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Abstract: FR-PO566

Unmeasured Organic Anions as Predictors of Clinical Outcomes in Lactic Acidosis due to Sepsis

Session Information

Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders

  • 1002 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Clinical


  • Treger, Richard M., Kaiser Foundation Hospitals, Pasadena, California, United States
  • Zaki, Kirollos Emad, Kaiser Foundation Hospitals, Pasadena, California, United States
  • Asef, Mark, Kaiser Foundation Hospitals, Pasadena, California, United States

In lactic acidosis, lactate can only explain 25% of the variance in the anion gap (AG). Our recent work has shown that the elevated AG not explained by lactate is due to unmeasured organic anions (UOA). Small studies suggested that UOA may better predict clinical outcomes than lactate. The aim of this study was to determine whether UOA predict clinical outcomes better than lactate levels.


This was a retrospective cohort study of adult ICU patients with sepsis. A baseline period beginning 1 year prior was used to obtain baseline AG and albumin measurements. An albumin-corrected delta AG was calculated. UOA were estimated using the formula: Delta AG – serum lactate. A logistic regression model was constructed to explore the relationship between in-hospital mortality, UOA and lactate.


526 patients were included (Table). In the adjusted model examining lactate and UOA, the OR [95% CI] for predicting in-hospital mortality was 1.18 [1.03-1.34] and 0.97 [0.89-1.04], respectively.


Lactate was associated with higher in-hospital mortality. However, UOA were not associated with increased risk of in-hospital mortality. This disproved our hypothesis that UOA would predict in-hospital mortality better than lactate suggested by previous small studies. However, these studies used strong ion gap to estimate UOA while our study used a more precise quantitative estimate of UOA, including use of baseline albumin-corrected AG. Prior studies attempting to identify UOA have identified Krebs cycle intermediates including citrate and isocitrate, suggesting that in our study UOA were not associated with increased in-hospital mortality because they are a marker of disrupted aerobic metabolism rather than a complete switch to anaerobic metabolism

Patient characteristics
Age (years; mean + SD)71.1 + 13.14
Male (n/N [%])268/526 (51.0)
Developed AKI (n/N [%])242/526 (46.0)
Required dialysis (n/N [%])124/526 (23.6)
Elixhauser index (mean + SD)8.9 + 3.41
SOFA score (mean + SD)5.9 + 4.08
Systolic BP (mean + SD)112.3 + 27.97
Lactate (mean + SD)3.1 + 2.68
ICU AG (mean + SD)15.7 + 4.67
Delta AG (mean + SD)4.3 + 5.11
Unmeasured organic anions (mean + SD)1.2 + 4.15


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