Antelope Dehydration During Capture and Chemical Immobilization
Field immobilization of antelope is sometimes required for medical examination, blood sample collection, and animal identification, and the importance of performing such procedures for research and conservation projects is widely acknowledged.1 As these activities continue to become more common, the need to assess their negative effects increases in order to ensure ethical standards and the validity of research results. Research in this area itself has revealed that the physiological and behavioral effects of capture are as important as the direct risks of injury or death of an animal.2
There are a number of common stressors attendant to the chemical immobilization of antelope that can, in some cases, lead to complications during or after an anesthetic event. The overall health of an individual animal (which might be poor, and in some cases the very reason for its capture) is also a factor affecting the potential for complications during and after anesthesia.
In general, these stressors—stimuli or agents inducing stress—fall into four categories:
- Physiological: Heavy exercise, hemorrhage, hyperthermia, shock, pain, infection
- Physical: Trauma/surgery, intense heat/cold
- Chemical: Hypoxemia, acid-base imbalance, anesthetic drugs
- Emotional: Anxiety, fear3
Obviously, chemical immobilization agents are represented by the third category, although elements of the other three are often included in immobilization events. The physical stress of capture and/or attempts to escape during capture on the part of an animal certainly constitute physiological stress; surgical and even environmental conditions can bring about physical stress, and anxiety and fear are nearly always a component to some degree in a capture scenario.
The effects of acute stress during capture can include spikes in adrenaline, cortisol levels, heart rate, blood pressure, respiration, metabolic rate, blood glucose, lactic acid and body temperature, while bringing about a decrease in pH and a redistribution of blood within the organs. The effects of capture and anesthesia can activate the fight-or-flight response, HPA-axis activation, hyperthermia, respiratory depression (hypoxemia), lactid acid build-up, acidosis; in severe cases, this can lead to neurological/myocardial dysfunction, multi-organ failure, capture myopathy and death.4
Dehydration in Antelope
Antelope constitute a wide assortment of ruminants with worldwide distribution. Antelope is a common name given to various members of the family Antilocapridae and Bovidae. The pronghorn antelope, Antilocapra americana, is the only member in the family Antilocapridae, which has lead to some controversy in zoological circles as to whether or not it is a true antelope. Antelope males and some females of certain species have unbranched horns attached to the frontal bones of the skull.
On its face, dehydration may seem like a minor concern compared to some surgical complications, but inasmuch as it can lead directly to cardiac arrest, dehydration (a reduction of the body’s water content) is potentially quite dangerous. All animals require water to ensure their bodies are working properly. It is so important that essentially all bodily functions require it to remain operative. If an animal loses more water and electrolytes than it is taking in, it will begin to dehydrate and its health will quickly deteriorate.
Electrolytes are minerals that naturally occur in all animals, and they are essential for proper health. Electrolytes are comprised of sodium, chloride, and potassium, and facilitate the movement of nutrients into cells, aid in muscle function, and help regulate nerve activities.3,4 An animal’s natural activities—breathing, urinating, and defecating, as well as simple evaporation—can all cause it to lose fluids. When an animal eats and drinks, the lost water and electrolytes are replaced. If the animal’s fluid intake becomes less than what they are losing, dehydration will occur. This causes a reduction in bodily fluids that reduces blood flow and the delivery of oxygen to organs and tissues.
Understanding Dehydration in Antelope
To understand dehydration, one must first understand the distribution of fluid and water in the body. Total body water (TBW) comprises approximately 60% of an animal’s body weight. Approximately 67% of TBW is found inside the body’s cells; this is referred to as intracellular fluid (ICF). The remaining 33% of TBW is the extracellular fluid (ECF), which comprises:
- Interstitial fluid, which bathes cells and tissues (~24% of TBW)
- Plasma, the liquid portion of blood, which constitutes most of intravascular volume (~8%–10% of TBW)
- Transcellular fluid, which comprises synovial joint fluid, cerebrospinal fluid, bile, and the fluid in the linings of the peritoneal cavity, pericardium, and pleural space (~2% of TBW)2
A simple approximate formula for the distribution of fluids in the body is the 60:40:20 rule: 60% of an animal’s body weight is water, 40% of body weight is ICF, and 20% of body weight is ECF.2,3
Dehydration can be caused by hyperthermia, chronic vomiting or diarrhea, excessive urination or wound drainage. Due to the stressful nature of capture and chemical immobilization events, they have been known to bring about dehydration. In both human and veterinary practices, IV fluids are usually administered prophylactically, depending on the nature of the procedure. Veterinarians often provide fluid therapy to patients for many reasons, including correction of dehydration, expansion and support of intravascular volume, correction of electrolyte disturbances, and encouragement of appropriate redistribution of fluids that may be in the wrong compartment (e.g., peritoneal effusion).2
The available literature states that each species of antelope has its own anesthesia recommendation with intra-species variations of dosages because of diverse individual responses to anesthetic agents.2,3 These variations are of course factors in the risk of dehydration in these species, and attendant factors (e.g., stress, venue, individual animal and field conditions) must also be taken into account. Prior to the advent of some of the newer drug formulations, species such as the pronghorn were known to be notoriously difficult to immobilize successfully.
Treating Dehydration in Antelope
Monitoring core body temperature is essential in antelope anesthesia.3 Hyperthermia and subsequent capture myopathy is a commonly-encountered problem with antelope anesthesia. Intubation has been widely recommended for any anesthetized antelope that needs to be transported or anesthetized for greater than one hour.
During anesthetic/immobilization events, hydration status can be assessed using various tests. One of the easiest to perform is a skin tent test to check the turgor (moisture level) of the skin. To do this, the skin over the thorax or lumbar region is pulled away from the back. In a well-hydrated animal, the skin immediately returns to its normal resting position. If the tent formed remains standing, it is a likely indication of dehydration. If there is evidence of dehydration in an antelope during a procedure, all administration of immobilizing drugs must be immediately suspended. Fluid therapy should begin in the form of lactated Ringer’s solution or 0.9% saline, IV, SQ or IP.3
Perioperative IV fluid therapy is very common in veterinary medicine and allows practitioners to restore intravascular volume, correct dehydration, and administer IV medications quickly.4 While perioperative fluid therapy under many field conditions may be impractical, fluids should always be available in the case of dehydration when chemically immobilizing antelope.
1Laricchiuta P, De Monte V, Campolo M, Grano F, Iarussi F, Crovace A, Staffieri F. Evaluation of a butorphanol, detomidine, and midazolam combination for immobilization of captive Nile lechwe antelopes (Kobus magaceros). J Wildl Dis. 2012 Jul;48(3):739-46.
2Brivio F, Grignolio S, Sica N, Cerise S, Bassano B (2015) Assessing the Impact of Capture on Wild Animals: The Case Study of Chemical Immobilisation on Alpine Ibex. PLoS ONE 10(6): e0130957.
3Kreeger T., Arnemo, J., Raath, J. Handbook of Wildlife Chemical Immobilization, International Edition, Wildlife Pharmaceuticals, Inc., Fort Collins, CO. (2002).
4Ball, L. Antelope Anesthesia. Wiley Online Library, 25 July 2014,
About NexGen Pharmaceuticals
NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.
Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.
Disclaimer
The information contained in this blog post is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the medications shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular medication. You should consult your veterinarian about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the medications to diagnose, cure or prevent disease. Medications compounded by NexGen Pharmaceuticals are prepared at the direction of a veterinarian. NexGen Pharmaceuticals compounded veterinary preparations are not intended for use in food and food-producing animals.
NexGen Pharmaceuticals, LLC does not recommend, endorse or make any representation about the efficacy, appropriateness or suitability of any specific dosing, products, procedures, treatments, services, opinions, veterinary care providers or other information that may be contained in this blog post. NEXGEN PHARMACEUTICALS, LLC IS NOT RESPONSIBLE NOR LIABLE FOR ANY ADVICE, COURSE OF TREATMENT, DIAGNOSIS OR ANY OTHER INFORMATION, SERVICES OR PRODUCTS THAT YOU OBTAIN THROUGH THIS BLOG POST.