HKD1522009
Importance of injection site for coronary blood
flow determinations by microspheres in rats
PIERRE WICKERAND ROBERT C.TARAZI
ResearchDivision,TheCleveland ClinicFoundation,Cleveland,Ohio44106
WicKER, PiERRE, AND RoBERT C. TARAzi. Importance of put) and regional (coroniary, renal, cerebral) flows. The
injection site for coronary blood flow delerminations by micro.results show that 1) intra-atrial injections leadmore
spheres in rats.Am.J.Physiol.242(Heart Circ.Physiol.11):
H94-H97,1982.-Because coronary blood flow (CBF) deter.
consistently to adequate dispersion ofthe microspheres
minations require that blood and microspheres be uniformly
in the aortic root than do intraventricular injections and
mixed in the root of the aorta,we developed a echnique of left.
2) the intra-atrial-injection technique must be preferred
atrial (LA) catheterization in rats and compared the variability
for precise deterininations of coronary blood flow because
ofresults obtained by LA injection and left-ventricular (LV)
of the lower variability resuiting from better mixing of
themicrospheres.
(coronary), and distal (renal, cerebral) flows in anesthetized
animals. CBF values averaged 410 ± 224 and 358 ± 99 (SD) ml.
min'.100 g′ from LV and LA injection,respectively,or 5.7 ±
METHODS
2.9 and 4.9 ± 1.3(SD) %CO. The variability with LA injection
Experiments were carried out in anesthetized rats sep-
was significantly lower than with LV injection as shown by the
marked differences in standard deviations obtained with the
arated into two groups. In group A (n = 10) the micro-
spheres were injected first into theleft atrium and sub.
P > 0.o1). In contrast, no significant difference in variability
sequently into the left ventricle.In group B (n = 10) the
was found for either CO or more distal regional fows. These
left-ventricular injection was performed first followed by
results indicate thatLV injectionsmight beadequate for sys-
the intra-atrial injection. The sequence of studies was
temicflowandregionalflowstorelativelydistalbedsbutthat
regularly alternated so that one animal of group A (left-
accurate measurements of CBF require LA injection of micro-
atrial injection first) was followed by one of group B
spheres.
(left-ventricular injection first).
Preparation of rats. Sprague-Dawley rats were anes-
cardiac output;regional blood flow; left-atrial catheterization
thetized with pentobarbital sodium (30 mg/kg ip),and
anesthesia was subsequently maintained with small doses
SINCE ITs INTRoDUcrION in 1967 by Rudolph and Hey-
30-45 min.The rats were intubated through the mouth
mann (13), the microsphere method has been extensively
and ventilated with room air. The same surgical sequence
used because of its simplicity and the possibility of de-y
was used in all animals whatever the order of injection.
termining regional as well as systemic blood flow even in
First, a catheter was positioned in the left atrium. The
small animals like rats (7-9, 11, 14). However, the accu-
left-atrial appendage was exposed by thoracotomy
racy ofresults from microsphere injections depends fun-
through the third left intercostal space,the pericardium
damentally on the uniform mixing of microspheres in the
was opened, and a PE-10 tubing was advanced through
bloodstream; in that respect the site of injection may be
a small cut of the lateral wall of the appendage, secured
critical, particularly for coronary blood flow mieasure- in place, and passed through the chest wall along the
ments. Because of alleged difficulties of left-atrial cathe-
sternum. The chest was closed after lung expansion by
terization, most studies of rats have utilized a left-ven-
positive-intratracheal pressure while a negative pressure
tricular approach, assuming in the process that mixing
was applied to the thoracic cavity. The animal was dis.
was adequate (7, 9, 12, 14). However, experiments in dogs
connected from the respirator, and the rest of the exper-
have shown that left-ventricular injections give less de-
iment was performed while the rat was breathing spon.
pendable results and more marked differences in the
taneously.
distribution of microspheres to the heart than injections
Two catheters (made up of a 3- to 4-cm-long Teflon
into the left atrium (2, 5). Moreover our preliminary
tubing inserted into a PE-50 tubing) were then advanced
experiments in rats did show a high variability of coro-
3 and 3.5 cm in the aorta through a right. and left.
nary blood flow measurements with left-ventricular in-
femoral-artery cannulation, respectively. The right-fem.
jections.We therefore developed a technique of left-atrial
oral catheter was cornected to a Micron MP-15 trans-
catheterization in rats that could be performed with no
ducer for blood pressure recording. The left catheter was
major technical difficulties. This allowed us to compare
used to withdraw blood. A PE-i0 tubing catheter was
the variability of blood flow dete:minations made by left-
finally inserted into che right-carotid artery.
atrial injections with that of measurements obtained by
In group A the carotid catheter was aavanced into the
left-ventricle injection, as regards systemic (cardiac out.left ventricle under blood pressure control after the left-
NH
0363-6136/8/0000-0000s01.25Copvright1982theAmericanPhysiologiralSociety
