Effects of Analysis Delay on pH, pO₂, pCO₂, Bicarbonate, Glucose, Lactate, Electrolytes, and Other Arterial Blood Gas...

One of the preanalytical factors that can affect the results of arterial blood gas (ABG) analysis is the time from sample collection to analysis. A delay in analysis may affect the results due to factors such as ongoing cellular metabolism within the blood sample, gas exchange between the blood sample and the environment, and temperature changes. ABG analysis can be delayed for various reasons, for instance, due to long transport distances between the collection site and the analyzer. The aim of this study was to describe the changes that occur in ABG samples over time and identify the time point at which the first variable exceeded a predefined clinically acceptable threshold.

The final analysis included samples from a total of 80 patients. Two ABG samples from each patient were analyzed simultaneously on two types of blood gas analyzers at 0, 5, 10, 20, 30, 45, 60, and 120 min.

The first variable change that reached the predetermined level of clinical relevance was the oxygen partial pressure (pO₂), which had increased above this level after 45 min on both blood gas analyzers. At 30 min, all variable changes remained within the predetermined range for clinical relevance.

Although it is best practice to perform ABG analysis as soon as possible after sample collection, analysis may be unavoidably delayed. According to our results, changes in the blood gas variables did not exceed the predefined thresholds for clinical relevance during the first 30 min after sample collection.