important adjunct for the treatment of shock in alpacas.5
4Kulkarni, M.D., et. al. Clinico-Pathological aspects of Shock. Veterinary World, Vol. 2(4):163-165, April 2009.
6Noel-Morgan, J., Muir, W. (2018) Anesthesia-Associated Relative Hypovolemia: Mechanisms, Monitoring, and Treatment Considerations. Frontiers in Veterinary Science, Vol. 5 (53).
7Haller G, Laroche T, Clergue F. Morbidity in anaesthesia: today and tomorrow. Best Pract Res Clin Anaesthesiology (2011) 25(2):123–32.
8Steadman 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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