Nicholas M Mohr1, J Priyanka Vakkalanka2, Brett A Faine3, Brian Skow4, Karisa K Harland5, Ryan Dick-Perez6, Brian M Fuller7, Azeemuddin Ahmed5, Steven Q Simson8. 1. Department of Emergency Medicine, University of Iowa College of Medicine, Iowa City, IA, United States; Division of Critical Care, Department of Anesthesia, University of Iowa Carver College of Medicine, Iowa City, IA, United States. Electronic address: nicholas-mohr@uiowa.edu. 2. Department of Emergency Medicine, University of Iowa College of Medicine, Iowa City, IA, United States; Department of Epidemiology, University of Iowa College of Public Health, Iowa City, IA, United States. 3. Department of Emergency Medicine, University of Iowa College of Medicine, Iowa City, IA, United States; University of Iowa College of Pharmacy, Iowa City, IA, United States. 4. Avera eCARE, Sioux Falls, SD, United States. 5. Department of Emergency Medicine, University of Iowa College of Medicine, Iowa City, IA, United States. 6. Division of Critical Care, Department of Anesthesia, University of Iowa Carver College of Medicine, Iowa City, IA, United States. 7. Departments of Emergency Medicine and Anesthesiology, Division of Critical Care, Washington University School of Medicine, St. Louis, MO, United States. 8. Division of Pulmonary Disease and Critical Care Medicine, University of Kansas Medical Center, Kansas City, KS, United States.
Abstract
PURPOSE: (1) To test whether serum bicarbonate or anion gap can be used to predict elevated lactate or mortality in emergency department (ED) patients with sepsis, and (2) to define thresholds that may predict elevated lactate and mortality. METHODS: Retrospective diagnostic-validation study of adults with sepsis treated in a 60,000-visit Midwestern university ED (2010-2015). In the derivation sample, 8 experts selected thresholds based on objective measures to optimize clinical utility. Test performance was reported using likelihood ratios (LR +/-) in the validation cohort. RESULTS: We included 4159 patients. Anion gap predicted lactate>2 better than bicarbonate [ROC AUC 0.680 vs. 0.609], and anion gap predicted lactate>4 better than lactate>2 [ROC AUC 0.816 vs. 0.680]. In the validation cohort, anion gap ≥20mEq/L had LR+ for lactate>2 of 3.670 (2.630-5.122), lactate>4 of 7.019 (5.310-9.278), and mortality of 2.768 (1.922-3.986). Anion gap predicted mortality similar to lactate>2 [LR+ 2.768 vs. LR+ 2.09; LR- 0.823 vs. 0.447]. CONCLUSIONS: Anion gap and serum bicarbonate poorly predict changes in lactate and mortality. In resource-limited settings where lactate is unavailable, anion gap ≥20mEq/L may be used to further risk-stratify patients for ongoing sepsis care, but lactate remains a preferred biomarker.
PURPOSE: (1) To test whether serum bicarbonate or anion gap can be used to predict elevated lactate or mortality in emergency department (ED) patients with sepsis, and (2) to define thresholds that may predict elevated lactate and mortality. METHODS: Retrospective diagnostic-validation study of adults with sepsis treated in a 60,000-visit Midwestern university ED (2010-2015). In the derivation sample, 8 experts selected thresholds based on objective measures to optimize clinical utility. Test performance was reported using likelihood ratios (LR +/-) in the validation cohort. RESULTS: We included 4159 patients. Anion gap predicted lactate>2 better than bicarbonate [ROC AUC 0.680 vs. 0.609], and anion gap predicted lactate>4 better than lactate>2 [ROC AUC 0.816 vs. 0.680]. In the validation cohort, anion gap ≥20mEq/L had LR+ for lactate>2 of 3.670 (2.630-5.122), lactate>4 of 7.019 (5.310-9.278), and mortality of 2.768 (1.922-3.986). Anion gap predicted mortality similar to lactate>2 [LR+ 2.768 vs. LR+ 2.09; LR- 0.823 vs. 0.447]. CONCLUSIONS: Anion gap and serum bicarbonate poorly predict changes in lactate and mortality. In resource-limited settings where lactate is unavailable, anion gap ≥20mEq/L may be used to further risk-stratify patients for ongoing sepsis care, but lactate remains a preferred biomarker.