Phlebotomy (blood drawing) in a rabbit
Esther van Praag, Ph.D.
Warning: this file contains pictures that may be distressing for
people.
Rabbits are easily
startled and may start scratching the manipulating person or jump from the
examination table during the clinical examination or a blood sample. They
often jerk in response to venipuncture in the marginal vein of the ear, when
the skin has not been anesthetized beforehand. As a result, rabbits should
therefore be restrained in a towel, bag or laboratory coat.
For a pictorial demonstration of
restraint in a towel, see: Safe immobilization of a rabbit in a towel (“rabbit
burrito”)
The amount of
blood needed for a blood test will determine the location where the sampling will
be done. Veins are used (venipuncture (blood from the vein is used), some
rare tests nevertheless require blood from the artery. Arteries, should,
however, be avoided as this procedure is painful and can lead to damage and
necrosis of the arterial vessel.
Amounts up to 5 ml of blood can be
safely drawn from the auricular marginal vein, using a 23- to 25-gauge needle
or a 23-gauge butterfly attached to a syringe or tube. It is also possible to
place a catheter-over-needle.
The preparation of the skin is identical,
independent of the collection method used. Before starting the sampling, the
fur on the ear is shaved, and the skin is cleaned with alcohol. As the skin
on the ear is very sensitive it is recommended to anesthetize the skin
locally with e.g. a lidocain containing cream (e.g.
EMLA®).
The creamed spot is wrapped with a
plastic sheet and a protective adhesive bandage. After 45 min., the full
thickness of the skin is numb. The anesthetic effect remains effective for
the next 60 min.
Dilation of the vessel can be obtained
by massage of the ear, approach of a heat source near the rabbit ear or by
using blood vessel dilating agents, e.g. acetylpromazine
(0.25 ml, SC).
After occlusion of the vein, the needle
is carefully inserted and blood can be withdrawn. The procedure must be done
slowly, in order to avoid hemolysis of the red blood cells (erythrocates), but should be fast enough to avoid the
formation of blood clots. After removal of the needle, a
cotton gauze is firmly applied on the site of venipuncture, during at
least 1 minute, or until bleeding has stopped, in order to prevent the
formation of hematomas and blood clots. The use of alcohol-impregnated gauze
should be avoided; alcohol causess vasodilatation
and prevents hemostasis.
Stain of blood on the ear can be
removed with hydrogen peroxide
The rabbit should remain under
observation over the next hours to ensure that hemostasis is complete.
The jugular vein
can be used to collect a fairly big amount of blood. The dewlap of female
rabbits does not represent a hindrance. The rabbit can be placed in several
positions, in order to collect blood from the jugular vein:
- sternal
recumbency, with the neck extended upwards and the front limbs hanging over
the end of the examination table;
- dorsal recumbency,
after safely restraining the rabbit in a towel, and extending the neck in
order to expose the jugular vein;
- lateral
recumbency, with the neck extended out and the front legs pulled downward.
The jugular vein
should be avoided for blood collection if the rabbit suffers from a
respiratory problem or shows respiratory distress. It may become cyanotic
during the procedure.
Alternate sites
for blood collection are the cephalic and the lateral saphenous
veins. Their locations are the same as in dogs and cats. These veins are
fragile, and a hematoma is easily formed.
Collection of blood from the central
artery must be avoided, unless higher volumes of blood need to be collected.
This site is painful and often leads to subsequent distal ischemia, due to
impairment of blood supply to the pinna after the
formation of a hematoma or due to blood vessel damage (arterial trauma with
thrombosis). A collapse of the vessel may, furthermore, occur when excessive
pressure is exerted. If the use of the central artery cannot be avoided, the
21-gauge needle should be inserted as distally (tip of the ear) as possible
into the artery. The blood should start to flow immediately in the syringe.
Complete blood count and biochemistry reference values in
rabbits
Acknowledgement
Thanks are due to
Akira Yamanouchi (Veterinary Exotic Information
Network), for the permission to his photograph.
Thanks are also due
to my rabbits Grijsje, Flora and Stampi, for their patience.
Further
information
Mc Guill, M.W. and
Rowan, A.N. (1989) Biological effects of blood loss: implications for
sampling volumes and techniques. ILAR NEWS 31, No. 4, 5-18.
Exotic Companion Medicine Handbook for
Veterinarians, Cathy Johnson-Delaney and Linda Harrison
Mader DR. Rabbits - basic approach to veterinary
care. In: Hillyer EV, Quesenberry
KE (eds.): Ferrets, Rabbits, and Rodents - Clinical Medicine and Surgery. Philadelphia,
WB Saunders, 1997: 160-168.
Paul-Murphy J, Ramer JC. Urgent care of the pet rabbit. In: Rupley
AE (ed.): Vet Clin North Am (Exotic Anim Pract). Philadelphia, WB
Saunders, 1998: 127-152.
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