Effects of collecting blood into plastic heparinised vacutainer tubes and storage conditions on blood gas analysis values in horses.
BACKGROUND
Plastic heparinised vacutainer tubes are used for blood gas analysis in horses. This collection method may not be ideal because influx of atmospheric O(2) through the permeable plastic wall of the vacutainer tube and loss of CO(2) into the gas phase above the blood sample should increase blood PO(2) and decrease PCO(2), respectively.


OBJECTIVE
To determine the effects of collecting blood into plastic vacutainer tubes and storage conditions on blood gas analysis values.


METHODS
Blood was obtained from 6 healthy horses and tonometered at 37 °C with 12% O(2) and 5% CO(2). Three ml aliquots of tonometered blood were collected using a glass syringe or vacutainer tube and stored in iced water or at room temperature for 0, 5, 15, 30, 60 and 120 min. Blood samples from vacutainer tubes were collected aerobically (tube opened for 5 s) or anaerobically (tube remained closed). Blood gas analysis was performed in duplicate using a Radiometer ABL5. Data was analysed using repeated measures analysis of variance and P < 0.05 was significant.


RESULTS
Compared to the glass syringe, tonometered blood collected in vacutainer tubes had an immediate, significant, sustained and marked increase in PO(2) and an immediate, significant, transient but small decrease in PCO(2). Blood PO(2) and PCO(2) were higher when vacutainer tubes were stored in iced water instead of at room temperature. Measured blood pH and calculated values for plasma bicarbonate and total CO(2) concentration and base excess of extracellular fluid were similar when blood was collected in glass syringes or vacutainer tubes and values were not altered by storage temperature or time.


CONCLUSIONS
Plastic heparinised vacutainer tubes should not be used to collect samples for measurement of blood PCO(2) and PO(2). Vacutainer tubes provide an accurate method for measuring plasma bicarbonate concentration, total CO(2) concentration and base excess.
Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA.
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Noël
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Couëtil
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D000818:Animals; D001639:Bicarbonates / Q000097:blood; D001784:Blood Gas Analysis / Q000662:veterinary*; D001800:Blood Specimen Collection / Q000295:instrumentation / Q000662:veterinary*; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D006736:Horses / Q000097:blood*; D006863:Hydrogen-Ion Concentration; D008297:Male; D010100:Oxygen / Q000097:blood; D013048:Specimen Handling / Q000379:methods / Q000662:veterinary*
D001639:Bicarbonates; D002245:Carbon Dioxide; D010100:Oxygen