Cardiac Arrest in Kudu Antelope During Capture and Chemical Immobilization

Kudu are comprised of two species of spiral-horned antelopes The larger greater kudu (Tragelaphus strepsiceros) is second in size to the largest African antelope, the eland. Males have a beard and have the longest horns of any antelope, at 47–71 inches. They stand 51–59 inches and are narrow-bodied. The smaller lesser kudu (Tragelaphus imberbis) is found in the arid lowland thornbush of northeast and East Africa. They stand at around 39 inches high and weigh 202–238 pounds. The lesser kudu has a dark coat with 12–15 vertical white stripes, a broad chest with throat patches, a nose chevron and cheek patches.1 In both species, the males have corkscrew horns.

The veterinary care of kudu has become a routine occurrence due to the integration of veterinary medicine in wildlife management programs, zoological collections, exotic animal ranching expansions and the private collection of wildlife species.² As a result, wildlife managers and veterinarians are frequently called upon to anesthetize and handle these animals.

According to the available literature, each species of antelope has its own anesthesia recommendation with intra-species variations of dosages because of diverse individual responses to anesthetic agents.^3,4 These variations often present an increased risk of complications during anesthetic events. It has been widely reported that until the advent of potent opiates, certain species of antelope were very difficult to safely capture or anesthetize.³

Risks for Cardiac Arrest in Kudu During Capture

Capture and/or chemical immobilization can result in cardiac arrest, or cardiopulmonary arrest (CPA) events in antelope, particularly under field conditions. In some instances, the stress of capture (depending upon the method of capture) can significantly increase the likelihood of cardiac arrest in these animals.

CPA is characterized by an abrupt, complete failure of the respiratory and circulatory systems. The subsequent lack of oxygen transport can quickly cause systemic cellular death from oxygen depletion.³ If left untreated, cerebral hypoxia can result in death within four to six minutes of a CPA event.⁴ In these cases, prompt cardiopulmonary resuscitation is imperative.

While under anesthesia, common causes of CPA can include vagal stimulation, unstable cardiac arrhythmias, severe electrolyte disturbances, exacerbated cardiorespiratory disorders (e.g., congestive heart failure, hypoxia)² or a variety of comorbidities. 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 and fixed, dilated pupils.

Responding to Cardiac Arrest in Kudu

Monitoring core body temperature is essential in antelope anesthesia,^3,4 and intubation has been widely recommended for any anesthetized antelope that needs to be transported or anesthetized for greater than one hour. Until the more recent use of formulated drugs (e.g., combinations of α2-agonists such as medetomidine, detomidine, xylazine and their reversal agents), opioids were the mainstay of antelope anesthesia in wildlife and captive care.³

Adopted from human emergency medicine, cardiopulmonary cerebral resuscitation in antelope involves three stages: basic life support (BLS), advanced life support (ALS), and post resuscitation care.³ The first stage involves establishing an open and clear airway, providing assisted ventilation, and performing chest compressions. If an antelope’s pulse becomes absent or weak, all administration of immobilizing drugs must be suspended and external cardiac massage should be initiated. Veterinary patients can usually be easily and safely ventilated with a bag-valve mask,¹ the caveat being that this may not be available under field conditions.

Venous access can be established by 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.¹ Epinephrine at 0.2 mg/kg (concentrated at 1/10,000) should be given IV or intracardially (IC) while cardiac massage continues. If the animal 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.⁴

Antelope that are restored to a perfusing cardiac rhythm can experience rearrest, especially if the original cause of the CPA event has not been identified. Therefore, resuscitated kudu 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.¹