MGM Journal of Medical Sciences (Jul 2024)

Comparison of sodium and potassium values in arterial and venous blood samples

  • M Mikun,
  • K Sivakumar ,
  • Prabha Thangaraj,
  • R Thamarai

DOI
https://doi.org/10.4103/mgmj.mgmj_180_24
Journal volume & issue
Vol. 11, no. 3
pp. 455 – 459

Abstract

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Background: In routine practice, electrolytes are measured in serum using an electrolyte analyzer, which takes approximately 30 min. In contrast, electrolyte measurements from arterial blood using an arterial blood gas (ABG) analyzer can be completed within 5–10 min. However, limited information compares electrolyte values between venous and arterial samples. This study aims to determine if sodium (Na) and potassium (K) test results from arterial blood and venous serum samples can be used interchangeably. Materials and Methods: An observational cross-sectional study was conducted over 2 months (July and August 2019) at a tertiary care teaching hospital and research center. Data were collected from 50 intensive care unit patients, including their ABG analysis and serum electrolyte reports. The ABG samples, collected in heparinized syringes, were processed immediately using GEM Premier 3500 Blood gas analyzer. Serum electrolytes were measured with the Roche 9180 analyzer after centrifugation. Data analyses were performed using IBM Statistical Package for the Social Sciences version 21, and Bland–Altman plots were used to compare the results. Results: The mean sodium levels in venous samples and arterial blood were statistically insignificant (P < 0.17). In contrast, a significant difference was observed in potassium measurements between the two sample types (P = 0.000, null hypothesis rejected). The mean difference in sodium (Na+) results was 2.01 mEq/L, with a limit of agreement ranging from −17.98 to 22 mEq/L. The bias in arterial potassium was 0.99 mEq/L, with a 95% limit of agreement from 0.01 to 1.97 mEq/L. Conclusions: While sodium results from arterial and venous samples were similar, potassium results differed significantly. Therefore, potassium measurements from ABG and serum electrolyte analyzers should not be used interchangeably and must be interpreted cautiously.

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