title: On-line haemodiafiltration with auto-substitution: assessment of blood flow changes on convective volume and efficiency.
abstract: BACKGROUND
  On-line haemodiafiltration (OL-HDF) is currently the most effective technique and several randomised studies and meta-analyses have seen a reduction in mortality and an association directly related with convective volume is observed. Blood flow (Qb) limits the infusion rate to 25-33 % and is the main limiting factor for reaching an optimum substitution volume. With the recent incorporation of monitors with auto-substitution systems, the aim of the study was to assess the effect of Qb variations on convective volume and purifying capacity.
  
  
  METHODS
  23 patients, 17 men and 6 women, were included, with an average age of 65.5 &plusmn;10 years, time on dialysis 292.2 &plusmn; 15 minutes, which were in the OL-HDF programme with the 5008 Cordiax monitor with auto-substitution. Each patient was analysed over 5 sessions in which only the Qb was changed (250, 300, 350, 400 and 450 ml/min). In each session the substitution volume, total convective volume and parameters of dialysis were measured. The concentration of urea (60 Da), creatinine (113 Da), &beta;2-microglobulin (11,800 Da), myoglobin (17,200 Da), prolactin (23,000 Da), &alpha;1-microglobulin (33,000 Da) and &alpha;1-acid glycoprotein (40,000 Da) in plasma was measured at the start and end of each session in order to calculate the percentage of reduction of these solutes.
  
  
  RESULTS
  The trans-membrane pressure was less, with Qb 250 ml/min. A significant increase in convective volume was observed with the increase in Qb, 23.7, 26.9, 30.2, 32.8 and 35.2 l/session to 250, 300, 350, 400 and 450 ml/min, respectively (P &lt; 0.001), representing a percentage of total purified blood of 33.2, 31.2, 30.2, 28.7 and 27.3 % respectively. The percentages of reduction of urea and creatine progressively increased with Qb, slight differences were observed with &beta;2-microglobulin and myoglobin, and no changes were observed in the larger molecules.
  
  
  CONCLUSIONS
  For each 50 ml/min increase in Qb, the convective volume increased by between 8 and 12 ml/min. The auto-substitution system strengthens the lowest Qbs in the percentage of convective volume with regards to total purified blood. Qb increases the purifying capacity of small molecules, favouring that of &beta;2-microglobulin and myoglobin, and does not influence molecules of a greater molecular weight.&nbsp;
authors.forename: Francisco
authors.initials: F
authors.lastname: Maduell
authors.forename: Raquel
authors.initials: R
authors.lastname: Ojeda
authors.forename: Lida
authors.initials: L
authors.lastname: Rodas
authors.forename: Nayra
authors.initials: N
authors.lastname: Rico
authors.forename: Néstor
authors.initials: N
authors.lastname: Fontseré
authors.forename: Marta
authors.initials: M
authors.lastname: Arias
authors.forename: Manel
authors.initials: M
authors.lastname: Vera
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Massó
authors.forename: Mario
authors.initials: M
authors.lastname: Jiménez-Hernández
authors.forename: M Florencia
authors.initials: MF
authors.lastname: Rossi
authors.forename: Giannina
authors.initials: G
authors.lastname: Bazán
authors.forename: Josep M
authors.initials: JM
authors.lastname: Campistol
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D005260:Female; D017583:Hemodiafiltration / Q000379:methods*; D006439:Hemodynamics; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009862:Online Systems; D006435:Renal Dialysis
chemical_list: D015415:Biomarkers