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In-Depth Information
The technique has been validated in comparison to radiotelemetry
( 23 ) and carotid artery catheterization with some minor discrepancies.
For example, tail cuff measurements tend to be less reliable at the
extremes of both hypotension (<110 mmHg) and hypertension
(>180 mmHg) in the mouse ( 23, 24 ). Further studies in rats suggest
that the variability is greater than that seen in mice, with at least
one study demonstrating a 37 mmHg difference between tail cuff
and arterial cannulation with signifi cant variability from reading to
reading ( 17, 25 ). Additional drawbacks to this approach include
the need to minimize stress and stimuli which induce movement
(by training animals in the restrainers) as well as the need to main-
tain tail vasodilatation. Devices that minimize movement and
provide a warmed surface are available with most systems. The
need to maintain vasodilatation does present limitations in studies
of hypothermia as well as those experiments involving vasocon-
stricting pharmacologic agents.
Technique
Animals can be either awake or anesthetized
Holders are of different sizes and can hold animals weighing
anywhere between 8 and 950 g. Up to eight animals can be
recorded at the same time with some devices. Some investiga-
tors prefer to train animals in the restrainers a few days prior to
the experiment day to reduce stress.
Gently place animals in the restrainers and properly fi x their
noses on the nose cone holders at least 10-15 min before mea-
surements to allow time for acclimatization
The tail should be fully extended and should exit through the
rear hatch opening of the holder
Secure the cuff around the tail
A computerized system will record and display several pressure
parameters like systolic, diastolic, and mean BP, heart rate, tail
blood volume, and blood fl ow
2.2. Direct Arterial
Blood Pressure
Measurement Using
Exteriorized Catheters
Exteriorized catheters present a direct interrogation of arterial (or
venous) blood through direct cannulation of the vessel. The two
most common methods are the use of indwelling fl uid-fi lled cath-
eters and transducer-tipped catheters. Exteriorized catheterization
is reliable in most experimental approaches and offers a route
through which pharmacologic agents can be delivered and blood
samples collected. This is an invasive procedure that has signifi cant
risk for mobidity, depending on the vessel that is cannulated. It
also requires microsurgery skills and can prove quite diffi cult in
smaller rodents where vessel cannulation is a challenge. Additionally,
there is the increased risk for infection and complications of cath-
eter thrombosis. The effects of this invasive procedure on the phys-
iology of the animal must also be considered, especially in studies
requiring consciousness ( 26 ).
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