Abstract
Introduction The determination of the electrolytes sodium and potassium is essential in critical care. In daily clinical practice, both the blood gas analyzer (ABG) and the laboratory autoanalyzer (AA) are generally applied. However, there is still uncertainty regarding the convergence of the prementioned assays, and data about the comparability dependent on the pH value are still lacking. Materials and Methods One hundred samples from intensive care unit patients with a range in pH values between 7.20 and 7.49 were evaluated in this retrospective cohort study. All patients suffered an infarct-related cardiogenic shock and were intubated and not under therapeutical hypothermia at the time of blood collection. We used scatter plots to compare different distributions of sodium and potassium values between the methods. Comparability of the analyses was assessed using the Bland–Altmann approach, and intraclass correlations (ICC) as estimates of interrater reliability were calculated. Results The mean potassium level measured on ABG was 4.33 mmol/L (SD 0.48 mmol/L), and the value obtained using the AA was 4.40 mmol/L (SD 0.55 mmol/L). A Bland–Altman comparison for total potassium measurements revealed that the limits of agreement were small (−0.241 to 0.391 mmol/L). Total ICC displayed a very good correlation of 0.949. For sodium, we found average values of 140 mmol/L (SD 5.20 mmol/L) in the AA and 140 mmol/L (SD 5.80 mmol/L) in the ABG assessment. Contrarily, the Bland–Altman comparison for sodium displayed that the 95% limits of agreement were very wide (−5.99 to 6.59 mmol/L) for total measurements as well as in every pH subgroup. Total ICC only reached a value of 0.830. Conclusion Data from our single-center study indicate that urgent and vital decisions based on potassium measurements can be made by trusting the value obtained on the ABG machine irrespective of pH values.
Highlights
Due to their fundamental effects on cellular functioning and metabolic processes, the accurate quantification of the electrolytes sodium and potassium is essential in clinical practice and especially in intensive care unit patients [1, 2].ere are generally two approaches applied in daily use
We investigated for the first time whether sodium and potassium ion concentrations measured with the central laboratory autoanalyzer or arterial blood gas analyzer in critical illness patients differ depending on the pH value
Differences of sodium and potassium in the arterial blood gas (ABG) and AA at different pH values are summarized in Table 1. e mean potassium level measured on ABG was 4.33 mmol/L (SD 0.48 mmol/L), and the value obtained using the AA was 4.40 mmol/L (SD 0.55 mmol/L)
Summary
Due to their fundamental effects on cellular functioning and metabolic processes, the accurate quantification of the electrolytes sodium and potassium is essential in clinical practice and especially in intensive care unit patients [1, 2].ere are generally two approaches applied in daily use. Electrolytes are routinely measured from serum by central laboratory autoanalyzers (AAs); the time between the blood drawing and the achievement of results depends on various factors such as processing, transport time, and laboratory sample analysis [3]. Such delay may compromise the treatment of critically ill patients. Arterial blood gas (ABG) analyzers have a wide application in most emergency departments and intensive care units (ICUs) due to the opportunity to obtain data quickly and to respond with prompt treatment [4].
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