title: [On-line haemodiafiltration with sorbent-regenerated ultrafiltrate as replacement fluid: Beta2-microglobulin removal versus filtration fraction].
abstract: OBJECTIVE
  In order to encourage the removal of middle molecules in hemodiafiltration (HDF) techniques an attempt is made to maximize convective clearance by increasing the ultrafiltration rate. However, convective clearance is limited by the maximum filtration fraction (FF%) obtainable, by the pre- or post reinfusion method and by the convective surface and the capacity of the filter used. This study aimed to evaluate the effect of the FF% in the removal of Beta2-microglobulin (Beta2-m) during hemodiafiltration reinfusion (HFR) to identify the best ultrafiltration strategies; and therefore, a better removal of medium molecular weight solutes in this hemodiafiltrative technique recently introduced in clinical practice.
  
  
  METHODS
  Ten chronic uremic patients (eight males, two females; age 66 +/- 18 yrs) already on renal dialysis therapy (RDT) for 80 +/- 36 months, were subjected to four HFR sessions, with Td=240 +/- 10 min, Qb=312 +/- 18 and Qd=500 mL/min; the reinfusion rates (Qr) used were 43.6 +/- 7.2 mL/min (25-58) with FF% rates varying from 20-34 (24.2 +/- 3.8) for hematocritic levels of 34.6 +/- 4.2% at the start of the dialysis session. For each session the intradialytic reduction rates (RR%) of urea, creatinine (Cr), phosphate, uric acid and Beta2-m and its average clearance (KBeta2-m mL/min) were evaluated.
  
  
  RESULTS
  The results obtained gave a RR% for urea of 69.4 +/- 5 (Kt/Veq=1.23 +/- 0.2) and for Cr, phosphate and uric acid values of, respectively, 61.2 +/- 5.4, 47.5 +/- 10 and 75.8 +/- 6.7. The intradialytic reductions in Beta2-m were 49.3 +/- 10.3% with a variability range from 29-69% and with average KBeta2-m values of 63.8 +/- 13.5 mL/min. The RR% of ss2-m and KBeta2-m were inversely correlated (p<0.01) to the FF% rate applied during the treatment; 75% of the HRF sessions in which we observed a reduction in Beta2-m levels >40% were those where a FF% between 20 and 26% was applied. CONCLUSIONS. From our study, it appears that in HFR the best ultrafiltration strategy from the convective sector in removing Beta2-m has FF% values in the range 20-26%. The occurrence of lower intradialytic reductions of Beta2-m with increasing FF% can be interpreted as a consequence of phenomena related to high intradialytic hemoconcentrations, to the excessive increase in the TMP and/or the increase in the protein cake with a consequent reduction in permeability and mass transfer. Although using a limited convective surface with a limited possibility of increasing the FF%, nevertheless, HFR seems capable of ensuring a satisfactory uremic toxin removal of low and medium molecular weight, which combined with the high biocompatibility deriving from the use of reinfused endogen, can be considered an effective dialytic strategy for preventing or retarding the complications in dialytic patients.
authors.affiliation: U.O. Aziendale di Nefrologia e Dialisi, Ospedale S. Maria delle Croci, Ravenna. g.emiliani@ausl.ra.it
authors.forename: G
authors.initials: G
authors.lastname: Emiliani
authors.forename: M
authors.initials: M
authors.lastname: Briganti
authors.forename: A
authors.initials: A
authors.lastname: Montanari
authors.forename: E
authors.initials: E
authors.lastname: Isola
authors.forename: M
authors.initials: M
authors.lastname: Fusaroli
mesh_terms: D000368:Aged; D005260:Female; D017583:Hemodiafiltration / Q000379:methods*; D015312:Hemodialysis Solutions / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D014511:Uremia / Q000378:metabolism* / Q000628:therapy*; D001613:beta 2-Microglobulin / Q000378:metabolism*
chemical_list: D015312:Hemodialysis Solutions; D001613:beta 2-Microglobulin