Efficiency of Post-Dilution Hemodiafiltration with a High-Flux α-Polysulfone Dialyzer

Abstract

Purpose

Intra-individual comparison of technical and clinical characteristics of two hemodiafiltration (HDF) strategies, namely, post-dilution HDF (post-HDF) with a high-flux α-polysulfone hemodiafilter and reverse mid-dilution HDF (MD-HDF).

Methods

Fifteen patients who were stable on RRT were randomly submitted to both HDF techniques under matched operational conditions. Removal of small and middle molecular compounds was compared. The pressure regimen within the dialyzers and the hydraulic and solute permeability indexes of the membrane were monitored on-line during the sessions.

Results

Urea removed was not statistically different between post-HDF and MD-HDF (41.7±10.2 vs. 39.9±8.2 g/session). High and comparable removal of phosphate (K_DQ,132±30 vs. 138±21 ml/min) and middle molecules (β₂-m K_DQ, 79.1±6.1 vs. 74.1±13.5 ml/min) was shown in post-HDF and MD-HDF. Albumin leakage tended to be lower after post-HDF (914±370 vs. 1313±603 mg/session, p=0.075). There were no cases of blood circuit clotting, hypotensive episodes, or other clinical or technical problems. In post-HDF, a very high ultrafiltration rate (Q_UF, 7.4 l/h) and filtration fraction of 59% were maintained through the sessions with safe trans-membrane pressure (TMP) values strictly retained within the planned range (280–350 mmHg). Larger volume exchange (10 l/h) was obtained in MD-HDF, but the very high Q_UF established high and risky TMP in the post-dilution section of the MD 220 dialyzer.

Conclusions

The hemodiafilter tested in this study proved its high efficiency when used in post-dilution HDF with the application of an automatic ultrafiltration/pressure feedback, which guaranteed maximal convection within controlled hydraulic conditions.