105

7

Blood c ollection p rocedures

For most large species blood is collected using a needle and syringe or vacuum technique governed by the size of animal and the volume of blood required. Where repeated samples are required there are advantages associated with taking blood from one site only; for example, profi ciency with one regularly used tech-nique will improve sample quality. Consistency in bleeding technique and site means that data will be comparable with those obtained at different time points; different bleeding sites may produce differing cell counts masking dynamic changes in cell numbers. It is therefore critical for a laboratory to establish its own typical ranges using its preferred bleeding site, method of collection, analytical methods, etc.

Common b leeding s ites

Rodents present special problems because of their small blood vessels. Retro - orbital sinus bleeds have been a popular site of choice, while tail vein bleeds on restrained unanesthetised animals are now more common. Cleaning of the tail is important to avoid contamination of the sample by epidermal cells or bacteria. Tail transection will provide little more blood than is suffi cient for a blood fi lm. Cardiac puncture has been used where larger volumes are required, although this method should be reserved for post-mortem collection.

The preferred venipuncture site for rabbits is an ear vein. Dogs are conveniently phlebotomised from the jugular vein, although the cephalic vein is also used. Primates are conveniently phlebotomised from the femoral vein.

Atlas of Comparative Diagnostic and Experimental Hematology, Second Edition. Clifford Smith, Alfred Jarecki.© 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

Table 7.1 lists commonly used sites. Hazards include the use of anesthesia, accidental collection of mixtures of arterial and venous blood and tissue fl uid contami-nation. The quality of the samples is especially depend-ent on the care taken during collection.

Anticoagulants

Once blood has been obtained it must be transferred immediately to an anticoagulant if cell counts or mor-phology are to be examined. For routine hematology cell counts and blood fi lms, di - potassium or tri - potassium salts of EDTA are preferred; other antico-agulants should be avoided for routine cell morphology due to artifactual changes, e.g. platelet clumping, dilu-tion, background staining, etc. Heparinised syringes may be of help and induce minimal morphological changes in obtaining samples from slow - bleeding animals.

Staining

Romanowsky stains, used for most of the illustrations in this atlas, are appropriate for most species without modifi cation. Leishman ’ s, modifi ed Wright ’ s, Jenner ’ s and May – Gr ü nwald – Giemsa stains are equally suita-ble; personal preference will dictate which particular stain is used for routine examinations. Correct fi xa-tion and staining are important and critical to the interpretation of abnormalities. Where abnormalities are fl agged by an automatic analyser it will be neces-sary to examine a manually prepared blood fi lm stained by conventional techniques for confi rmation.

Tabl

e 7.

1 Co

mm

on b

lood

col

lect

ion

sites

.

Bloo

d co

llect

ion

site

Spec

ies

Mou

se

Ham

ster

G

uine

a pi

g Ra

t Ra

bbit

D

og

Cat

M

ini - p

ig

Mon

key

Hor

se/c

ow

Tail

vein

–

–

–

#

–

–

–

–

–

–

Tail

tran

sect

ion *

#

–

–

#

–

–

–

–

–

–

Subl

ingu

al

–

–

–

#

–

–

–

–

–

–

Abd

omin

al a

orta

* *

#

#

#

#

–

–

–

–

–

–

Retr

o - or

bita

l sin

us

–

–

–

#

–

–

–

–

–

–

Car

diac

pun

ctur

e * *

#

#

#

#

–

–

–

–

–

–

Jugu

lar

vein

–

–

–

#

#

#

–

#

#

#

Cep

halic

vei

n –

–

–

–

–

#

#

–

–

–

Mar

gina

l ear

vei

n –

–

–

–

#

–

–

–

–

–

Fem

oral

vei

n –

–

–

–

–

–

–

–

#

–

* Use

ful f

or b

lood

sm

ear

prep

arat

ion

only

. * *

At

term

inat

ion.

106