CLINICAL LAB SCIENEC

CHAPTER 11: PHLEBOTOMY 273
Table 11-3 Rationale for Order of Draw for Phlebotomy Procedures
Tube Stopper Color
Yellow
Red, plain
Blue
Camouflage (“tiger” or
mottled)
Red, with gel
Gold
Green
Pink, purple, lavender
Gray (grey)
Rationale for Order of Draw
Sterile; used for cultures of blood; top must be clean
No additives; used for drug analyses; lack of additives necessary to prevent
cross-reactions
Contains citrate, an anticoagulant; used for coagulation studies; binds
calcium and enables other clotting factors to be analyzed; calcium is added
for certain procedures
Has a barrier gel to separate liquid (serum) and solid components of blood
Has separator gel to separate liquid (serum) and solid components of blood,
but no other additives, in most cases
Has barrier gel and a clot enhancer; used when it is necessary to separate
the blood components quickly
Contains heparin, an effective anticoagulant; most often used in chemistry
testing where plasma is used as a sample; some green top tubes contain a
lithium gel that also separates plasma from cells and is a barrier additive;
small tubes for pediatric patients are available
Contain EDTA as an anticoagulant that preserves blood cell anatomy; most
often used for blood cell counts as this anticoagulant preserves the morphology
of the blood cells, whereas citrate and flouride anticoagulants will not
Contains sodium fluoride/potassium; used to preserve glucose values when
it is inconvenient to immediately perform a glucose procedure; the sodium
flouride/potassium oxalate in the tube preserves the glucose by preventing
metabolism by the blood cells, which would consume the glucose and
provide a falsely low value
the equipment and supplies you will need within easy
reach (Figure 11-4).
Choosing and Using the Appropriate Needle
Choose the correct needle gauge. Usually for the normal
patient, a 20- or 21-gauge needle is used (the
smaller the gauge, the larger the needle). The 20- or
21-gauge needle allows an adequate flow of blood.
Since the smaller-gauge needles may actually damage
blood cells, causing morphological changes in the red
blood cells and sometimes even lead to destruction,
smaller gauges for cell counts should be avoided when
and if possible. Screw the needle into the barrel, if reusable
barrel/needle devices are used, leaving the cover
on the needle outside the tube holder. Seat the first tube
in the tube holder but DO NOT push the tube onto the
internal needle, as the vacuum will be lost and it will be
impossible for blood to enter the tube.
FIGURE 11-4 Venipuncture supplies and equipment.
Source: Delmar/Cengage Learning.
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