CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
FIGURE 11-12 Tying the tourniquet around the arm.
Source: Delmar/Cengage Learning.
FIGURE 11-13 To release the tourniquet, pull on the end (marked
by an arrow).
Source: Delmar/Cengage Learning.
are performed where the median cubital, cephalic, and basilica veins are all found
close to the surface of the skin. Some veins are visible while others are prominent
but can only be felt by palpation with the index finger. Palpation also gives clues as
to the direction the vein travels and the size and depth of the vessel (Figure 11-14).
An artery has a detectable pulse and should not be used for ordinary purposes
of drawing blood. A vein that feels quite hard should be avoided since it may be
sclerosed (hardened) or thrombosed (contain a clot). Tendons are also found in the
joint region and are extremely hard. It would be painful for the patient if the phlebotomist
inadvertently punctured a tendon; as well, no blood would be obtained.
Hard veins “roll” more easily, and rotating the hand and wrist slightly will sometimes
place the vein in a more advantageous position for collecting blood.
Once all of these conditions have been considered, the venipuncture should
proceed.
Entering the Vein
Unsheath (remove the cover from) the needle just before performing the actual
entry through the skin. Leave the tube that should be drawn first lying loosely in
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