Defining blood gas analysis stability limits across five sample types

Accurate reporting of blood gas samples is dependent upon following proper preanalytical sample handling requirements though there is variation for sample acceptability criteria across institutions. We examined five common sample types (arterial, venous, umbilical arterial, umbilical venous and capillary) stored at either room temperature or on crushed ice in a time series (0, 15, 30, 45, 60, 90, 180, 240 min) and applied local regulatory and/or institutional allowable performance limits to determine the need for cold preservation and/or maximum stability time for pH, pO₂, pCO₂, glucose, lactate, sodium, potassium, chloride, and ionized calcium where applicable in each sample type. Although changes in sample pO₂ and/or lactate values were responsible, in part or in whole, for surpassing the allowable limits in nearly all sample types analyzed, this was not uniformly observed across sample types within the typical time limits that are referenced in literature. Furthermore, we demonstrated that cold preservation may not ubiquitously provide longer stability for blood gas specimens and this is dependent on the sample type and analyte in question. Nevertheless, these results demonstrate the known instability of pO₂ and lactate and suggest that it may be possible to simplify the monitoring of preanalytical conditions by first evaluating pO₂ and lactate in patient blood gas samples if applicable.