title: Ultrafiltration Rate and Mortality in Maintenance Hemodialysis Patients.
abstract: BACKGROUND
  Observational data have demonstrated an association between higher ultrafiltration rates and greater mortality among hemodialysis patients. Prior studies were small and did not consider potential differences in the association across body sizes and other related subgroups. No study has investigated ultrafiltration rates normalized to anthropometric measures beyond body weight. Also, potential methodological shortcomings in prior studies have led to questions about the veracity of the ultrafiltration rate-mortality association.
  
  
  METHODS
  Retrospective cohort.
  
  
  METHODS
  118,394 hemodialysis patients dialyzing in a large dialysis organization, 2008 to 2012.
  
  
  METHODS
  Mean 30-day ultrafiltration rates were dichotomized at 13 and 10mL/h/kg, separately and categorized using various cutoff points. Ultrafiltration rates normalized to body weight, body mass index, and body surface area were investigated.
  
  
  RESULTS
  All-cause mortality.
  
  
  METHODS
  Multivariable survival models were used to estimate the association between ultrafiltration rate and all-cause mortality.
  
  
  RESULTS
  At baseline, 21,735 (18.4%) individuals had ultrafiltration rates > 13mL/h/kg and 48,529 (41.0%) had ultrafiltration rates > 10mL/h/kg. Median follow-up was 2.3 years, and the mortality rate was 15.3 deaths/100 patient-years. Compared with ultrafiltration rates ≤ 13mL/h/kg, ultrafiltration rates > 13mL/h/kg were associated with greater mortality (adjusted HR, 1.31; 95% CI, 1.28-1.34). Compared with ultrafiltration rates ≤ 10mL/h/kg, ultrafiltration rates > 10mL/h/kg were associated with greater mortality (adjusted HR, 1.22; 95% CI, 1.20-1.24). Findings were consistent across subgroups of sex, race, dialysis vintage, session duration, and body size. Higher ultrafiltration rates were associated with greater mortality when normalized to body weight, body mass index, and body surface area.
  
  
  CONCLUSIONS
  Residual confounding cannot be excluded given the observational study design.
  
  
  CONCLUSIONS
  Regardless of the threshold implemented, higher ultrafiltration rate was associated with greater mortality in the overall study population and across key subgroups. Randomized controlled trials are needed to investigate whether ultrafiltration rate reduction improves clinical outcomes.
authors: University of North Carolina Kidney Center, Division of Nephrology and Hypertension, Department of Medicine, UNC School of Medicine, Chapel Hill, NC; Department of Epidemiology, UNC Gillings School of Global Public Health, Chapel Hill, NC.
authors: Magdalene M
authors: MM
authors: Assimon
authors: University of North Carolina Kidney Center, Division of Nephrology and Hypertension, Department of Medicine, UNC School of Medicine, Chapel Hill, NC.
authors: Julia B
authors: JB
authors: Wenger
authors: Department of Epidemiology, UNC Gillings School of Global Public Health, Chapel Hill, NC; Cecil G. Sheps Center for Health Services Research, University of North Carolina, Chapel Hill, NC.
authors: Lily
authors: L
authors: Wang
authors: University of North Carolina Kidney Center, Division of Nephrology and Hypertension, Department of Medicine, UNC School of Medicine, Chapel Hill, NC; Cecil G. Sheps Center for Health Services Research, University of North Carolina, Chapel Hill, NC. Electronic address: jflythe@med.unc.edu.
authors: Jennifer E
authors: JE
authors: Flythe
mesh_terms: D001837:Body Weights and Measures; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000379:methods / Q000401:mortality*; D012189:Retrospective Studies; D014462:Ultrafiltration / Q000706:statistics & numerical data
keywords: Hemodialysis; anthropometric measures; body mass index (BMI); body size; body surface area (BSA); body weight; end-stage renal disease (ESRD); metabolic mass; mortality; rapid fluid removal; ultrafiltration rate (UFR)