Download How to Anesthetize Donkeys for Surgical Procedures in the Field

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
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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