Stability of arterial blood gas samples after delayed analysis and mechanical stress.

PURPOSE: To investigate the effect of prolonged time before analysis and mechanical manipulation on pre-analytical stability of biomarkers and the validity of blood gas analysis results.

METHODS

We collected blood samples from 240 ICU patients from May 18, 2022 to March 31, 2023. Samples were analyzed immediately per standard operating procedure, then the syringes were kept at room temperature for 60 min, subjected to standardized mechanical forces (repeated drops) and analyzed again. Thirteen typical blood gas analytes were measured. Bland-Altman plots were prepared to assess differences between initial and delayed analyses. Differences were compared against official accuracy limits specified in German quality assurance guidelines (Rili-BAEK).

RESULTS

For hemoglobin, creatinine, glucose, and electrolytes (calcium, sodium, chloride, bicarbonate), agreement between immediate and post-delay analyses remained within the official acceptable ranges. For pH and potassium, deviations exceeded the Rili-BAEK accuracy limits but remained clinically acceptable. Only oxygen partial pressure and lactate levels changed so markedly that they would no longer be reliable for clinical interpretation.

CONCLUSION

Even after a 60-min delay and excessive mechanical stress, selected blood gas analytes such as hemoglobin, glucose, and electrolytes can be considered valid. Potassium and carbon dioxide partial pressure were altered but might be suitable for approximation purposes. Findings for oxygen partial pressure and lactate were generally invalid. In the future, these findings can aid in reducing unnecessary blood sampling. These findings may guide clinicians in deciding whether repeat sampling is necessary, potentially reducing unnecessary blood draws, while reinforcing that critical parameter (pO₂, pCO₂, pH) still require prompt analysis.