title: Sodium setpoint and gradient in bicarbonate hemodialysis.
abstract: BACKGROUND
  The demonstration of an individual osmolar setpoint in hemodialysis (HD) is crucial to individualize dialysate sodium concentrations. Furthermore, the diffusive gradient between plasma and dialysate sodium is important in the "fine tuning" of the intradialytic sodium mass balance (MB).
  
  
  METHODS
  The design of this study included part A: a retrospective analysis of predialysis plasma sodium concentrations extracted from a 6-year database in our HD population (147 prevalent white anuric patients); and part B: study of intradialytic sodium kinetics in 48 patients undergoing one 4-hour bicarbonate HD session. Direct potentiometry with an ion-selective electrode was used for sodium measurements.
  
  
  RESULTS
  Study part A: the mean number of plasma sodium measurements per patient was 16.06 ± 14.03 over a mean follow-up of 3.55 ± 1.76 years. The mean of the averaged plasma sodium concentrations was 136.7 ± 2.1 mmol/L, with a low mean intraindividual coefficient of variation (1.39 ± 0.4). Study part B: mean predialysis and postdialysis plasma sodium concentrations were 135.8 ± 0.9 and 138.0 ± 0.9 mmol/L (p<0.001). Mean inlet dialyzer sodium concentration was 138.7 ± 1.1 mmol/L; the hourly diffusion concentration gradients showed a statistically significant transfer from dialysate to plasma (Wilks ? <0.0001). A statistically significant relationship was found between sodium MB and diffusion gradient (p<0.02), and between sodium MB and ultrafiltration volume (p<0.01).
  
  
  CONCLUSIONS
  A relatively "fixed" and individual osmolar setpoint in HD patients was shown for the first time in a long-term follow-up. A dialysate sodium concentration of 140 mmol/L determined a dialysate to plasma sodium gradient.
authors.affiliation: Nephrology and Dialysis Unit, Department of Medicine, Miulli General Hospital, Acquaviva delle Fonti - Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Basile
authors.forename: Pasquale
authors.initials: P
authors.lastname: Libutti
authors.forename: Piero
authors.initials: P
authors.lastname: Lisi
authors.forename: Luigi
authors.initials: L
authors.lastname: Vernaglione
authors.forename: Francesco
authors.initials: F
authors.lastname: Casucci
authors.forename: Nicola
authors.initials: N
authors.lastname: Losurdo
authors.forename: Annalisa
authors.initials: A
authors.lastname: Teutonico
authors.forename: Carlo
authors.initials: C
authors.lastname: Lomonte
mesh_terms: D000328:Adult; D000368:Aged; D001002:Anuria / Q000097:blood; D019540:Area Under Curve; D001639:Bicarbonates; D018481:Convection; D015314:Dialysis Solutions / Q000737:chemistry*; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D006435:Renal Dialysis; D012189:Retrospective Studies; D012964:Sodium / Q000032:analysis* / Q000097:blood; D013997:Time Factors
chemical_list: D001639:Bicarbonates; D015314:Dialysis Solutions; D012964:Sodium