Abstract

Over 50 camels were anesthetized for a variety of reasons including physical examination, suturing, eye enucleation, uterine prolapse and castration. All procedures were undertaken as normal veterinary management of a 250 head Turkana and Somali type camel herd in central Kenya during 1996 and 1997. Xylazine, medetomidine, ketamine and etorphine were compared as anesthetic agents (Table 1). Anesthetic reversals were accomplished with yohimbine, tolazoline, atipamezole and diprenorphine. Initial doses were given using manual restraint or in a camel restraint chute and the animals were released to observe pharmacologic effects. Second doses were administered by hand with manual restraint. Camels can demonstrate a wide range of attitudes from extremely calm to absolutely wild. Anesthetic doses should be interpreted with this fact in mind.

Table 1. Trial of three methods of medetomidine/ketamine/atipamezole administration in camels

Xylazine is a commonly used and effective sedative and anaesthetic agent for camels. A wide dosage range, from 0.25–2.0 mg/kg, is published for immobilization.^1-6,8 My experience with semi calm camels is that 0.25 mg/kg i.v. was insufficient except for very calm or depressed animals (n=2). Dosages of 0.4–0.7 mg/kg i.m. or i.v. were effective to produce sedate animals (n=15) for examination and further pharmacologic manipulation. In some individuals, 0.7 mg/kg i.v. induced recumbency (n=2). Heart rates ranged from 30–66 beats/min and respiratory rates from 4–28 breaths/min.

Ketamine has been reported at doses of 1–2 mg/kg i.v. when given after xylazine to induce recumbency with sufficient anesthesia for minor surgical procedures.^3,5,8 I have found that ketamine dosages as low as 0.6 mg/kg i.v. (range: 0.6–1.0 mg/kg) will induce recumbency when given after xylazine; 2–30 min after i.v. xylazine (n=7) and 15–35 min after intramuscular xylazine (n=6). Caution with xylazine is warranted as incidence of unexplained anesthetic deaths have been reported.²

Reversal of xylazine with yohimbine at 0.4 mg/kg i.v. (n=2) is incomplete with animals remaining ataxic for up to 1 hr after injection, with salivation and drooping lips evident. Reversal with tolazoline i.v. at 1 mg/kg (double a published dose²) allowed for immediate standing (n=10) however half of these animals returned to lateral recumbency multiple times after administration. Tolazoline at 4 mg/kg i.v. (labeled equine dose) allowed sustained standing (n=3) however residual effects of salivation, drooping lips, and soft stool immediately following the procedure.

Etorphine has been reported at 0.0055–0.011 mg/kg up to a 4 mg maximum for anesthesia.^3,5,8 This was attempted in two animals at 0.011 mg/kg combined with 20 mg xylazine and 12 mg acepromazine i.m. Animals became recumbent however demonstrated muscle rigidity, tremors, and severe opisthotonos. Average physiologic parameters were: heart rate, 60 beats/min (range: 48–79); respiratory rate, 26 breaths/min (range: 18–36); and the time to recumbency was 6–7 min. Combined with its inherent danger to humans, etorphine is not an ideal drug for camels.

Medetomidine/ketamine combinations gave remarkably calm inductions and reversal with atipamezole allowed for fast, smooth recoveries in dromedaries (n=20). Three trials were performed: A) medetomidine i.m.+ketamine i.v., B) medetomidine i.v.+ketamine i.v., and C) medetomidine+ketamine given together i.m. to simulate a projectile syringe dosage. When the two drugs were given separately the two injections were 7–32 min apart.

An ideal dose appears to be medetomidine at 0.05 mg/kg either i.v. or i.m. followed by ketamine at 0.6 mg/kg i.v. or i.m. When both drugs were given i.m. the ketamine was increased to 1.0 mg/kg (n=6). Medetomidine doses of less that 0.04 mg/kg were insufficient and required doses of ketamine of over 0.6 mg/kg (n=2). Using more than 0.6 mg/kg ketamine i.v. (n=2) or 1.0 mg/kg i.m. (n=2) increased the incidence of side effects such as apnea, tachycardia and post reversal ataxia especially during short procedures (n=6). Reversal was achieved with 0.15 mg/kg (range: 0.135–0.25) atipamezole i.v. (n=20) and regardless of the route of medetomidine administration, animals stood within 2 min (range: <1–3 min). Atipamezole is also effective when given i.m. (n=2) and for completely reversing the effects of xylazine after the tolazoline failure.

In order to achieve complete analgesia for painful procedures such as castration, local use of lidocaine is recommended. There is an excellent reference on regional and local nerve blocks in camels.⁴ Other anesthetic protocols have been reported using phenothiazines, detomidine, diazepam, chloral hydrate, magnesium sulfate, guaifenesin, barbiturates, and halothane.^3-6,8

Regurgitation is a distinct possibility (n=2) and an enforced fasting time of more than 12 hr will reduce its incidence. Camels are susceptible to ruminal tympany and the other deleterious effects of long term lateral recumbency like other herbivores.

The live weights of these camels ranged from 217–355 kg and were calculated from body measurements. The formula used was: estimated live weight (kg) = shoulder height (m) x thoracic girth (m) x abdominal girth (m) x 50 (or 48 for young animals).⁷ Another method of weight estimation was attempted using a formula designed by the Indian Army Veterinary Corps.⁵ Thoracic girth and length measurement are taken in cm and the weight derived from a chart. To this weight, a “hump factor,” which accounts for the size of the hump, must be added. In this study, the body measurements derived were too large to fit the Indian scheme and this second method is probably more suited to more compact camels than the taller, slender East African varieties.

Appendix: Drugs Used

Atipamezole: Antisedan, 5 mg/ml, Orion Farmos, Espoo, Finland; etorphine: Large Animal Immobilon, 2.45 mg/ml with acepromazine 10 mg/ml, C-Vet Veterinary Products, Leyland, Lanc. PR5 3QN, UK; ketamine: Ketaset, 100 mg/ml, Fort Dodge La Çb., Inc., Fort Dodge, Iowa, USA or ketamine hydrochloride injection 50 mg/ml, Rotexmedica GMBH, Trittau, Germany; medetomidine: Zalopine, 10 mg/ml, Orion Farmos, Espoo, Finland; tolazoline: Tolazine, 100 mg/ml, Lloyd Labs., Shenadoah, IA, USA; xylazine: Rompun, 20 mg/ml, Bayer, Leverkusen, Germany or Xylazine-100 Injectable, 100 mg/ml, The Butler Company, Columbus, OH, USA; and yohimbine: Antagonil, 5 mg/ml, Wildlife Pharmacueticals, Inc., Fort Collins, CO, USA or Yobine Injection, 2 mg/ml, Lloyd Labs., Shenanadoah, IA, USA.

Acknowledgments

We thank the owners, and our co-workers, particularly the camel crew, of Ol Jogi for their support. Many of the procedures were performed with veterinary students from the University of Nairobi.

Literature Cited

1.  Bonath KH. 1995. Xylazine-anaesthesia and antagonism in dromedaries. In: Evans JO, SP Simpkins, DJ Atkins, eds. Camel Keeping in Kenya. Republic of Kenya, Ministry of Agriculture, Livestock Development and Marketing, Nairobi, Kenya. Pp. 7:20–7:21.

2.  Cran HR. 1995. Castration of camels. In: Evans JO, SP Simpkins, DJ Atkins, eds. Camel Keeping in Kenya. Republic of Kenya, Ministry of Agriculture, Livestock Development and Marketing, Nairobi, Kenya. Pp. 7:22–7:23.

3.  Fowler ME. 1992. Anaesthesia and surgery in camels. Proc. 1st int. Camel Conf. 341–6.

4.  Gahlot TK, DS Chouhan. 1992. Camel Surgery. Gyan Prakashan Mandir, Birkaner - 334 003 India.

5.  Higgins AJ, RA Kock. 1986. A guide to the clinical examination, chemical restraint and medication of the camel. In: Higgins AJ, ed. The Camel in Health and Disease. Balliere Tindall, London, Pp. 21–40.

6.  Peshin PK, J Singh, AP Singh, DB Patil. 1992. Experimental and clinical evaluation of some sedatives and anesthetic agents in dromedary camels (Camelus dromedarius). Proc. 1st int. Camel Conf. 371–4.

7.  Simpkin SP. 1995. Data collection and herd monitoring. In: Evans JO, SP Simpkins, DJ Atkins, eds. Camel Keeping in Kenya. Republic of Kenya, Ministry of Agriculture, Livestock Development and Marketing, Nairobi, Kenya. Pp. 8.1–4.

8.  White RJ. 1986. Anaesthetic management of the camel. In: Higgins AJ, ed. The Camel in Health and Disease. Balliere Tindall, London, Pp. 136–148.