How to Anesthetize Donkeys for Surgical Procedures in the Field

DRUGS AND ANESTHESIA

Lori A. Bidwell, DVM, Diplomate ACVA

1. Introduction ing a local block where a catheter will be placed and Donkeys are an important part of the work force in making a small skin incision with a surgical blade much of the world. Practitioners working with before placing an intravenous catheter is recom- donkeys in the United States and those participat- mended. Intubation is more difﬁcult because of ing in equitarian initiatives abroad should under- caudal angulation of the larynx, a pharyngeal diver- stand the difference between donkeys and horses in ticulum, excess pharyngeal mucosa, and long paired relation to anesthesia. Although it is tempting to laryngeal saccules. Additionally, nasal intubation 1 treat a donkey like a horse, there are important is complicated by narrow nasal passages. Drug differences in relation to handling and drug doses. metabolism is elevated in donkeys compared with Additionally, it is important to understand alterna- horses, resulting in the use of higher doses and more 2–6 tive anesthetic protocols because a practitioner may frequent dosing intervals. The only known ex- be limited to minimal or alternative drugs when ception to this is the administration of guaifenesin, working in a developing country. which seems to require lower dosing because respi- ratory arrest is easy to achieve when using doses 7 2. Behavior and Physiology appropriate for a horse. A tame donkey can be easy to handle but a feral or minimally handled donkey can be frustrating. 3. Sedation and Analgesia Donkeys are intelligent and typically take little time Xylazine,a romiﬁdine,b detomidine,c and dexmedeto- and handling to tame and train. They tend to lean midined have been safely administered to donkeys into pressure and lean against a pulling force; there- using doses similar to those administered to horses fore, the best technique for moving a donkey is gen- with sedation and analgesia of duration shorter tle coercion. Anatomic and physiologic differences than or similar to that in horses. Personality and make intravenous injection, orotracheal intubation, demeanor should dictate which part of the dose and drug dosing more complicated. The cutaneous range you select when determining a protocol (Table colli muscle extends over the jugular furrow and can 1). If intramuscular dosing is required, it is recom- hinder visibility when distending the vein, compli- mended to double the intravenous dose for a similar cating venepuncture or catheter placement. Plac- effect. In a calm, tame donkey, xylazine can be

NOTES

38 2010 ր Vol. 56 ր AAEP PROCEEDINGS DRUGS AND ANESTHESIA

Table 1. Recommended Drug Doses for Sedation, Induction, Maintenance, and Analgesia of Donkeys

Dose Route of Administration Expected Duration

Sedation Xylazine 0.8 mg/kg (0.3–1.0 mg/kg) IV, IM 15–20 min Romifidine 0.08 mg/kg (0.05–0.1 mg/kg) IV, IM 30 min to 2 h (duration is dose dependent) Detomidine 0.01 mg/kg (0.005–0.04 mg/kg) IV, IM, sublingual 20–40 min (duration is dose dependent) Dexmedetomidine 0.005 mg/kg (0.0025–0.01 mg/kg) IV, IM 20–30 min (duration is dose dependent) Acepromazine 0.03 mg/kg (0.02–0.05 mg/kg) IV, IM, sublingual 30 min to 2 h Induction Ketamine 2.5 mg/kg IV 10–15 min Diazepam/midazolam 0.05 mg/kg (0.02–0.08 mg/kg) IV 10–15 min Propofol 2.0 mg/kg IV 10–15 min Alfaxalone 2.0 mg/kg IV 10–15 min Thiopental 8.0 mg/kg IV 20 min Telazol 1.0 mg/kg IV 20 min Maintenance Triple drip 12.5 g guaifenesin IV (requires an IV catheter) Infusion lasts ϳ45 min 500 mg ketamine Administering a bolus 150 mg xylazine often results in apnea. (combined in a 500-ml bag of LRS or 0.9% NaCl) Analgesics Butorphanol 0.03 mg/kg (0.02–0.05 mg/kg) IV, IM 30–50 min Buprenorphine 0.006 mg/kg IV, IM, sublingual 6 h Morphine 0.01 mg/kg IV, IM 2–3 h dosed at 0.8 mg/kg (range, 0.3–1 mg/kg) IV or romi- should be administered at 2.5 mg/kg and is more fidine administered at 0.08 mg/kg (range, 0.05–0.1 effective when combined with diazepaml or midazo- mg/kg) IV. Detomidine can be given at 0.01 mg/kg lamm at 0.05 mg/kg (range, 0.02–0.08 mg/kg) IV. (range, 0.005–0.04 mg/kg) IV, and dexmedetomidine Propofoln produces smooth induction and recovery can be dosed at 5 ␮g/kg (range, 2.5–10 ␮g/kg) IV, with anesthesia that lasts ϳ10–15 min when ad- with sedation lasting 20–30 min. Acepromazinee ministered at 2.0 mg/kg IV. Thiopentalo adminis- can be administered with an ␣-2 agonist if the don- tered at 8.0 mg/kg IV produces anesthesia that lasts key is agitated or anxious at 0.03 mg/kg (range, ϳ20 min with slow recovery. Alfaxalone,p a drug 0.02–0.05 mg/kg) IV or IM. Adding butorphanolf to that is currently not approved for use in the United an ␣-2 agonist produces superior sedation and anal- States but is approved in Europe and Australia, can gesia at a dose of 0.03 mg/kg (range, 0.02–0.05 mg/ be administered at 2.0 mg/kg IV, with anesthesia kg) IV or IM. Buprenorphineg can be administered lasting 10–15 min. From experience, recovery at 0.006 mg/kg IV, IM, or sublingual. This drug from alfaxalone in donkeys is slow, with muscle does not produce sedation when given alone and can fasciculations and weakness. Miniature donkeys result in excitement if given to a donkey without an are similar to standard donkeys, although telazolq ␣-2 agonist. From observation, the analgesia asso- (the combination of tiletamine and zolazepam) has ciated with buprenorphine lasts ϳ6 h. Morphineh been used with success and is recommended for in- can also be administered to donkeys at 0.01 mg/kg duction at 1.0 mg/kg IV.9 The duration of anesthe- IV or IM, and the analgesic effect lasts ϳ2–4 h. sia using any of these anesthetic protocols can be The administration of non-steroidal anti-inflamma- extended by 3–5 min with an additional IV bolus of tory drugs like flunixin megluminei and phenylbu- the induction agent at one third the initial dose. tazonej are effective for post-operative pain, It is important to protect the donkey’s eyes while although studies have found that metabolism is anesthetized. Most induction techniques maintain faster in donkeys than horses, and therefore, dosing a blink reflex, but it is not always adequate to pre- intervals should be increased to three times a day vent ulceration of the cornea. Sterile ophthalmic rather than twice a day.3,5,6,8 Local anesthetics lubricant should be applied to the eyes and a towel have similar application and duration in donkeys as should be placed under the down eye to prevent those used in horses. contamination with grass, soil, or shavings.

4. Induction 5. Maintenance Induction agents that are used in horses can be used The combination of guaifenesin,r ketamine, and xy- in donkeys at similar doses. Dosing of ketaminek lazine, known as “triple drip,” can be used as main-

AAEP PROCEEDINGS ր Vol. 56 ր 2010 39 DRUGS AND ANESTHESIA tenance anesthesia for donkeys. Because of sensi- tain anesthesia for longer procedures. Recovery is tivity to guaifenesin, a solution of 12.5 g guaifenesin, typically smooth and without complications, but 500 mg ketamine, and 250 mg xylazine in a 500-ml simple assistance can prevent premature attempts bag of saline or lactated Ringer’s solution (LRS) is at recovery. recommended. This combination can be adminis- As more equine practitioners are working abroad tered after induction at 1 drop/s initially and then in equitarian programs or at home on client don- given to effect as depth of anesthesia changes. keys, it is important that they are comfortable anes- This combination will last for a minor surgical pro- thetizing these patients. cedure that takes ϳ45 min. A fast bolus of this combination will result in apnea, and therefore, cau- References and Footnotes tion should be used during administration. If a 1. Lindsay FE, Clayton HM. An anatomical and endoscopic portable foal or small animal anesthetic machine is study of the nasopharynx and larynx of the donkey (Equus available, miniature and standard donkeys can be asinus). J Anat 1986;144:123–132. intubated and maintained on isofluranes or sevoflu- 2. Peck K, Matthews N, Taylor T, et al. Pharmacokinetics of t sulfamethoxazole and trimethoprim in donkeys, mules and rane using anesthetic concentrations similar to horses. Am J Vet Res 2002;63:349–353. horses. 3. Coakley M, Peck K, Taylor T, et al. Pharmacokinetics of Intubation is more complicated than in horses but flunixin meglumine in donkeys, mules, and horses. Am J can be achieved by extending the head in a straight Vet Res 1999;60:1441–1444. 4. Welfare R, Mealey K, Matthews N, et al. Pharmacokinetics line along the dorsal surface of the donkey. A bite- of gentamicin in donkeys. J Vet Pharmacol Ther 1996;19: block (typically PCV piping) can be placed between 167–169. the incisors, with the endotracheal tube placed 5. Matthews N, Peck K, Taylor T, et al. Pharmacokinetics of through the block to the point of resistance at the phenylbutazone and its metabolite oxyphenbutazone in clin- larynx. Advancing the tube with gentle manipula- ically normal horses and donkeys. Am J Vet Res 1997;58: 53–55. tion during inhalation will often result in intuba- 6. Matthews N, Peck K, Taylor T, et al. Pharmacokinetics of tion. If there is resistance, retract the tube to the phenylbutazone and its metabolites in miniature donkeys. oral cavity, rotate 180°, and try again. Am J Vet Res 2001;62:673–675. 7. Matthews N, Mealey K, Taylor T, et al. Pharmacokinetics 6. Recovery and cardiopulmonary effects of guaifenesin in donkeys. J Vet Pharmacol Ther 1997;20:442–446. Donkeys typically recover from anesthesia in a calm 8. Matthews N, Taylor TS. Anesthesia of donkeys and mules: manner, rolling into sternal until they are alert and how they differ from horses, in: Proceedings. 56th Annual capable of standing on the first attempt. Most don- Meeting of the American Association of Equine Practioners keys will recover unassisted without complication, 2002;110–112. 9. Matthews, N. Anesthesia and Analgesia for Donkeys and but they can be assisted in recovery if necessary. Mules. In: Muir, WW and Hubbell, JAE, ed. Equine Anesthe- Because of small size, they are relatively easy to sia: Monitoring and Emergency Therapy, 2nd ed. St. Louis: restrain in a lateral position by placing a knee or Saunders, Elsevier. 2009:353-357. both knees on the dorsal neck and pulling their head toward you to prevent the momentum needed to aRompun, Bayer Animal Health, Shawnee, KS 66201. stand. Grabbing the tail for assistance and giving bSedivet, Boehringer Ingelheim Vetmedica, St. Joseph MO it a boost when they do attempt to stand is tolerated 64506. cDormosedan, Pfizer Animal Health, Exton, PA 10017. and effective as they tend to stand front end first. dDormitor, Pfizer Animal Health, New York, NY 10017. ePromace, Fort Dodge Animal Health, Fort Dodge, IA 50501. 7. Results fTorbugesic, Fort Dodge Animal Health, Fort Dodge, IA 50501. These techniques have been used with success in gBuprenex, Reckitt Benckiser Pharmaceuticals, Richmond, VA ϳ500 anesthetic cases per year run by veterinary 23235. hMorphine sulfate solution, Baxter Healthcare, Deerfield, IL students in a university setting. All protocols and 60015. procedures were approved by an Institutional Ani- iBanamine, Shering-Plough Animal Health, Summit, NJ mal Care and Use Committee. 07901. jPhenylbutazone Equi-Phar injection, Vedco, St. Louis, MO 8. Discussion 64507. kKetaset, Fort Dodge Animal Health, Fort Dodge, IA 50501. Donkeys can be easy to work with if you understand lValium, Abbott Laboratories, Abbott Park, IL 60064. their personality traits and recognize that they are mVersed, Hospira, Lake Forest, IL 60045. not horses in their responses to handling and drug nRapinovet, Schering-Plough Animal Health, Summit, NJ metabolism. Pre-medication dosed appropriate for 07901. oSodium pentothal, Abbott Laboratories, Abbott Park, IL temperament will result in sedation for standing 60064. procedures and induction of anesthesia. Induction pAlfaxan, Vetoquinol UK Limited, Buckingham MK18 1PA, produces anesthesia lasting between 10 and 20 min UK. with a variety of anesthetic agents used for horses or qTelazol, Fort Dodge Animal Health, Fort Dodge, IA 50501. rGuaifenesin, Rood and Riddle Veterinary Pharmacy, Lexing- agents commonly used for small animal patients. ton, KY 40511. The combination of guaifenesin, ketamine, and xy- sIsoflurane USP, Halocarbon Products, River Edge, NJ 07661. lazine or inhalant anesthetic can be used to main- tSevoflo, Abbott Laboratories, Abbott Park, IL 60064.

40 2010 ր Vol. 56 ր AAEP PROCEEDINGS