Page 270 - Cardiac Nursing

66.
66.
q
ara
5-2
5-2
q
6
6
6
q
xd
xd
24
a
a
In
t
ara
a
In
c.
p
24
ara
a
c.
e 2
e 2
46
g
g
g
46
p
p
t
A
A
p
Pa
/09
1
1
/29
/29
/09
0:2
M
M
Pa
0:2
1 P
1 P
0-c
0-c
11_
11_
K34
LWB
LWBK340-c11_ p pp245-266.qxd 6/29/09 10:21 PM Page 246 Aptara Inc.
K34
LWB
246 P A R T III / Assessment of Heart Disease
ports. The use of an indwelling intravascular catheter allows ac- person performing the procedure should be gloved. Syringes, used
cess to the patient’s blood supply without further invasive pro- once, should be discarded.
cedure. Comfort for the patient, ease, and speed of periodic
specimen collection are some of the benefits of using an in- Types of Specimens
travascular line for blood sampling. Intravascular catheters may
be kept patent by continuous or intermittent infusion, or by in- When blood is withdrawn from the body, it eventually clots. The
stilling saline or heparin solutions. Sometimes, solutions deliv- fluid that separates from the clot is called serum. Plasma, from un-
ered through the catheter may contain medications. The in- clotted blood, contains fibrinogen, which is eventually converted
fusate or any additives may dilute blood constituents. This to fibrin. Most blood tests are done on serum, and therefore re-
dilution would have the effect of lowering the concentration of quire use of a tube that allows blood to clot. Red-top tubes con-
the desired sample. tain no additives; they are used for chemistries, drug monitoring,
The diameter and length of the catheter are important deter- radioimmunoassays, serology, and blood typing. Lavender-top
minants when collecting blood specimens. The institution’s policy tubes, which contain ethylenediaminetetraacetic acid (EDTA), are
and procedure manual should be consulted for recommended usually used for hematology and certain other chemistries. Green-
withdrawal and discard from vascular devices. Additional sources, top tubes contain heparin as the anticoagulant and can be used for
such as professional nursing society standards, may assist in mak- chemistries, arterial blood gases, hormone levels, and some im-
ing decisions about recommended discard volumes. mune function studies. Blue-top tubes, used for coagulation stud-
Whether sampling from a pulmonary artery catheter, central ies, contain citrate. Sodium fluoride, found in gray-top tubes, pre-
venous line, arterial catheter, or other intravascular catheter, at- vents glycolysis and may be used to test blood glucose in its in vivo
tention should be paid to the feasibility of interruption of the state. 2
system. The pulmonary artery catheter presents particular prob- When multiple blood samples are drawn at the same collection
lems. Both the right atrium (RA) port and venous infusion port time, the preferred order is as follows: blood culture tubes, tubes
(VIP) are useful for the administration of drugs and fluids. Al- with no preservative (red-top); tubes with mild anticoagulants
though the RA port allows access to the central circulation, use (blue then green); tubes with EDTA (lavender-top); and ox-
of this port for thermodilution cardiac output calculations alate/fluoride tubes (gray-top) should be collected last. Blood for
makes it difficult to infuse drugs or fluids (a large amount of the coagulation studies should never be drawn first because tissue in-
infusate might be delivered during delivery of the cardiac out- jury can initiate the clotting process and result in falsely low lev-
put injectate). Consequently, the VIP is chosen for fluid and els of coagulation factors. Specimens in tubes with additives
drug infusion. In this situation, the use of the RA port may be should be rotated gently to mix the anticoagulant with the blood
preferable for blood withdrawal. If vasoactive drugs are not in- and should never be shaken. 2
fusing through the VIP, it may also be used for blood sampling. Hemolysis refers to the lysis of red blood cells (RBCs). When
The proximal opening into the RA is upstream of any drugs or extracellular fluid (plasma) is used for analysis, inaccurate results
fluid infusing through the RA port; therefore, the possibility of are produced if the specimen is hemolyzed. Hemolysis may occur
contamination of the blood sample by infusates is minimized. in vivo, as in hemolytic disease states such as transfusion reac-
Typically, the distal port of the pulmonary artery catheter is tions. Hemolysis may also occur in some infections and with the
only used for blood sampling when measuring a mixed venous use of some drugs. A deficiency of the enzyme glucose-6-phos-
blood gas from the pulmonary artery where venous blood mixes phate dehydrogenase, responsible for generating chemicals
after circulating through the superior and inferior vena cavae, needed for maintenance of normal red cell fragility, contributes
coronary sinuses, and the chambers in the right side of the to hemolysis.
heart. Hemolysis may also occur as a result of improper specimen
Many institutions have shifted to the use of saline in lieu of collection technique or specimen transport. Hemolysis is the
heparin in IV lines and pressure tubing however, questions persist cause for specimen rejection in most nonemergent situations.
about appropriate discard from vascular catheters (instilled with Specimens may be hemolyzed if they are collected from a poorly
heparin) when drawing blood for coagulation studies. Inconsis- flowing venipuncture. The selection of the appropriate size nee-
tent results may increase the cost to the patient through repeated dle and catheter is essential when performing venipuncture. Fail-
testing, wasted blood, or erroneous treatment decisions. Again, ure to dry alcohol from the venipuncture site also results in he-
the nurse may refer to policy and procedure manuals or profes- molysis. Blood should never be forcibly withdrawn from the
sional organization standards for guidance. In any event, coordi- venipuncture, nor should it be forcibly entered into the collec-
nation in obtaining multiple blood specimens decreases the tion tube by pushing on the syringe barrel to fill faster. Specimens
amount of blood that is eventually discarded and the number of should be handled carefully when placed in collection tubes and
times that the sterile system is invaded, thus reducing risk of in- when transported to the laboratory; rough handling may lead to
troducing infection. hemolysis.
Sepsis has been associated with intravascular monitoring Hemolysis increases the laboratory values of creatine kinase
2
equipment including stopcocks and pressure transducers, which (CK), potassium, magnesium, calcium, and phosphorus. He-
may be the most frequent reservoirs for endemic contamination. molysis invalidates the results of most coagulation tests and can
The incidence of local infection and bacteremia has been reduced mask hemolyzing antibodies in the antibody screen and cross-
2
by the use of disposable transducers and the percutaneous sheath match. If unexpected elevated laboratory values are reported, the
systems used to introduce pulmonary artery catheters. The with- blood should be redrawn if hemolysis is suspected.
drawal of blood from an intravascular catheter should be consid- Nursing research continues to evaluate different techniques
ered a sterile procedure. Once removed, caps used to cover stop- and equipment in determining the best method to withdraw
cock openings should always be replaced with a sterile cap. The blood, obtain accurate results, and reduce hemolysis. Contro-