title: Dialysate partitioning in the Genius batch hemodialysis system: effect of temperature and solute concentration.
abstract: BACKGROUND
  The Genius batch system contains a 75-L closed reservoir from which fresh dialysate is extracted at the top, and to which spent dialysate is returned at the bottom. In vivo studies have demonstrated that almost the entire amount of dialysate can be used before contamination of fresh with spent dialysate occurs. The question is raised whether density differences cause this separation, and what the relative contributions of temperature and solute content are.
  
  
  METHODS
  As patient substitute, a container filled with dialysate was loaded with various amounts of urea. Temperature differences between spent and fresh dialysate were imposed by not heating the dialysate at the outlet line from the dialyzer (A), heating the outlet to obtain continuously equal temperatures at inlet and outlet (B), or to temperatures as in vivo (C). With a dialysate flow set at 300 mL/min, urea is not expected at the inlet before 250 minutes.
  
  
  RESULTS
  With a urea concentration of 33 mg/dL, urea contamination at the dialysate inlet line occurred after 185 +/- 20 (A), 122 +/- 11 (B), and 175 +/- 12 minutes (C) of dialysis, whereas with 67 mg/dL, this happened at 219 +/- 5 (A), 162 +/- 11 (B), and 202 +/- 8 minutes (C). With 100 and 150 mg/dL, urea contamination appeared at 224 +/- 2 (A) and 204 +/- 14 minutes (B), and 227 +/- 5 (A) and 232 +/- 3 minutes (B), respectively.
  
  
  CONCLUSIONS
  Both temperature differences between spent and fresh dialysate and solute content of spent dialysate contribute to dialysate partitioning in the Genius dialysis system.
authors.affiliation: Renal Division, Department of Internal Medicine, Ghent University Hospital, Ghent, Belgium. annemieke.dhondt@ugent.be
authors.forename: Annemieke
authors.initials: A
authors.lastname: Dhondt
authors.forename: Sunny
authors.initials: S
authors.lastname: Eloot
authors.forename: Dirk De
authors.initials: DD
authors.lastname: Wachter
authors.forename: Rita De
authors.initials: RD
authors.lastname: Smet
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Waterloos
authors.forename: Griet
authors.initials: G
authors.lastname: Glorieux
authors.forename: Norbert
authors.initials: N
authors.lastname: Lameire
authors.forename: Pascal
authors.initials: P
authors.lastname: Verdonck
authors.forename: Raymond
authors.initials: R
authors.lastname: Vanholder
mesh_terms: D015314:Dialysis Solutions / Q000378:metabolism*; D006801:Humans; D006435:Renal Dialysis / Q000295:instrumentation*; D013696:Temperature; D014508:Urea / Q000378:metabolism
chemical_list: D015314:Dialysis Solutions; D014508:Urea