title: A reliable method to assess the water permeability of a dialysis system: the global ultrafiltration coefficient.
abstract: Recent randomized controlled trials suggest that sufficiently high convection post-dilutional haemodiafiltration (HC-HDF) improves survival in dialysis patients, consequently this technique is increasingly being adopted. However, when performing HC-HDF, rigorous control systems of the ultrafiltration setting are required. Assessing the global ultrafiltration coefficient of the dialysis system [GKD-UF; defined as ultrafiltration rate (QUF)/transmembrane pressure] or water permeability may be adapted to the present dialysis settings and be of value in clinics.
  
  
  
  GKD-UF was determined and its reproducibility, variability and influencing factors were specifically assessed in 15 stable patients routinely treated by high-flux haemodialysis or HC-HDF in a single unit.
  
  
  
  GKD-UF invariably followed a parabolic function with increasing QUF in dialysis and both pre- and post-dilution HC-HDF (R2 constantly >0.96). The vertex of the parabola, GKD-UF-max and related QUF were very reproducible per patient (coefficient of variation 3.9 ± 0.6 and 3.3 ± 0.3%, respectively) and they greatly varied across patients (31–42 mL/h−1/mmHg and 82–100 mL/min, respectively). GKD-UF-max and its associated QUF decreased during dialysis treatment (P < 0.01). The GKD-UF-max decrease was related to weight loss (R2 = 0.66; P = 0.0015).
  
  
  
  GKD-UF is a reliable and accurate method to assess the water permeability of a system in vivo. It varies according to dialysis setting and patient-related factors. It is an objective parameter evaluating the forces driving convection and identifies any diversion of the system during the treatment procedure. It is applicable to low- or high-flux dialysis as well as pre- or post-dilution HDF. Thus, it may be used to describe the characteristics of a dialysis system, is suitable for clinical use and may be of help for personalized prescription.
authors.affiliation: RD - Néphrologie and Groupe Rein et HTA, EA7288, Université de Montpellier, Montpellier cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Ficheux
authors.affiliation: RD - Néphrologie and Groupe Rein et HTA, EA7288, Université de Montpellier, Montpellier cedex, France.
authors.forename: N
authors.initials: N
authors.lastname: Gayrard
authors.affiliation: RD - Néphrologie and Groupe Rein et HTA, EA7288, Université de Montpellier, Montpellier cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Duranton
authors.affiliation: RD - Néphrologie and Groupe Rein et HTA, EA7288, Université de Montpellier, Montpellier cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Guzman
authors.affiliation: Centre de dialyse de Sète, Néphrologie Dialyse St Guilhem, Sète, France.
authors.forename: I
authors.initials: I
authors.lastname: Szwarc
authors.affiliation: Centre de dialyse de Sète, Néphrologie Dialyse St Guilhem, Sète, France.
authors.forename: F
authors.initials: F
authors.lastname: Vetromile
authors.affiliation: Service de Néphrologie, Hôpital de La Conception, Université Aix-Marseille, Marseille, France.
authors.forename: P
authors.initials: P
authors.lastname: Brunet
authors.affiliation: Centre de dialyse de Sète, Néphrologie Dialyse St Guilhem, Sète, France.
authors.forename: M F
authors.initials: MF
authors.lastname: Servel
authors.affiliation: RD - Néphrologie and Groupe Rein et HTA, EA7288, Université de Montpellier, Montpellier cedex, France.|Centre de dialyse de Sète, Néphrologie Dialyse St Guilhem, Sète, France.
authors.forename: A
authors.initials: A
authors.lastname: Argilés
mesh_terms: D018481:Convection; D005260:Female; D017583:Hemodiafiltration / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010539:Permeability; D011446:Prospective Studies; D011788:Quality of Life; D006435:Renal Dialysis / Q000379:methods*; D014462:Ultrafiltration; D014867:Water
chemical_list: D014867:Water
keywords: haemodiafiltration; high convection volumes; GKD-UF-max