“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 contrast, “anesthesia” is a pharmacologically-induced reversible state of amnesia, analgesia, loss of responsiveness and loss of skeletal muscle reflexes. The term “chemical immobilization” covers both sedation and anesthesia; the advantages of sedation over general anesthesia typically focus on patient safety and the circumstances at hand during a chemical immobilization event.
Sedation is associated with decreased risk in many species, thus it is often considered in place of general anesthesia whenever possible.1 The comparative safety of sedation over general anesthesia in human and animal patients is also well-documented. The focus on the use of sedation in exotic animals is a result of the perception of greater anesthetic risk, particularly in those that have undergone the stress of capture.
Other advantages of sedation include 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 risk of general anesthesia. For these patients, sedation provides an attractive alternative.1
The alpaca (Vicugña pacos) is a South American camelid (Camelidae). This group of animals is also referenced as lamoids, a word used for several species of animals including llamas, alpacas, vicuñas, and guanacos. Like camels, lamoids are believed to have originated in North America over 40 million years ago, with lamoids migrating to South America and camels migrating west via the Bering Strait and later becoming extinct in North America.2
Alpacas are the most limited in range and the most specialized of the four species of lamoids, being adapted to altitudes from 13,000 to 15,500 feet.3 They are slender-bodied animals with a long neck and long legs, a short tail, a small head, and large, tapering ears. Distinguished from llamas by their smaller size, alpaca are the smallest of the domesticated lamoids. The weight of an adult alpaca ranges from 120 to 140 lbs, with a height ranging from 2 to 3 feet.1
The disposition of alpacas is generally friendly and gentle. In the Andes, the mating period for alpacas runs from August through September. Their babies are called crias, which typically weigh 15-20 pounds at birth. Adult alpaca reach about 3 feet in height and 150 pounds in weight.3 Alpacas typically live from 15 to 25 years.
Lamoids have been developed (bred) over many thousands of years, thus they vary by size and purpose. Some, such as llamas, have been bred for use as pack animals, while others (such as alpacas) were bred for their fleece.2 The alpaca encompasses two breed types: the huacaya and the suri. Huacayas are the more common type of alpaca, and account for about 90% of all alpacas.2 The two breed types differ mostly in terms of the properties of their fleece.
Alpacas are the most widely-used lamoids for fleece production. Their fleece is lightweight, strong, high in insulation value and very resistant to moisture. It has been reported that during the height of the Incan civilization, the wearing of robes made of alpaca fleece was reserved for the nobility.4 Alpaca wool fibers are hollow, which gives them the ability to insulate very well and to absorb moisture. As a result, alpaca farming has become a worldwide industry.
Alpacas are pseudo-ruminants, possessing a single stomach divided into three compartments (instead of four, like other ruminants). In the field, alpacas graze on grasses and plants. On farms, alpacas will eat grass or hay. They consume approximately two pounds per 125 pounds of body weight daily in hay or fresh pasture. Some farmers supplement extra alfalfa to alpacas that are leaner, or those which live in very cold temperatures.4
There are many physiological and metabolic changes that occur 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.
Given their level of domestication, camelids tend to be easy to handle, thus 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 the chemical immobilization of alpacas.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 alpacas include hypothermia, hyperthermia, frostbite, bloat, respiratory depression/arrest and cardiac arrest. Usually however, recovery from anesthesia in alpacas is uneventful.6,9
Disadvantages of sedation versus anesthesia in alpaca 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. 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.5
The American College of Veterinary Anesthetists (ACVA) has published recommendations for monitoring animals that are sedated without general anesthesia (ACVA recommendations):
Sedatives produce calmness, loss of aggression and loss of alertness, which are usually required during transportation and for minor procedures. In this condition, an alpaca is not immobilized fully and can be aroused by various disturbances. Thus, 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 combined synergistic effect of tranquilizers and anesthetics is far greater than the individual effect of either of the two drugs in attaining smooth induction, good muscle relaxation and smoother recovery.6
Sedatives typically used in veterinary medicine include drugs such as acepromazine, midazolam, alprazolam, amitriptyline, buspirone, clomipramine, dexmedetomidine, diazepam, fluoxetine, lorazepam, paroxetine, sertraline, or trazodone. 6,8 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.5 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, patients still react somewhat to handling and noxious stimuli.6
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.9
The drugs used for sedating alpaca often vary depending upon the preference and experience of the veterinarian or wildlife management personnel. The 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.8,9 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.
1Lennox, A., DVM. Sedation as an Alternative to General Anesthesia in Exotic Patients. Delaware Valley Academy Veterinary News, March, 2010.