In vivo solute elimination of paired filtration dialysis

Paired filtration dialysis (PFD) is a new dialysis strategy whereby a hemofilter and a hemodialyzer are coupled in series. It has been assumed that this approach allows a better solute elimination than conventional hemodialysis (HD), allowing a shortening of dialysis time. To evaluate this hypothesis, solute elimination with PFD either with 0.4 m2 polysulphone (PS) and 1.36 m2 cuprophan (CU) 3x3 h/wk, or with 0.4 m2 PS and 1.06 m2 CU 3x4 h/wk, was compared to HD with 1.36 m2 CU, 3x4 hours weekly in the same patients. During PFD, 10L were ultrafiltered and substituted by saline. Overall extraction of UV absorbing solutes (MW less than 10,000 Dalton), and extraction of individual solutes identified by high performance liquid chromatography (HPLC) were compared as well as urea kinetics. For PFD 3x3 h overall extraction of UV-absorbing compounds and of hippuric acid was significantly higher than for HD 3x4 h (p less than 0.05). Overall extraction of UV-absorbing compounds and of all but one individual compound under study was markedly higher for PFD 3x4 h vs conventional HD 3x4 h (p less than 0.01), in spite of a higher diffusive area with the latter technique. No differences in urea kinetics were observed for the 3 strategies. It is concluded that solute extraction during PFD is higher than during HD, if the treatment time is the same. Even if treatment is shortened to 3x3 h weekly, solute extraction with PFD is at least as efficient as with HD.