Abstract: TH-PO0086
Limitations of Serum Bicarbonate as a Criterion for Metabolic Acidosis in Patients with CKD: Implications for Clinical Trials
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Clinical Research
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Sweis, Nabil William, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
- Singh, Bhupinder, University of California Irvine, Irvine, California, United States
- Turner, Stewart A., Renibus Therapeutics Inc, Southlake, Texas, United States
- Batlle, Daniel, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
Background
Metabolic acidosis is a common acid-base disorder in chronic kidney disease (CKD) and a cause of adverse clinical outcomes. Clinical trials have shown variable effects of correction of metabolic acidosis on CKD progression. These studies relied solely on a low serum bicarbonate for the diagnosis of metabolic acidosis. We assessed acid–base status of CKD patients using venous blood pH, PCO2, and HCO3- converted to arterial blood pH, PCO2, and HCO3-.
Methods
This is an analysis of venous blood gas data of patients enrolled in the placebo-controlled TRCA-301 clinical trial evaluating the efficacy of veverimer, a hydrochloric acid-binder for metabolic acidosis in CKD. All enrolled patients (n=217) were presumed to have metabolic acidosis on the basis of a low serum bicarbonate at two screening visits (12-20 mEq/L). Using venous-to-arterial transformation formulas (Kidney360, 2026), arterial pH, PCO2, and HCO3- were estimated and then the acid-base status was categorized applying traditional criteria such as the Winter's formula.
Results
At the first screening visit, only 48% of patients, had a low estimated arterial pH (<7.35), while 52% had either a normal (7.35-7.45) or elevated (>7.45) pH. Only 19% met criteria for pure metabolic acidosis, while 59% of patients could be classified as having mixed metabolic acidosis with respiratory alkalosis. The second screening visit revealed similar findings (Fig 1). Data is presented as mean ± SD.
Conclusion
1) CKD patients diagnosed of metabolic acidosis based solely on a low serum bicarbonate often (~50%) have a normal or high pH; 2) Notwithstanding that the handling of venous blood gas samples in this study may not have been optimal in some cases, acid-base status assessed by traditional criteria reveals that a metabolic acidosis mixed with respiratory alkalosis is frequent in CKD. We suggest more rigorous phenotyping of acid–base status in patients with CKD, including information on estimated arterial pH, PCO2, and HCO3-.
Acknowledgment
Data for this analysis of venous blood gas parameters in CKD patients were made available by Renibus Therapeutics Inc, a company that acquired the rights for veverimer from Tricida Inc.
Fig 1. Analysis of estimated arterial pH (epH), PCO2 (ePCO2), and HCO3- (eHCO3-) in TRCA-301 trial at two screening visits.