Short-term effects of storage time and temperature on pH, pCO2, and pO2 in porcine arterial blood

Abstract

There is evidence that pre-analytical handling may be an important determinant of blood gas variables. To study this possibility we investigated the influence of storage time (5, 15, 30, 45, and 60 minutes after blood sampling) and storage temperature (4oC and 20oC) on the variation in pH, pCO2, and pO2 in porcine blood. We found that the median pH decreased (P<0.001), but did not exhibit clinically significant changes. The median pCO2 increased with duration of storage (P<0.001) and the median pO2 was variable at 4oC (P=0.002), and decreased at 20oC (P<0.001). The variations in pCO2 and pO2 were higher at 20oC than at 4oC. This study demonstrates that time delay before analysis of blood gas can be a cause of increased variation, and should be minimised in order to avoid false results and to ensure correct conclusions. If a delay of more than five minutes in analysis is expected, the specimen should be placed on crushed ice.