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Rapidlab 1200 Operator’s Guide: Operating the System 2-9
02087462 Rev. V
Handling and Storing Samples
The following condition can cause erroneous results even when samples are
collected correctly:
•
Metabolic activity in the sample that occurs between sampling and
completion of analyses
• Contamination of the sample by room air
• Incorrect mixing of the sample before analysis
To minimize the errors these conditions can cause, use correct storage and
handling techniques. You can minimize errors caused by metabolic changes by
analyzing samples as soon as possible after collection. This is particularly
important for
p O
2
, glucose, and lactate values, because the sample consumes
oxygen and glucose, and lactate is rapidly formed during storage. Lactate is
produced by glycolysis and increases while the sample is stored. Glycolysis is
temperature dependent. Lactate increases approximately 0.1 mM/hour at 4°C and
1.0 mM/hour at 37°C.
1
The rate of oxygen consumption depends on several
factors:
•
Storage temperature
• White blood cell count
• Reticulocyte count
Observe the following sample-handling and storage steps when you obtain human
whole blood samples:
2
• Analyze the sample as soon as possible to minimize oxygen consumption.
• Blood collected for special studies, such as A-a O
2
gradients, or shunt studies,
should be analyzed within 5 minutes of collection.
• Plastic syringes should not be iced, but kept at room temperature as long as
the blood is analyzed within 30 minutes of collection.
• Oxygen and carbon diaoxide levels in blood kept at room temperature for
30 minutes or less are minimally affected except in the presence of an
elevated leukocyte or platelet count.
• If a prolonged time delay of more than 30 minutes before analysis is
anticipated, the use of glass syringes and storage in ice water are
recommended.
Syringes stored in ice water should not be used for electrolyte determinations
as room temperature effects on diffusion in and out of the red blood cells can
cause unreliable potassium results. Store in ice water is applicable to blood
gas measurements.
1 Wandrup, Clinical Chemistry, 35/8, 1741, (1989)
2 Blood Gas and pH analysis and Related Measurements: Approved Guideline; CLSI Document C46-A;
(Vol. 21, No. 14); 2001.