Chinese Water Deer Sedation

Deer are among the most well-recognized wild animals around the world. One of the more unusual deer species with regard to appearance is the Chinese water deer (Hydropotes inermis). In its natural range, this small deer inhabits the river valleys of eastern China and Korea. Chinese water deer were initially introduced to zoos in England in the late 1800s. Some were deliberately released into surrounding woodlands in the early 1900s, and there have subsequently been numerous releases, translocations, and escapes of these deer in the UK.¹ Since then, Chinese water deer have also been introduced to many other countries, including the United States.

Chinese water deer are a medium-brown color and lack the white rump seen in other species of deer. This species is the only deer in which the males have no antlers. Instead, they carry tusk-like upper canines which resemble fangs. Slightly smaller than a roe deer, the Chinese water deer’s large, fluffy ears, black eyes and small black nose are said to give them a teddy bear-like appearance. They favor wet, marshy habitat and are strong swimmers.

Adult male Chinese water deer stand about 20 inches tall at the shoulder and weigh up to 30 pounds, while females weigh up to 25 pounds. The lifespan of the Chinese water deer is 10 to 12 years.² The hind legs of the Chinese water deer are powerful and longer than the front legs, which gives them a rabbit-like appearance when running.¹

Chinese water deer prefer wetlands adjoining woodlands, although they will occasionally range onto nearby farmland. They typically feed on weeds, grasses, herbs and some browse, usually around dawn and dusk. Water deer do not form herds, but are seen either solitarily or in family groups of a doe with her fawns. Groups sometimes come together at choice feeding areas.²

During the December rut for Chinese water deer, males fight for females with their tusks. Females often give birth to 2 to 4 offspring (although up to 8 and more have been reported) after a gestation of 160- 210 days. Fawns are born from May to June. Although they are usually weaned after 3 months, fawns often remain with their mother into winter before striking out on their own in the spring.^1,2

Anesthesia vs. Sedation in Chinese Water Deer

The sedation of Chinese water deer is sometimes required for the purposes of research, wildlife management and medical care. First, it is necessary to distinguish between sedation and anesthesia. While “sedation” and “anesthesia” are often used interchangeably, these are two separate modalities of chemical immobilization. Anesthesia is a pharmacologically-induced reversible state of amnesia, analgesia, loss of responsiveness, and loss of skeletal muscle reflexes, whereas sedation is a pharmacologically-induced depression of consciousness during which an animal cannot be easily aroused, but may respond following repeated or painful stimulation.

The relative safety of sedation over general anesthesia has been well-established in both animal and human patients, therefore, sedation is often considered in place of general anesthesia whenever possible.³ Until the advent of potent opiates, some deer species were known to be very difficult to safely capture or immobilize chemically.⁴ The focus on the use of sedation in exotic animals such as deer is a direct result of the perception of greater anesthetic risk in these patients, especially in those that are ill or debilitated.

Other advantages of sedation include a general reduction of anxiety and stress related to disease processes such as respiratory disease, and for diagnostic sampling and therapeutics. In some cases, the risk of handling must be weighed against the risk of foregoing diagnostic testing or procedures, or risk of general anesthesia.³

Chemical Immobilization and Risks

A variety of physiological and metabolic changes occur in a deer’s body as a result of chemical immobilization, not all of which are caused by the immobilizing agents. Many of these changes are due to the capture of the animal itself, the most serious of which can bring about a condition called capture myopathy. This is believed to be related to a metabolic acidosis caused by extreme exertion over a short period of time, resulting in necrosis of the large muscle masses of the legs and other areas. It leads to the collapse of the animal and eventual death from acidosis, predation or other factors.³Since all deer are prey animals and have evolved with instincts and behaviors gauged to help them survive, this is an inherent risk in deer capture events of any kind.

Other risks associated with the chemical immobilization of Chinese water deer include vomiting and aspiration, hypothermia, hyperthermia, frostbite, bloat, respiratory depression/arrest and cardiac arrest. Each species of deer has its own anesthesia recommendations with intra-species variations of dosages because of diverse individual responses to anesthetic agents.^3,4

Some disadvantages of sedation include incomplete elimination of patient movement, patient semi-awareness, and lack of complete analgesia. So, while drugs and lower dosages used for sedation are linked with greater patient safety, they are not entirely without risk. These disadvantages can be overcome with careful dosing and monitoring, effective patient handling and efficient use of analgesics when handing or procedures are expected to produce discomfort.³

The American College of Veterinary Anesthetists (ACVA) has published recommendations for monitoring animals that are sedated without general anesthesia (ACVA recommendations):

• Palpation of pulse rate, rhythm and quality
• Observation of mucous membrane color and CRT
• Observation of respiratory rate and pattern
• Auscultation
• Pulse oximetry supplemental oxygen, and endotracheal tube (where applicable) and materials to obtain vascular access should be readily available³

Agents for the Sedation of Chinese Water Deer

Sedative drugs produce calmness, loss of aggression and loss of alertness which are generally required during transportation. Animals are not immobilized fully and can be aroused by various disturbances. Therefore, these drugs are usually used singly for only very minor procedures, or as adjuncts to dissociative anesthetics for hastening smoother induction and to reduce the quantity of anesthetic for achieving more effective immobilization. The combined synergistic effect of tranquilizers and anesthetics is far greater than the individual effect of either of the two drugs with respect to smooth induction, good muscle relaxation and smoother recovery.³

Sedatives commonly used in veterinary medicine include drugs such as midazolam, alprazolam, amitriptyline, buspirone, clomipramine, dexmedetomidine, diazepam, fluoxetine, lorazepam, paroxetine, sertraline, or trazodone. Acepromazine is also widely used in veterinary medicine as a sedative. It is a member of the phenothiazine class of sedatives and works primarily by blocking dopamine receptors within the brain, thereby depressing certain brain functions.³

Midazolam is often used in human and veterinary medicine for the purposes of pre-anesthesia and sedation and has a wide margin of safety in many species. When combined with an opioid, its effects are synergistic, allowing a reduction of the amount of either drug.⁴ Dosages most commonly used are 0.5-10 mg/kg, combined with an opioid (butorphanol, buprenorphine, hydromorphone, other). Effects are variable, from slight decrease in activity to lateral recumbency. These effects are likely related to species variability in response and the varying dose rates suggested for different species. In all cases, patients still react somewhat to handling and certain stimuli.¹

When midazolam is used alone, sedation may be adequate in ruminants, camelids and several other species. When used in combination with other drugs (e.g., opioids, ketamine, acepromazine, dexmedetomidine), midazolam provides more reliable sedation. It should be noted that use of sedation and manual restraint alone is inappropriate for any procedure expected to produce discomfort. In mammals, additional sedation can be provided with sub-anesthetic dosages of ketamine, 2-7 mg/kg, or alfaxalone, 1 mg/kg IM. If additional immobilization is essential, low concentrations of inhalant gas can be considered.¹

The drugs used for sedating Chinese water deer may vary depending upon the preference and experience of the veterinarian or wildlife management personnel. The literature suggests that dosing higher when in doubt is in fact safer than dosing conservatively, in that there is more risk to a partially-immobilized animal and to human handlers than there is to a heavily-dosed deer.^4,5 This is due to the increased safety of modern drug formulations, which allow for much more latitude in dosing without putting the animal’s health or life at risk.