Frostbite in Alpaca During Capture and Chemical Immobilization

The alpaca (Vicugña pacos) is a domesticated member of the camelid family (Camelidae), which also includes llamas, guanacos, vicunas and camels. All except the latter are New World camelids, which are sometimes called lamoids.¹Native to the high altitudes of the Andes of Chile, Peru and Bolivia, alpacas have been kept for their luxurious fleece for thousands of years.

Alpacas are the smallest of the domesticated camelid species. Theyare slender-bodied animals with a long neck and long legs, a short tail, a small head, and large, tapering ears. The weight of an adult alpaca ranges from 120 to 140 lbs, with a height ranging from 2 to 3 feet.

There are two breeds of alpaca, known as huacaya and suri, although they are technically one species.² Over 90% of alpacas are huacayas. Their fleece grows perpendicular to the skin, giving them a wooly appearance. Suris have a straight fleece that curls downward, resembling dreadlocks. Alpaca coats vary in color from black or brown to pale yellow and white. Alpaca wool fibers are hollow, which makes them able to insulate very well, to absorb moisture and wick it away.³As a result, alpaca farming has become a worldwide cottage industry. Alpacas are shorn once a year, usually in the Spring when the weather is warm.

Alpacas are pseudo-ruminants, which means that they possess a single stomach divided into three compartments instead of four, like other ruminants. They are grazers, feeding on grasses from the mountainsides and valleys of the Andes. Alpacas on farms are typically fed a combination of fresh grass and hay.

For short medical procedures on alpaca, withholding food and water may be unnecessary, but for longer procedures or ones that necessitate recumbency, food should be withheld for 24 to 36 hours beforehand, and water should be withheld for 12 hours prior. Bloating can occur in camelids; aspiration of first stomach compartment (C1) contents is known to be a greater risk.⁴

Understanding Frostbite in Alpaca

Frostbite is a freezing injury that may be divided into four overlapping phases: Prefreeze, freeze–thaw, vascular stasis and late ischemic.⁵Prefreeze consists of tissue cooling with accompanying vasoconstriction and ischemia and without ice crystal formation. The freeze–thaw phase is represented by the intracellular or extracellular formation of ice crystals. This can give rise to protein and lipid derangement, cellular electrolyte shifts, cellular dehydration, cell membrane lysis, and cell death. In the vascular stasis phase, vessels fluctuate between constriction and dilation, and blood may leak from vessels or coagulate within them. The late ischemic phase results from progressive tissue ischemia and infarction from a cascade of events, including inflammation, vasoconstriction and emboli.⁵

The normal body temperature for alpaca adults and crias is from 99.5-102 degrees Fahrenheit, although the temperature of newborn crias can run slightly higher. The chemical immobilization of alpaca can require extended periods of immobility in the captured animal. Hypothermia is an inherent risk to any animal undergoing chemical immobilization regardless of the ambient temperature, and frostbite is an even greater risk during the winter months.^6,7

Frostbite Classifications

Frostbite is classified into four degrees of injury which follow the classification system for thermal burns. Early stage frostbite is different than frostnip, which is a superficial nonfreezing cold injury associated with intense vasoconstriction on exposed skin. Frostnip may precede frostbite, however.⁷

• First-degree frostbite causes numbness and erythema. A white or yellow, firm, and slightly raised plaque may develop in the area of injury. There may be slight epidermal sloughing and mild edema is common.
• Second-degree frostbite injury causes superficial skin vesiculation. A clear or milky fluid will be present in superficial blisters surrounded by erythema and edema.
• Third-degree frostbite causes deeper hemorrhagic blisters, indicating that the injury has extended into the reticular dermis and beneath the dermal vascular plexus.
• Fourth-degree frostbite extends completely through the dermis and involves the comparatively avascular subcutaneous tissues, with necrosis extending into muscle and bone.⁷

Preventing Frostbite in Alpaca

Frostbite injury usually occurs when tissue heat loss exceeds the ability of local tissue perfusion to prevent freezing of soft tissues. Since frostbite is usually preventable but often not improved by treatment, frostbite prevention is considered a far better methodology than frostbite treatment. Nascent medical issues and the chemical immobilization event itself can increase the risk of frostbite, so prevention should address both medical and environmental aspects. The team in the field must ensure adequate perfusion and minimize heat loss to prevent frostbite.⁷

Preventive measures to ensure local tissue perfusion include:

• Maintaining adequate core temperature
• Maintaining adequate body hydration
• Minimizing the effects of any known diseases that might decrease perfusion
• Covering the body and head to insulate from the cold
• Minimizing any blood flow restriction
• Using supplemental oxygen in severely hypoxic conditions⁷

Additionally, steps should be taken to minimize exposure of the animal’s tissues to cold, such as:

• Avoid environmental conditions that predispose to frostbite if possible (e.g., below -15°C, even with low wind speeds
• Protecting exposed skin from moisture, wind, and cold
• Avoiding perspiration or wet extremities
• Increasing insulation and skin protection
• Using chemical and/or electric warmers to maintain peripheral warmth (These should be close to body temperature before being activated and must not be placed directly against skin or constrict flow)
• Regularly checking the animal’s temperature
• Recognizing frostnip or superficial frostbite before it becomes more serious
• Minimizing duration of cold exposure⁷

Treatment of Frostbite in Alpaca

If an alpaca’s body part is frozen in the field, the frozen tissue should immediately be protected from further damage.⁷Regarding the thawing of frozen tissue, if environmental conditions are such that thawed tissue could refreeze, it is often safer to keep the affected part frozen until a thawed state can be maintained.

Hypothermia frequently accompanies frostbite and causes peripheral vasoconstriction that impairs blood flow to the extremities. Mild hypothermia may be treated concurrently with frostbite injury. Moderate and severe hypothermia should be treated effectively before treating frostbite injury.^7,

NSAIDs Treatment

Nonsteroidal anti-inflammatory drugs (NSAIDs) block the arachidonic acid pathway and decrease production of prostaglandins and thromboxanes. These can lead to vasoconstriction, dermal ischemia, and further tissue damage.^6,7 No studies have demonstrated that any particular anti-inflammatory agent or dosing is clearly related to outcome, however. One rabbit ear model study showed 23% tissue survival with aspirin versus 0% in the control group.⁷ However, aspirin theoretically blocks production of certain prostaglandins that are beneficial to wound healing.

Hydration Treatment

Vascular stasis can result from frostbite injury, thus appropriate hydration and avoidance of hypovolemia are important for frostbite recovery. Intravenous normal saline should be given to maintain normal urine output. IV fluids should optimally be warmed before infusion and infused in small, rapid boluses, as slow infusion can result in fluid cooling and even freezing as it passes through tubing. Fluid administration should be optimized to prevent dehydration.⁷

Low Molecular Weight Dextran (LMWD) Treatment

Intravenous low molecular weight dextran (LMWD) decreases blood viscosity by preventing red blood cell aggregation and formation of microthrombi and can be given in the field once it has been warmed. In some animal studies, the extent of tissue necrosis was found to be significantly less than in control subjects when LMWD was used, and was more beneficial if given early.⁷ The use of LMWD has not been evaluated in combination with other treatments such as thrombolytics. LMWD should be given if the animal is not being considered for other systemic treatments, such as thrombolytic therapy.⁷