Art: 714372-00L Rev. Date: 30-Jul-12 10-7
INDWELLING LINE
Blood Gas,
Electrolyte,
Chemistry
Back flush line with a sufficient amount of blood to remove intravenous
solutions, heparin or medications that may contaminate the sample. Five to
six times the volume of the catheter, connectors and needle is recommended.
Coagulation
Cartridges
If blood must be drawn from an indwelling line, possible heparin
contamination and specimen dilution should be considered. The line should
be flushed with 5mL of saline and the first 5mL of blood or six dead space
volumes of the catheter should be discarded.
SKIN PUNCTURE
Device
Use a puncture device that provides free-flowing blood. Inadequate blood
flow may produce erroneous results.
Hemolysis
Avoid hemolysis (bursting of red cells) due to vigorous massaging or “milking.”
Hemolysis will cause an increase in potassium results and a decrease in calcium
results.
To increase blood flow, massage a finger gently from about three inches from the
tip to the fleshy portion of the tip.
Avoid hemolysis by allowing residual alcohol to dry over the puncture site.
Tissue Fluid
For tests other than PT/INR cartridges, wipe away the first drop of blood as
it may contain excess tissue fluid, which can increase potassium results, and
decrease the other test results.
Air
Avoid drawing air into the capillary tube.
Blood Gas Analysis There are conflicting reports in the literature regarding the validity of PO
2
analysis performed on arterialized skin puncture specimens compared to
arterial PO
2
. The process of capillary collection may change PO
2
, PCO
2
, and
the calculated sO
2
. Arterial specimens are preferred for blood gas analysis.
See CLSI documents H4-A5, C-46A, and H11-A4 listed in the References
section for further discussion.
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