Kidney Week

Abstract: SA-OR45

The ΔAG/ΔHCO3 Ratio in Lactic Acidosis: Time for a New Baseline?

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Clinical Research
  November 04, 2023 | Location: Room 111, Pennsylvania Convention Center
  Abstract Time: 05:33 PM - 05:42 PM

Category: Fluid, Electrolytes, and Acid-Base Disorders

• 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

• Lu, Deborah Dee, Department of Nephrology and Hypertension, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California, United States

Deborah Dee Lu, MD

• Treger, Richard M., Department of Nephrology and Hypertension, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California, United States

Richard M. Treger,

• Song, Hubert, Kaiser Permanente Department of Research and Evaluation, Pasadena, California, United States

Hubert Song,

Background

The ratio of Δanion gap and Δbicarbonate (ΔAG/ΔHCO₃) is used to detect co-existing acid-base disorders in patients with high anion gap (AG) metabolic acidosis. Prior studies demonstrating that in lactic acidosis (LA) the ΔAG/ΔHCO₃ is approximately 1.6-1.8:1 used mean normal values for anion gap and serum HCO₃. This study is the first to examine the ΔAG/ΔHCO₃ using each patient’s individual baseline AG and serum HCO₃.

Methods

This was a retrospective cohort study of adult Kaiser Permanente Southern California (KPSC) health system members admitted to the ICU with sepsis. Baseline AG and albumin measurements were obtained 1-24 months prior to ICU admission. An albumin-corrected ΔAG/ΔHCO₃ ratio was calculated using each patient’s individual baseline AG and serum HCO₃. The association between ΔHCO3 and ΔAG was examined using Pearson correlation, a linear regression model was constructed, and 95% prediction limits were computed.

Results

293 patients were included. ΔAG/ΔHCO₃ was calculated for 177 patients who had elevated serum lactate levels (>1.9 mM). The mean ΔAG/ΔHCO₃ for all patients with elevated serum lactate levels was 1.44 (SD 1.89). The correlation between ΔHCO₃ and ΔAG with 95% prediction limits is shown in Figure 1.

Conclusion

The mean ΔAG/ΔHCO₃ was 1.44. To our knowledge, this is the first study to determine the ΔAG/ΔHCO₃ using each patient’s individual baseline AG and serum HCO₃. This has important clinical implications given the wide interindividual variability in AG and HCO₃. Regardless, even using the baseline AG and serum HCO₃ to calculate the ΔAG/ΔHCO₃, the wide 95% prediction limits (Figure 1) suggest that ΔAG/ΔHCO₃ should be used cautiously in the diagnosis of mixed acid-base disorders.

Figure 1: Correlation between ΔHCO₃ and ΔAG

Funding

• Commercial Support – The research is supported by a grant from the Regional Research Committee of Kaiser Permanente. Grant No. KP-RRC-20210504.