title: Association of dialysate bicarbonate concentration with mortality in the Dialysis Outcomes and Practice Patterns Study (DOPPS).
abstract: BACKGROUND
  Most hemodialysis patients worldwide are treated with bicarbonate dialysis using sodium bicarbonate as the base. Few studies have assessed outcomes of patients treated with different dialysate bicarbonate levels, and the optimal concentration remains uncertain.
  
  
  METHODS
  The Dialysis Outcomes and Practice Patterns Study (DOPPS) is an international prospective cohort study.
  
  
  METHODS
  This study included 17,031 patients receiving thrice-weekly in-center hemodialysis from 11 DOPPS countries (2002-2011).
  
  
  METHODS
  Dialysate bicarbonate concentration.
  
  
  RESULTS
  All-cause and cause-specific mortality and first hospitalization, using Cox regression to estimate the effects of dialysate bicarbonate concentration, adjusting for potential confounders.
  
  
  METHODS
  Demographics, comorbid conditions, laboratory values, and prescriptions were abstracted from medical records.
  
  
  RESULTS
  Mean dialysate bicarbonate concentration was 35.5 ± 2.7 (SD) mEq/L, ranging from 32.2 ± 2.3 mEq/L in Germany to 37.0 ± 2.6 mEq/L in the United States. Prescription of high dialysate bicarbonate concentration (≥38 mEq/L) was most common in the United States (45% of patients). Approximately 50% of DOPPS facilities used a single dialysate bicarbonate concentration. 3,913 patients (23%) died during follow-up. Dialysate bicarbonate concentration was associated positively with mortality (adjusted HR, 1.08 per 4 mEq/L higher [95% CI, 1.01-1.15]; HR for dialysate bicarbonate ≥38 vs 33-37 mEq/L, 1.07 [95% CI, 0.97-1.19]). Results were consistent across levels of pre-dialysis session serum bicarbonate and between facilities that used a single dialysate bicarbonate concentration and those that prescribed different concentrations to individual patients. The association of dialysis bicarbonate concentration with mortality was stronger in patients with longer dialysis vintage.
  
  
  CONCLUSIONS
  Due to the observational nature of the present study, we cannot rule out that the reported associations may be biased by unmeasured confounders.
  
  
  CONCLUSIONS
  High dialysate bicarbonate concentrations, especially prolonged exposure, may contribute to adverse outcomes, likely through the development of postdialysis metabolic alkalosis. Additional studies are warranted to identify the optimal dialysate bicarbonate concentration.
authors.affiliation: Arbor Research Collaborative for Health, Ann Arbor, MI; Vanderbilt University Medical Center, Nashville, TN. Electronic address: francesca.tentori@arborresearch.org.
authors.forename: Francesca
authors.initials: F
authors.lastname: Tentori
authors.forename: Angelo
authors.initials: A
authors.lastname: Karaboyas
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Robinson
authors.forename: Hal
authors.initials: H
authors.lastname: Morgenstern
authors.forename: Jinyao
authors.initials: J
authors.lastname: Zhang
authors.forename: Ananda
authors.initials: A
authors.lastname: Sen
authors.forename: T Alp
authors.initials: TA
authors.lastname: Ikizler
authors.forename: Hugh
authors.initials: H
authors.lastname: Rayner
authors.forename: Rachel B
authors.initials: RB
authors.lastname: Fissell
authors.forename: Raymond
authors.initials: R
authors.lastname: Vanholder
authors.forename: Tadashi
authors.initials: T
authors.lastname: Tomo
authors.forename: Friedrich K
authors.initials: FK
authors.lastname: Port
mesh_terms: D000368:Aged; D001639:Bicarbonates / Q000032:analysis*; D015331:Cohort Studies; D015314:Dialysis Solutions / Q000737:chemistry*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D006435:Renal Dialysis / Q000401:mortality*
chemical_list: D001639:Bicarbonates; D015314:Dialysis Solutions
keywords: Dialysis Outcomes and Practice Patterns Study (DOPPS); Hemodialysis; observational; outcomes; statistics