Sedation in Dromedary Camels

While the terms “anesthesia” and “sedation” are often used interchangeably, there are distinct differences between the two. Anesthesia is a pharmacologically-induced reversible state of amnesia, analgesia, loss of responsiveness, and loss of skeletal muscle reflexes. Sedation is a pharmacologically-induced depression of consciousness during which an animal cannot be easily aroused, but may respond following certain types of stimulation.

In the instances in which sedation is employed in favor of anesthesia, the advantages of doing so typically focus on patient safety, and (to a lesser degree) the circumstances at hand during a given chemical immobilization event. The comparative safety of sedation versus general anesthesia in human and animal patients is well-documented. Sedation is associated with decreased risk in many species, thus it is often considered in place of general anesthesia whenever possible.¹ The focus on the use of sedation in exotic animals such as dromedary camels is a result of the perception of greater anesthetic risk in these animals, particularly in those that have undergone the stress of capture.

Other advantages of sedation include general reduction of anxiety and stress, and for more expeditious diagnostic sampling and therapeutics. In some cases, the risk of handling must be weighed against the risk of foregoing diagnostic testing or procedures, or the risk of general anesthesia. For these patients, sedation often provides an attractive alternative.¹

The Dromedary Camel: Background

Camels are ungulates that inhabit the desert areas of western Asia, northern Africa and east Asia. Camels encompass two main species: the dromedary camel (Camelus dromedaries, or the Arabian camel) and the Bactrian camel (Camelus bactrianus). The dromedary camel has a single hump and lives in the warmer areas of western Asia and Arabia; the Bactrian camel has two humps and is native to east Asia.

The dromedary camel has not occurred in the wild for nearly 2,000 years, having been domesticated beginning approximately 3,500 years ago. According to fossil evidence, the ancestors of modern camels evolved in North America during the Palaeogene period and spread to Asia, later becoming extinct in North America.² Camels were used almost exclusively as pack animals on the Silk Road, the network of routes used by traders between Europe and Asia for more than 1,500 years because they could carry more weight than horses or donkeys, needed less water and were able to thrive on tough desert plants.

Dromedary camels are herbivorous, with a diet consisting of foliage, dry grasses and thorny plants that are common in the desert. Their thick, bifurcated upper lips allow them to access and eat things that other desert animals cannot. When foraging, dromedary camels tend to spread out over large areas eat sparingly from numerous plant sources.

The dromedary camel’s hump consists of fat and fibrous tissue (rather than water) that are used for energy storage. These animals are also uniquely adapted to maintain their internal homeostasis and hydration whether water is plentiful or scarce. When water is available, they can drink up to 30 gallons of water in less than 15 minutes.^1-3

Dromedary camels are diurnal and generally timid, although they are quite social among themselves when in groups or herds. In most cases, they can be found in groups of four to six individuals. In family groups, the male is dominant and brings up the family from the rear, with the several females with which he mates taking turns leading the group.

All camel species are polygamous, with a breeding season that spans from November through March. Gestation lasts up to 13 months, with one calf or occasionally twins being born. Calves can usually stand within 8 hours, and remain with the herd until they are old enough to become independent.²

Dromedary camels were first introduced into Australia in the 1840's to assist in the exploration of inland Australia, and as a result, there are over one million feral camels in the rangeland ecosystems of Australia today.⁵ Unfortunately, these animals are causing significant damage to the natural environment. As a control method, radio-collared camels are being used to enhance population control programs. The routinely-performed procedure of radio-collaring includes the chemical immobilization of these animals.

Chemical Immobilization and Risks in Dromedary Camels

Given their level of domestication, dromedary camels are quite tractable, therefore physical restraint and local anesthetic techniques are frequently used to provide immobility and analgesia. General anesthesia techniques are similar to those for ruminants and horses. Regurgitation of compartment one (C1) of the stomach contents (which can occur in many chemically-immobilized ruminants), postoperative nasal congestion and associated respiratory distress postextubation are potential hazards associated with anesthesia in camels.⁷ Observation and monitoring of palpebral and ocular reflexes, eyeball position, and pupil size can be used to monitor the depth of anesthesia. Other risks associated with the capture of dromedary camels include hypothermia, hyperthermia, frostbite, bloat, respiratory depression/arrest and cardiac arrest. Usually however, recovery from anesthesia in dromedary camels is uneventful.^7,10

Disadvantages of sedation (versus anesthesia) can include incomplete elimination of patient movement, patient semi-awareness, and lack of complete analgesia. The most obvious risk in these cases is an increased danger to handlers, since camels are very large animals. These disadvantages can be overcome with careful dosing and monitoring, effective patient handling and efficient use of analgesics when handing and/or when 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 available¹

It should be noted that endotracheal intubation (general anesthesia) is recommended for any camel undergoing procedures longer than 20 minutes.⁷

Agents for the Sedation of Dromedary Camels

In general, sedatives produce calmness, loss of aggression and loss of alertness which are usually required during transportation and for minor procedures. In this condition, a camel is not immobilized fully and can be aroused by various disturbances. Therefore, sedatives 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 synergistic effect of tranquilizers and anesthetics is far greater than the individual effect of either of the two drugs relative to attaining smooth induction, good muscle relaxation and smoother recovery.⁶

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.^6,8

For the purposes of pre-anesthesia and sedation, midazolam is often used in human and veterinary medicine due to its wide margin of safety. When combined with opioids, 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/groups. In all cases, an animal can still react to handling and noxious stimuli to some degree.⁵

When used alone, sedation with midazolam 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.⁹

Drugs used for the sedation of dromedary camels may vary depending upon the preference and experience of the veterinarian or wildlife management personnel. The available literature often 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 animal.^9,10 This is primarily due to the relative safety of modern drug formulations, which allow for much more latitude in dosing without putting an animal’s health or life at risk.