title: Serum bicarbonate and mortality in stage 3 and stage 4 chronic kidney disease.
abstract: OBJECTIVE
  The incidence and prevalence of metabolic acidosis increase with declining kidney function. We studied the associations of both low and high serum bicarbonate levels with all-cause mortality among stage 3 and 4 chronic kidney disease (CKD) patients.
  
  
  METHODS
  We examined factors associated with low (<23 mmol/L) and high (>32 mmol/L) serum bicarbonate levels using logistic regression models and associations between bicarbonate and all-cause mortality using Cox-proportional hazard models, Kaplan-Meier survival curves, and time-dependent analysis.
  
  
  RESULTS
  Out of 41,749 patients, 13.9% (n = 5796) had low and 1.6% (n = 652) had high serum bicarbonate levels. After adjusting for relevant covariates, there was a significant association between low serum bicarbonate and all-cause mortality (hazard ratio [HR] 1.23, 95% CI 1.16, 1.31). This association was not statistically significant among patients with stage 4 CKD and diabetes. The time-dependent analysis demonstrated a significant mortality risk associated with a decline from normal to low bicarbonate level (HR 1.59, 95% CI 1.49, 1.69). High serum bicarbonate levels were associated with death irrespective of the level of kidney function (HR 1.74, 95% CI 1.52, 2.00). When serum bicarbonate was examined as a continuous variable, a J-shaped relationship was noted between serum bicarbonate and mortality.
  
  
  CONCLUSIONS
  Low serum bicarbonate levels are associated with increased mortality among stage 3 CKD patients and patients without diabetes. High serum bicarbonate levels are associated with mortality in both stage 3 and stage 4 CKD patients.
authors: Department of Nephrology, Hypertension, Glickman Urological and Kidney Institute, and Cleveland Clinic Lerner College of Medicine of CWRU, Cleveland, OH 44195, USA. navanes@ccf.org
authors: Sankar D
authors: SD
authors: Navaneethan
authors: Jesse D
authors: JD
authors: Schold
authors: Susana
authors: S
authors: Arrigain
authors: Stacey E
authors: SE
authors: Jolly
authors: Edgard
authors: E
authors: Wehbe
authors: Rupesh
authors: R
authors: Raina
authors: James F
authors: JF
authors: Simon
authors: Titte R
authors: TR
authors: Srinivas
authors: Anil
authors: A
authors: Jain
authors: Martin J
authors: MJ
authors: Schreiber
authors: Joseph V
authors: JV
authors: Nally
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001639:Bicarbonates / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D016009:Chi-Square Distribution; D002908:Chronic Disease; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D007674:Kidney Diseases / Q000097:blood* / Q000401:mortality*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009820:Ohio; D016016:Proportional Hazards Models; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors
chemical_list: D001639:Bicarbonates; D015415:Biomarkers