Correlation Between Serum and Arterial Blood Gas Bicarbonate in Patients Admitted to the Intensive Care Unit

Objective Clinicians use two modalities to determine acid-base disturbances: calculated bicarbonate on arterial blood gas (ABG) and measured bicarbonate on basic metabolic panels (BMP). The primary objective was to investigate the discrepancy between the two values for diagnosing acidemia in the intensive care unit (ICU). Our secondary objective was to discern the threshold to treat acidemia within various clinical settings.  Materials and methods We performed a multi-center study using a retrospective patient chart review consisting of ABG and BMP bicarbonate levels at various pH ranges; 584 adult patients were included in this study. SAS software (SAS Institute Inc., Cary, NC) was used for analysis. Results Strong positive correlations were found between calculated ABG and measured BMP bicarbonate, with the group of pH 6.9-7.0 being the strongest. Based on odds ratio analysis, patients were more likely to not receive bicarbonate treatment if pH was greater than 7.1 based on calculated ABG bicarbonate. Patients also did not receive bicarbonate treatment when pH was greater than 7.2 based on BMP bicarbonate levels. Our study found that patients with higher pH (pH > 7.1) were less likely to receive bicarbonate treatment. Patients with pH 6.9-7.0 were more likely to receive bicarbonate treatment. Based on receiver operator curve (ROC) model curves, neither ABG nor BMP bicarbonate values have strong accuracy for diagnosing acidemia. Conclusion We found no significant difference in CO₂ levels and ICU types regardless of if ABG or BMP was used.