CLINICAL LAB SCIENEC

CHAPTER 13: HEMATOLOGY AND COAGULATION 343
A
B
FIGURE 13-10 Filling a capillary tube from (A) a sample of anticoagulated blood and (B) a capillary puncture.
Source: Delmar/Cengage Learning.
4. Wash hands properly with soap and water, using friction by rubbing the hands
together. After washing hands and before beginning the procedure, put on gloves
made with nitrile or other nonallergenic materials.
5. Swab the tip of one of the patient’s less-used fingers, such as the ring finger on
the nondominant hand, with alcohol.
6. With a lancet, prick the finger tip with a quick firm jab to the side of the fingertip
(or use a device such as an Autolet).
7. Immediately discard the lancet in the sharps container.
8. Use a clean dry cotton ball to wipe off the first drop of blood that appears. It is
important to wipe the first drop from the finger as fluid from the tissues may create
inaccuracies in the reading as well as cause the puncture to stop bleeding
prematurely.
9. Fill a heparinized capillary tube 75% full with blood by slightly tipping it to allow
blood to flow downhill into the tube (Figure 13-10B).
a. Capillary action will naturally aid in this filling.
b. Lightly “milk” the finger by placing your index finger around the patient’s finger
tip, but avoid squeezing. Intense squeezing will cause more rapid clotting and
a cessation of the blood flow due to coagulation factors in the skin. Also avoid
bubbles, which will appear as skip marks in the tube.
10. Hold the tube horizontally and press the filled end into the sealing putty (Critoseal)
to plug the end. Critoseal trays are designed with small holes to store the
filled capillary tubes until they are ready to be centrifuged. Collect any additional
samples needed for other tests before clotting occurs.
11. Collect and prepare a second tube to be averaged with the result of the first.
12. Lay the tubes in the centrifuge Hct head with the plugged ends to the outside
to avoid the blood spinning out of the tube. Record the numbered slots for each
sample. A tube should be used as a balancing Hct tube when there is only one
tube being spun, or if there is an uneven number of tubes that would leave an
empty slot across from a tube to be spun.
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