6
Syringe samples – preanalytical errors, continued
Sample collection and handling
5. Visually inspect sampler and expel all air bubbles
• Air bubbles can affect O
2
and CO
2
values
safe
PICO syringes: Expel air bubbles through the vented
safe
TIPCAP
• Cap syringe to avoid contact with room air
6. Manual mixing or mixing using the integrated
mixing device
Stress that mixing makes the sample more homogeneous:
• Mixing reduces sedimentation
• Hemolysis may cause K
+
↑,
Na
+
↓
and Ca
2+
↓
• When mixing manually, invert the syringe according to local guidelines
• Discuss how to mix a sedimented sample, follow local guidelines.
• There is no real consensus as to how to invert a syringe –
an easy way to mix manually is by rolling the syringe between
your palms
• Stress that the integrated sample mixer is for
safe
PICO
syringes only
4. Correct volume of blood
• Too much blood = increased risk of clotting
• Too little blood = possible heparin binding effect
(may cause lower Ca
2+
value)
• Flush solutions used in A-lines must be removed from the
sample site to avoid dilution of blood samples
• It is recommended to withdraw a volume equal to three to
six times the “dead space” of the catheter system (CLSI)
Be aware of possible mixtures of venous and arterial blood: If
a self-filling syringe does not fill quickly, it may be because the
needle punctured the back of the arterial wall and continued
into a vein (with a lower pressure). In that case, a new sample
should be taken.
7. Analyze quickly
• If not analyzed quickly, the sample will continue to metabolize, causing the following:
p
O
2
↓
since O
2
will still be consumed
p
CO
2
↑
since CO
2
will still be produced
pH
↓
due to change in CO
2
c
Ca
2+
↑
the change in pH will influence the binding of Ca
2+
to protein
c
Glu
↓
since glucose will be metabolized
c
Lac
↑
due to metabolism
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EXT-VEND-MAN-0023-1 Owner:Julie Monnox Approved:27 Mar 2019
