• Mirela Dobre, Wei Yang, Jing Chen, Paul Drawz, L Lee Hamm, Edward Horwitz, Thomas Hostetter, Bernard Jaar, Claudia M Lora, Lisa Nessel, Akinlolu Ojo, Julia Scialla, Susan Steigerwalt, Valerie Teal, Myles Wolf, Mahboob Rahman, and CRIC Investigators.
• Case Western Reserve University, Cleveland, OH; Division of Nephrology and Hypertension, University Hospital Case Medical Center, Cleveland, OH; Louis Stokes Cleveland VA Medical Center, Cleveland, OH. Electronic address: mirela.dobre@uhhospitals.org.
• Am. J. Kidney Dis. 2013 Oct 1; 62 (4): 670-8.

BackgroundThe purpose of this study is to evaluate serum bicarbonate level as a risk factor for renal outcomes, cardiovascular events, and mortality in patients with chronic kidney disease (CKD).Study DesignObservational cohort study.Setting & Participants3,939 participants with CKD stages 2-4 who enrolled in the Chronic Renal Insufficiency Cohort (CRIC) between June 2003 and December 2008.PredictorSerum bicarbonate level.OutcomesRenal outcomes, defined as end-stage renal disease (either initiation of dialysis therapy or kidney transplantation) or 50% reduction in estimated glomerular filtration rate (eGFR); atherosclerotic events (myocardial infarction, stroke, or peripheral arterial disease); congestive heart failure events; and death.MeasurementsTime to event.ResultsMean eGFR was 44.8 ± 16.8 (SD) mL/min/1.73 m(2), and median serum bicarbonate level was 24 (IQR, 22-26) mEq/L. During a median follow-up of 3.9 years, 374 participants died, 767 had a renal outcome, 332 experienced an atherosclerotic event, and 391 had a congestive heart failure event. In adjusted analyses, the risk of developing a renal end point was 3% lower per 1-mEq/L increase in serum bicarbonate level (HR, 0.97; 95% CI, 0.94-0.99; P = 0.01). The association was stronger for participants with eGFR >45 mL/min/1.73 m(2) (HR, 0.91; 95% CI, 0.85-0.97; P = 0.004). The risk of heart failure increased by 14% (HR, 1.14; 95% CI, 1.03-1.26; P = 0.02) per 1-mEq/L increase in serum bicarbonate level over 24 mEq/L. Serum bicarbonate level was not associated independently with atherosclerotic events (HR, 0.99; 95% CI, 0.95-1.03; P = 0.6) and all-cause mortality (HR, 0.98; 95% CI, 0.95-1.02; P = 0.3).LimitationsSingle measurement of sodium bicarbonate.ConclusionsIn a cohort of participants with CKD, low serum bicarbonate level was an independent risk factor for kidney disease progression, particularly for participants with preserved kidney function. The risk of heart failure was higher at the upper extreme of serum bicarbonate levels. There was no association between serum bicarbonate level and all-cause mortality or atherosclerotic events.Copyright © 2013 National Kidney Foundation, Inc. All rights reserved.

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