11
Capillary tube samples – preanalytical errors, continued
Sample collection and handling
5. Sample should be free of air bubbles
• Air bubbles can affect O
2
and CO
2
values
• Ensure the end caps match the type of capillary tube
• Cap both ends of the sample to avoid contact with room air
6. Mixing
• Mix GENTLY with the mixing wire and magnet to avoid hemolysis
of the sample
• Hemolysis may cause K
+
↑, Na
+
↓ and Ca
2+
↓
• Mix 20 times along the full length of the capillary tube or mix
manually by inverting the capillary tube 20 times
7. Analyze quickly
• If not analyzed quickly, the sample will continue to metabolize, causing
the following:
pO
2
↓ since O
2
will still be consumed
pCO
2
↑ since CO
2
will still be produced
pH ↓ due to change in CO
2
cCa
2+
↑ the change in pH will influence the binding of Ca
2+
to protein
cGlu ↓ since glucose will be metabolized
cLac ↑ due to metabolism
If not analyzed <30 minutes, store plastic capillary tubes at room temperature. Glass capillary tubes
can be stored in ice slurry.
11 of 36EXT-VEND-MAN-0023-1 Owner:Julie Monnox Approved:27 Mar 2019
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