"Donkeys are becoming more common patients for equine veterinarians, and although it is tempting to treat a donkey like a horse, there are important differences regarding patient handling and drug dosages," cautioned Lori Bidwell, DVM, of Lexington Equine Surgery and Sports Medicine in Kentucky. Bidwell spoke on the key differences between anesthetizing donkeys and horses at the 2010 American Association of Equine Practitioners Convention, held Dec 4-8 in Baltimore, Md.
She started by listing several behavioral and physiologic differences between the two equids:
- Donkeys behave differently than horses (their behavior is often closer to that of cattle rather than horses);
- The musculature in the donkey's neck can make accessing the jugular vein more difficult in donkeys, which complicates the process of inserting a catheter for general anesthesia. A local anesthetic and surgical incision can help veterinarians place an intravenous catheter more easily;
- The angle of the larynx at the back of the throat (top of the trachea) is different than in horses, and donkeys have a pharyngeal diverticulum (pocket) in their throat, excess tissue in their pharynx, and elongated laryngeal saccules (part of the airway that aids in vocalization). Together, these anatomical differences make placing an endotracheal tube through the mouth to the trachea more difficult; and
- Nasal intubation also is more challenging because donkeys have narrower nasal passages than horses.
Also, higher doses (typically 1.5 times the horse dose) of a number of drugs are needed in donkeys. "One notable exception is guaifenesin (a centrally acting muscle relaxant). Horse doses of this drug in donkeys can cause respiratory arrest," Bidwell warned.
In general, all of the same types of drugs can be safely used in both horses and donkeys. This includes sedatives (e.g., xylazine and detomidine, which are used to sedate horses for standing surgeries), drugs used to induce or maintain general anesthesia (e.g., ketamine, diazepam), and drugs for pain management (e.g., butorphanol, morphine).
"Donkeys can be easy to work with if everyone appreciates that they are not horses," concluded Bidwell.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.