title: Impact of increasing haemodialysis frequency versus haemodialysis duration on removal of urea and guanidino compounds: a kinetic analysis.
abstract: BACKGROUND
  Patients with renal failure retain a large variety of uraemic solutes, characterized by different kinetic behaviour. It is not entirely clear what the impact is of increasing dialysis frequency and/or duration on removal efficiency, nor whether this impact is the same for all types of solutes.
  
  
  METHODS
  This study was based on two-compartmental kinetic data obtained in stable haemodialysis patients (n = 7) for urea, creatinine (CREA), guanidinosuccinic acid (GSA) and methylguanidine (MG). For each individual patient, mathematical simulations were performed for different dialysis schedules, varying in frequency, duration and intensity. For each dialysis schedule, plasmatic and extraplasmatic weekly time-averaged concentrations (TAC) were calculated, as well as their %difference to weekly TAC of the reference dialysis schedule (three times weekly 4 h).
  
  
  RESULTS
  Increasing dialysis duration was most beneficial for CREA and MG, which are distributed in a larger volume (54.0 +/- 5.9 L and 102.6 +/- 33.9 L) than urea (42.7 +/- 6.0 L) [plasmatic weekly TAC decrease of 31.5 +/- 3.2% and 31.8 +/- 3.8% for CREA and MG with Q(B) of 200 mL/min, compared to 25.7 +/- 3.2% for urea (P = 0.001 and P < 0.001)]. Increasing dialysis frequency resulted only in a limited increase in efficiency, most pronounced for solutes distributed in a small volume like GSA (30.6 +/- 4.2 L). Increasing both duration and frequency results in weekly TAC decreases of >65% for all solutes. Comparable results were found in the extraplasmatic compartment.
  
  
  CONCLUSIONS
  Prolonged dialysis significantly reduces solute concentration levels, especially for those solutes that are distributed in a larger volume. Increasing both dialysis frequency and duration is the superior dialysis schedule.
authors.affiliation: Nephrology Section, Department of Internal Medicine, Ghent University Hospital, Ghent, Belgium. sunny.eloot@ugent.be
authors.forename: Sunny
authors.initials: S
authors.lastname: Eloot
authors.forename: Wim
authors.initials: W
authors.lastname: van Biesen
authors.forename: Annemieke
authors.initials: A
authors.lastname: Dhondt
authors.forename: Rita
authors.initials: R
authors.lastname: de Smet
authors.forename: Bart
authors.initials: B
authors.lastname: Marescau
authors.forename: Peter Paul
authors.initials: PP
authors.lastname: De Deyn
authors.forename: Pascal
authors.initials: P
authors.lastname: Verdonck
authors.forename: Raymond
authors.initials: R
authors.lastname: Vanholder
mesh_terms: D006146:Guanidines / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008760:Methylguanidine / Q000378:metabolism*; D006435:Renal Dialysis / Q000706:statistics & numerical data*; D013386:Succinates / Q000378:metabolism*; D013997:Time Factors; D014508:Urea / Q000378:metabolism*
chemical_list: D006146:Guanidines; D013386:Succinates; D008760:Methylguanidine; C001318:guanidinosuccinic acid; D014508:Urea