Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
DRUGS AND ANESTHESIA How to Anesthetize Donkeys for Surgical Procedures in the Field Lori A. Bidwell, DVM, Diplomate ACVA Author’s address: Ross University School of Veterinary Medicine, PO Box 334, St. Kitts, West Indies; e-mail: [email protected]. © 2010 AAEP. 1. Introduction Donkeys are an important part of the work force in much of the world. Practitioners working with donkeys in the United States and those participating in equitarian initiatives abroad should understand the difference between donkeys and horses in relation to anesthesia. Although it is tempting to treat a donkey like a horse, there are important differences in relation to handling and drug doses. Additionally, it is important to understand alternative anesthetic protocols because a practitioner may be limited to minimal or alternative drugs when working in a developing country. 2. Behavior and Physiology A tame donkey can be easy to handle but a feral or minimally handled donkey can be frustrating. Donkeys are intelligent and typically take little time and handling to tame and train. They tend to lean into pressure and lean against a pulling force; therefore, the best technique for moving a donkey is gentle coercion. Anatomic and physiologic differences make intravenous injection, orotracheal intubation, and drug dosing more complicated. The cutaneous colli muscle extends over the jugular furrow and can hinder visibility when distending the vein, complicating venepuncture or catheter placement. Plac- NOTES 38 2010 Ⲑ Vol. 56 Ⲑ AAEP PROCEEDINGS ing a local block where a catheter will be placed and making a small skin incision with a surgical blade before placing an intravenous catheter is recommended. Intubation is more difficult because of caudal angulation of the larynx, a pharyngeal diverticulum, excess pharyngeal mucosa, and long paired laryngeal saccules. Additionally, nasal intubation is complicated by narrow nasal passages.1 Drug metabolism is elevated in donkeys compared with horses, resulting in the use of higher doses and more frequent dosing intervals.2– 6 The only known exception to this is the administration of guaifenesin, which seems to require lower dosing because respiratory arrest is easy to achieve when using doses appropriate for a horse.7 3. Sedation and Analgesia Xylazine,a romifidine,b detomidine,c and dexmedetomidined have been safely administered to donkeys using doses similar to those administered to horses with sedation and analgesia of duration shorter than or similar to that in horses. Personality and demeanor should dictate which part of the dose range you select when determining a protocol (Table 1). If intramuscular dosing is required, it is recommended to double the intravenous dose for a similar effect. In a calm, tame donkey, xylazine can be DRUGS AND ANESTHESIA Table 1. Recommended Drug Doses for Sedation, Induction, Maintenance, and Analgesia of Donkeys Dose Sedation Xylazine Romifidine Route of Administration Expected Duration 0.8 mg/kg (0.3–1.0 mg/kg) 0.08 mg/kg (0.05–0.1 mg/kg) IV, IM IV, IM Detomidine 0.01 mg/kg (0.005–0.04 mg/kg) IV, IM, sublingual Dexmedetomidine 0.005 mg/kg (0.0025–0.01 mg/kg) IV, IM 0.03 mg/kg (0.02–0.05 mg/kg) IV, IM, sublingual 15–20 min 30 min to 2 h (duration is dose dependent) 20–40 min (duration is dose dependent) 20–30 min (duration is dose dependent) 30 min to 2 h 2.5 mg/kg 0.05 mg/kg (0.02–0.08 mg/kg) 2.0 mg/kg 2.0 mg/kg 8.0 mg/kg 1.0 mg/kg IV IV IV IV IV IV 10–15 min 10–15 min 10–15 min 10–15 min 20 min 20 min 12.5 g guaifenesin 500 mg ketamine 150 mg xylazine (combined in a 500-ml bag of LRS or 0.9% NaCl) IV (requires an IV catheter) Administering a bolus often results in apnea. Infusion lasts ⬃45 min 0.03 mg/kg (0.02–0.05 mg/kg) 0.006 mg/kg 0.01 mg/kg IV, IM IV, IM, sublingual IV, IM 30–50 min 6h 2–3 h Acepromazine Induction Ketamine Diazepam/midazolam Propofol Alfaxalone Thiopental Telazol Maintenance Triple drip Analgesics Butorphanol Buprenorphine Morphine dosed at 0.8 mg/kg (range, 0.3–1 mg/kg) IV or romifidine administered at 0.08 mg/kg (range, 0.05– 0.1 mg/kg) IV. Detomidine can be given at 0.01 mg/kg (range, 0.005– 0.04 mg/kg) IV, and dexmedetomidine can be dosed at 5 g/kg (range, 2.5–10 g/kg) IV, with sedation lasting 20 –30 min. Acepromazinee can be administered with an ␣-2 agonist if the donkey is agitated or anxious at 0.03 mg/kg (range, 0.02– 0.05 mg/kg) IV or IM. Adding butorphanolf to an ␣-2 agonist produces superior sedation and analgesia at a dose of 0.03 mg/kg (range, 0.02– 0.05 mg/ kg) IV or IM. Buprenorphineg can be administered at 0.006 mg/kg IV, IM, or sublingual. This drug does not produce sedation when given alone and can result in excitement if given to a donkey without an ␣-2 agonist. From observation, the analgesia associated with buprenorphine lasts ⬃6 h. Morphineh can also be administered to donkeys at 0.01 mg/kg IV or IM, and the analgesic effect lasts ⬃2– 4 h. The administration of non-steroidal anti-inflammatory drugs like flunixin megluminei and phenylbutazonej are effective for post-operative pain, although studies have found that metabolism is faster in donkeys than horses, and therefore, dosing intervals should be increased to three times a day rather than twice a day.3,5,6,8 Local anesthetics have similar application and duration in donkeys as those used in horses. should be administered at 2.5 mg/kg and is more effective when combined with diazepaml or midazolamm at 0.05 mg/kg (range, 0.02– 0.08 mg/kg) IV. Propofoln produces smooth induction and recovery with anesthesia that lasts ⬃10 –15 min when administered at 2.0 mg/kg IV. Thiopentalo administered at 8.0 mg/kg IV produces anesthesia that lasts ⬃20 min with slow recovery. Alfaxalone,p a drug that is currently not approved for use in the United States but is approved in Europe and Australia, can be administered at 2.0 mg/kg IV, with anesthesia lasting 10 –15 min. From experience, recovery from alfaxalone in donkeys is slow, with muscle fasciculations and weakness. Miniature donkeys are similar to standard donkeys, although telazolq (the combination of tiletamine and zolazepam) has been used with success and is recommended for induction at 1.0 mg/kg IV.9 The duration of anesthesia using any of these anesthetic protocols can be extended by 3–5 min with an additional IV bolus of the induction agent at one third the initial dose. It is important to protect the donkey’s eyes while anesthetized. Most induction techniques maintain a blink reflex, but it is not always adequate to prevent ulceration of the cornea. Sterile ophthalmic lubricant should be applied to the eyes and a towel should be placed under the down eye to prevent contamination with grass, soil, or shavings. 4. 5. Induction Induction agents that are used in horses can be used in donkeys at similar doses. Dosing of ketaminek Maintenance The combination of guaifenesin,r ketamine, and xylazine, known as “triple drip,” can be used as mainAAEP PROCEEDINGS Ⲑ Vol. 56 Ⲑ 2010 39 DRUGS AND ANESTHESIA tenance anesthesia for donkeys. Because of sensitivity to guaifenesin, a solution of 12.5 g guaifenesin, 500 mg ketamine, and 250 mg xylazine in a 500-ml bag of saline or lactated Ringer’s solution (LRS) is recommended. This combination can be administered after induction at 1 drop/s initially and then given to effect as depth of anesthesia changes. This combination will last for a minor surgical procedure that takes ⬃45 min. A fast bolus of this combination will result in apnea, and therefore, caution should be used during administration. If a portable foal or small animal anesthetic machine is available, miniature and standard donkeys can be intubated and maintained on isofluranes or sevofluranet using anesthetic concentrations similar to horses. Intubation is more complicated than in horses but can be achieved by extending the head in a straight line along the dorsal surface of the donkey. A biteblock (typically PCV piping) can be placed between the incisors, with the endotracheal tube placed through the block to the point of resistance at the larynx. Advancing the tube with gentle manipulation during inhalation will often result in intubation. If there is resistance, retract the tube to the oral cavity, rotate 180°, and try again. 6. Recovery Donkeys typically recover from anesthesia in a calm manner, rolling into sternal until they are alert and capable of standing on the first attempt. Most donkeys will recover unassisted without complication, but they can be assisted in recovery if necessary. Because of small size, they are relatively easy to restrain in a lateral position by placing a knee or both knees on the dorsal neck and pulling their head toward you to prevent the momentum needed to stand. Grabbing the tail for assistance and giving it a boost when they do attempt to stand is tolerated and effective as they tend to stand front end first. 7. Results These techniques have been used with success in ⬃500 anesthetic cases per year run by veterinary students in a university setting. All protocols and procedures were approved by an Institutional Animal Care and Use Committee. 8. Discussion Donkeys can be easy to work with if you understand their personality traits and recognize that they are not horses in their responses to handling and drug metabolism. Pre-medication dosed appropriate for temperament will result in sedation for standing procedures and induction of anesthesia. Induction produces anesthesia lasting between 10 and 20 min with a variety of anesthetic agents used for horses or agents commonly used for small animal patients. The combination of guaifenesin, ketamine, and xylazine or inhalant anesthetic can be used to main40 2010 Ⲑ Vol. 56 Ⲑ AAEP PROCEEDINGS tain anesthesia for longer procedures. Recovery is typically smooth and without complications, but simple assistance can prevent premature attempts at recovery. As more equine practitioners are working abroad in equitarian programs or at home on client donkeys, it is important that they are comfortable anesthetizing these patients. References and Footnotes 1. Lindsay FE, Clayton HM. An anatomical and endoscopic study of the nasopharynx and larynx of the donkey (Equus asinus). J Anat 1986;144:123–132. 2. Peck K, Matthews N, Taylor T, et al. Pharmacokinetics of sulfamethoxazole and trimethoprim in donkeys, mules and horses. Am J Vet Res 2002;63:349 –353. 3. Coakley M, Peck K, Taylor T, et al. Pharmacokinetics of flunixin meglumine in donkeys, mules, and horses. Am J Vet Res 1999;60:1441–1444. 4. Welfare R, Mealey K, Matthews N, et al. Pharmacokinetics of gentamicin in donkeys. J Vet Pharmacol Ther 1996;19: 167–169. 5. Matthews N, Peck K, Taylor T, et al. Pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in clinically normal horses and donkeys. Am J Vet Res 1997;58: 53–55. 6. Matthews N, Peck K, Taylor T, et al. Pharmacokinetics of phenylbutazone and its metabolites in miniature donkeys. Am J Vet Res 2001;62:673– 675. 7. Matthews N, Mealey K, Taylor T, et al. Pharmacokinetics and cardiopulmonary effects of guaifenesin in donkeys. J Vet Pharmacol Ther 1997;20:442– 446. 8. Matthews N, Taylor TS. Anesthesia of donkeys and mules: how they differ from horses, in: Proceedings. 56th Annual Meeting of the American Association of Equine Practioners 2002;110 –112. 9. Matthews, N. Anesthesia and Analgesia for Donkeys and Mules. In: Muir, WW and Hubbell, JAE, ed. Equine Anesthesia: Monitoring and Emergency Therapy, 2nd ed. St. Louis: Saunders, Elsevier. 2009:353-357. a Rompun, Bayer Animal Health, Shawnee, KS 66201. Sedivet, Boehringer Ingelheim Vetmedica, St. Joseph MO 64506. c Dormosedan, Pfizer Animal Health, Exton, PA 10017. d Dormitor, Pfizer Animal Health, New York, NY 10017. e Promace, Fort Dodge Animal Health, Fort Dodge, IA 50501. f Torbugesic, Fort Dodge Animal Health, Fort Dodge, IA 50501. g Buprenex, Reckitt Benckiser Pharmaceuticals, Richmond, VA 23235. h Morphine sulfate solution, Baxter Healthcare, Deerfield, IL 60015. i Banamine, Shering-Plough Animal Health, Summit, NJ 07901. j Phenylbutazone Equi-Phar injection, Vedco, St. Louis, MO 64507. k Ketaset, Fort Dodge Animal Health, Fort Dodge, IA 50501. l Valium, Abbott Laboratories, Abbott Park, IL 60064. m Versed, Hospira, Lake Forest, IL 60045. n Rapinovet, Schering-Plough Animal Health, Summit, NJ 07901. o Sodium pentothal, Abbott Laboratories, Abbott Park, IL 60064. p Alfaxan, Vetoquinol UK Limited, Buckingham MK18 1PA, UK. q Telazol, Fort Dodge Animal Health, Fort Dodge, IA 50501. r Guaifenesin, Rood and Riddle Veterinary Pharmacy, Lexington, KY 40511. s Isoflurane USP, Halocarbon Products, River Edge, NJ 07661. t Sevoflo, Abbott Laboratories, Abbott Park, IL 60064. b