Scientific Proceedings Equine Programme
5
Anaesthesia in Donkeys (Equus asinus)
J.P.A.M. van Klein, DVM
Resident in Veterinary Anaesthesia and Intensive Care, Department of Equine
Sciences, Faculty of Veterinary Medicine, Utrecht, [email protected]
Introduction
This presentation will discus anaesthesia in donkeys and will focus on
the differences between horses
and donkeys. An introduction will
be given considering the diversity
that is found in donkey breeds.
There are small Mediterranean
donkeys weighing less than 80 kg,
while the largest breeds like the French Poitou can reach
the size of warmblood horses with a weight between
400 and 500 kg. Equus asinus has a varying number of
chromosomes from n=27 to n=31, while Equus caballus
(the horse) has 64 chromosomes. This is the reason for
the infertility of both mules and hinnies, the crossbreds
of horses and donkeys.
Anatomical differences
There are several anatomical differences of vital
importance when performing anaesthesia in donkeys (1).
Donkeys have small nasal passages and the pharynx is
angled differently compared to horses. Furthermore, the
pharyngeal recessus is very deep. This may not only give
problems with nasogastric intubation, but it may also
make tracheal intubation in donkeys more complicated.
The jugular vein is covered by a thick muscle (M. cutaneus
colli), which can make jugular venepuncture and
catheterisation difficult.
Physiological differences
Several physiological differences between horses and
donkeys exist as well. Donkeys are adapted to desert-like
circumstances and can loose up to 20% of their circulating
volume before signs of dehydration are evident. They
normally do not show an obvious fight and flight
reaction, are very stoic and do not show pain that easily.
Like Shetland ponies, donkeys are prone to develop
hyperlipaemia when they are starved (6). These differences
have consequences for perioperative food and energy
management and perioperative use of analgesics.
Isoflurane can be used for maintenance of anaesthesia in
the donkey. The MAC value for isoflurane is 1.3% for the
donkey. In the mule however, the MAC value is not
determined yet.
Cases of anaesthesia in donkeys that are performed at
the Equine Clinic, Faculty of Veterinary Medicine in
Utrecht are discussed and the anaesthesic protocols that
are used in this clinic will be discussed as well.
References:
1. Burnham SL. Anatomical differences of the donkey and mule. AAEP
Proceedings 2002;vol.48, p. 102-109.
2. Matthews NS, Taylor TS, Skrobarcek CL, Williams JD. A comparison of injectable anaesthetic regimens in mules. Equine Vet J
1992;suppl.11:34-36.
3. Matthews NS, Taylor TS, Hartsfield SM, Williams JD. A comparison
of injectable anaesthetic regimens in mammoth asses. Equine Vet J
1992;suppl.11:37-40.
4. Matthews NS, Taylor TS, Hartsfield SM, Hayton WL, Jones DH.
Pharmacokinetics of ketamine in mules and mammoth asses
premedicated with xylazine. Equine Vet J 1994;26(3):241-243.
5. Matthews NS, Taylor T, Hartsfield S. Anaesthesia of donkeys and
mules. Equine Vet Edu 1997;9:198-202.
6. Moore BR, Abood SK, Hinchcliff KW. Hyperlipemia in 9 miniature
horses and miniature donkeys. J. Vet Intern Med 1994;8(5):376-381.
7. Mostafa MB, Farag KA, Zomor E, Bashandy MM. The sedative and
analgesic effects of detomidine (Domosedan) in donkeys. JAVMA
1995;42:351-356.
Clinical pharmacology
Pharmacological differences between the horse and the
donkey are caused by differences in the cytochrome P450
iso-enzyme pattern and differences in the volume of
distribution for several anaesthetics. These pharmacological variations implicate different strategies for
anaesthesia in donkeys and mules when, for example,
alfa 2-agonists, ketamine or guaiphenesin (7, 2, 3, 4, 5) are
indicated.
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