CLINICAL LAB SCIENEC

CHAPTER 11: PHLEBOTOMY 277
The tourniquet should never be so tight as to
arrest the flow of blood in the artery, which
lies deeper than the vein. Serious damage may
occur if this is done, even for a relatively short
period of time.
A tourniquet may be of several varieties.
Some patients may be aware of a latex
sensitivity and this type of tourniquet would
be avoided in these patients. Some medical
facilities avoid the problem by using only
latex-free tourniquets, or a cloth barrier that
is used along with the tourniquet. Some tourniquets
are designed with Velcro strips for
closure, while others are flat latex tubing or
strips. The latter type is placed on the arm as
a simple loop tucked or looped under so as to
allow pulling on one end to loosen the entire
tourniquet with a minimum of movement.
If the patient has large, visible veins, the
tourniquet will not need to be placed on the
arm and the vein checked by palpation before
the final application of the tourniquet.
Apply the tourniquet 3 or 4 inches above
the intended puncture site. When the tourniquet
is applied with the right tightness, the
vein should protrude slightly and enable a
pool of blood to collect in the vein for withdrawal,
as more blood can flow into the area
than is able to leave. If the tourniquet is too tight, the arteries may
be constricted and blood cannot flow into the area. If the tourniquet
is too loose, it is ineffective for “pumping up” the vein. A
tourniquet should feel only slightly tight for the donor and should
not be twisted or pinch the skin of the person. Do not apply the
tourniquet over areas with chafing, a rash, or an open sore. The
tourniquet is placed as shown in Figures 11-11, 11-12, and 11-13.
The site should be cleaned quickly with 70% isopropyl alcohol,
using circular motions while moving gradually farther from
the center, leaving a 2-inch square area that has been cleansed of
surface contaminants and loose cells.
Palpating for the Vein
After the tourniquet is properly placed and the skin is cleansed, the
patient is asked to make a fist, which serves to make the vein even
more prominent. Vigorously squeezing and loosening the fist may
cause hemoconcentration (higher density of blood cells) for some
tests, so pumping of the fist should be avoided. Veins will usually be
more easily visualized in the dominant arm. Phlebotomy procedures
FIGURE 11-11 Patient in donor chair with arm supports in place.
Source: Delmar/Cengage Learning.
Safety Alert
Safety in Applying a Tourniquet
Improper use of the tourniquet may:
• Affect concentration of certain test
analytes (components of blood being
tested for)
• Injure the fragile skin and tissues of
elderly patients if too tight
• Cause damage to an extremity (arm in
most cases) by leaving the tourniquet
on the arm for long periods of time
• Induce clot formation when the
tourniquet is left on a limb for an
extended length of time
• Cause bleeding around the site if
the needle is removed from the vein
while a tourniquet is still in place
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