Cardiac Arrest in Llamas During Capture and Chemical Immobilization

The llama (Lama glama) is a domesticated member of the camel family (Camelidae). This group of animals, whose native range is the South American Andes, are also known as lamoids or New World camelids. Like camels, lamoids originated in North America over 40 million years ago, with lamoids migrating to South America and camels migrating west via the Bering Strait, later becoming extinct in North America.^1,2 Unlike camels, llamas and other lamoids do not have the iconic back humps that make camels so easily recognizable.

Llamas and other lamoids have been so widely domesticated over the last several thousand years that there are few occurring in the wild. Today, domesticated llama herds are found in the Andean highlands of the western South American continent. They are also farmed, primarily for their fleece, in a number of other countries around the world.^2,3

The largest of the New World camelids, llamas are slender-bodied animals with long legs, long necks, short tails and large ears. They average 45 inches in height at the shoulder; adult males weigh between 300 and 400 pounds, and adult females weigh between 230 and 350 pounds.³ While most llamas are white in color, they may also be solid black or brown, or white with brown or black markings.

Llamas are very efficient pack animals, and have long been used by the Andean people to carry goods and supplies through difficult mountain regions. A 250 pound llama is able to carry a load of 100 to 130 pounds for around 15 to 20 miles a day. When a llama is burdened with too much weight however, it will sit down and refuse to move until their load is reduced. Llamas are also used for food, wool, hides, tallow for candles, and dried dung for fuel.²

Llamas are grazing animals; in their native range, they feed mostly on grass. Like cows, llamas regurgitate their food and chew it as cud. Unlike cows however, they are pseudo ruminants with a three-chambered stomach (unlike true ruminants such as cows, which have four-chambered stomachs). Llamas can also survive on other plants, and require little water. Llamas breed in the late summer and fall. Their gestation period is approximately 11 months, after which the female gives birth to one young.³

Llamas and Chemical Immobilization

Wildlife management personnel, biologists, veterinarians in zoos and llama farmers are regularly called upon to chemically immobilize llamas for medical treatment and other purposes. Unfortunately, such procedures carry the risk for a variety of complications in these animals. These include, but are not limited to vomiting and aspiration, respiratory depression, respiratory arrest, bloat, capture myopathy and cardiac arrest.

Varied species protocols and dosage variations for immobilizing drugs present an increased risk of complications during anesthetic events. Until the advent of formulated drugs (e.g., combinations of α2-agonists such as medetomidine, detomidine, xylazine and their reversal agents), opioids were the mainstay of llama anesthesia in wildlife and captive care, and are still widely utilized.⁵ Opioids are still widely used, singly and in combination, for the chemical immobilization of wild species. However, they have the potential to cause cardiopulmonary distress, which should be noted when these drugs are used.

Xylazine is often used to provide sedation or, in higher doses, restraint for llamas. Xylazine can be used for sedation without recumbency. Higher dosages will result in recumbency and provide a light plane of anesthesia for 20–30 min. Simultaneous administration of xylazine, ketamine, and butorphanol usually provides 20–30 min of recumbent restraint.

Tolazoline has activity at both alpha-1and alpha-2 receptors. Although doxapram, an analeptic, will reverse xylazine sedation in cattle and dogs, it will not reverse xylazine sedation in camelids, even when given in doses as high as 2.0 mg/kgIV. Tolazoline can cause vasodilatation because of its alpha-1effect. Caution should therefore be exercised when tolazoline is given to animals with compromised cardiovascular status to avoid precipitating shock. Monitoring core body temperature is essential in llama anesthesia,^5,6 and it is recommended that llamas be orotracheally-intubated for procedures lasting more than 20 minutes.⁶

Cardiac Arrest as a Complication in Llamas

Cardiac arrest (also known as cardiopulmonary arrest or CPA) is an abrupt and complete failure of the respiratory and circulatory systems. The resulting lack of oxygen transport can quickly cause cellular death from oxygen depletion.⁵ If left untreated, cerebral hypoxia can result in death within four to six minutes of a CPA event.^6,7 In these cases, prompt cardiopulmonary resuscitation is imperative.

Despite their tractability and level of domestication, capture and/or chemical immobilization can result in CPA events in llamas. In some instances, the stress of capture (depending upon the method 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 or exacerbated cardiorespiratory disorders (e.g., congestive heart failure, hypoxia).⁵

Clinical signs of an impending CPA event can include:

• Dramatic changes in breathing effort, rate, or rhythm
• Significant hypotension
• Absence of a pulse
• Irregular or inaudible heart sounds
• Changes in the heart rate or rhythm
• Changes in mucous membrane color
• Fixed, dilated pupils

Responding to Cardiac Arrest in Llamas

Cardiopulmonary resuscitation in llamas involves three stages:

• Basic life support (BLS),
• Advanced life support (ALS)
• Post resuscitation care

Establishing an open and clear airway, providing assisted ventilation, and performing chest compressions are included in the first stage. If the llama’s pulse becomes absent or weak, all administration of immobilizing drugs must be ceased and external cardiac massage initiated. The llama can usually be easily ventilated with a bag-valve mask,^5,7 although these are often unavailable under field conditions.

Venous access can be established 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.⁵ Epinephrine at 0.2 mg/kg (concentrated at 1/10,000) should be given IV or intracardially (IC) while cardiac massage continues. If the llama 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.⁶

Llamas that are restored to a perfusing cardiac rhythm may experience rearrest. Therefore, resuscitated animals usually 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