Arterial versus venous electrolytes analysis in critically ill patients: A cross-sectional observational study
R. K. Anjitha, Manisha B. Vyas, Lavanya Subbaroyan Vijayakumar, Gayatri R. NairObjectives:
The primary objective of this study was to compare electrolytes and bicarbonate values obtained from arterial and venous blood samples in the same critically ill patients presenting to the emergency department (ED). The study also aimed at comparison of the turnaround time of point-of-care and laboratory auto-analyzer reports, aiding in early diagnosis and intervention.
Materials and Methods:
This was a cross-sectional observational study conducted in 100 critically ill patients presenting to the ED. From each patient meeting the inclusion criteria, both arterial and venous samples were collected simultaneously after ensuring quality control.
Statistical analysis:
Data analysis was done using Bland-Altman analysis, and plots were used to evaluate and visualize the degree of agreement between arterial and venous sodium, potassium, chloride, and bicarbonate.
Results:
The Bland–Altman plots demonstrated clinically acceptable agreement for sodium and bicarbonate, while chloride and potassium exhibited slightly higher variability. The negative bias (mean difference -0.36 mmol/L) in potassium indicates systematically higher venous levels. The intraclass correlation coefficient (ICC) analysis showed that ABG measurements are more consistent for sodium (ICC = 0.80, 95% confidence interval [CI] 0.70–0.87) and bicarbonate (ICC = 0.81, 95% CI 0.73–0.87), compared to chloride (ICC = 0.64, 95% CI 0.51–0.75). The mean turnaround time for ABG analysis was less compared to that of the central laboratory auto-analyzer (10 ± 2.5 min; 60 ± 12 min), making ABG a better point of care for electrolytes and bicarbonate analysis.
Conclusions:
This study showed that ABG, a point-of-care test with a shorter turnaround time when compared to an autoanalyzer, is helpful in providing rapid assessment of sodium and bicarbonate in the ED, while caution is needed for interpreting potassium and chloride.