Purifying Capacity of a New Membrane Characterized by a Medium Cut-Off and High Performance

Introduction: The adsorbing capacity of membranes can be considered the third dimension of the depurative action of dialysis: diffusion, convection and adsorption. Some metabolites are almost totally bound to albumin, so, regardless of their molecular weight, removal with low flux or high flux dialysis membranes becomes difficult if not impossible. The aim of our work was to evaluate the adsorptive efficacy as well as the depurative of a new membrane with a medium cut-off: Theranova 400, PAES / PVP membrane with surface 1.7 m2 Baxter.

Materials and methods: Four patients in chronic three-weekly dialysis were evaluated for over 6 months, treated with the Theranova 400 dialyzer filter, for 6 dialysis bicarbonate sessions. In every piece, blood tests were performed at the beginning and end of dialysis, for the first 3 dialysis and at the third dialysis of the second week, to evaluate besides the purification of the main standard parameters, also the removal of medium molecular weight solutes such as myoglobin, beta2 microglobulin and solutes such as indoxyl sulfate (F IXS) and pcresol (F PCS) which represent less than 10% of the free fraction being bound to albumin for more than 90% of their total concentration (T IXS and T PCS). IXS and PCS were also measured at the biginning of the third dialysis session of the week , in other 130 ESRD patients treated with various membranes . The statistical differences, before and after dialysis, were calculated with the Student’s t test for paired data. For the comparison of the values between Theranova and other membranes the Mann Whitney U Test was used for nonparametric data.

Results: At the end of the 6 4-h hemodialysis sessions there was a significant decrease in both the low molecular weight parameters with a good KT/V and a urea clearance close to 300 ml/min. Mean MW concentrations were reduced by 50-75%, while F IXS, T IXS, F PCS and T PCS were reduced by more than 20%. The predialytic values of the last dialysis of the week tended to be higher and in some statistically significant in all the other membranes compared to Theranova.

Conclusions: In addition to the high diffusional purifying capacity, the membrane shows a marked adsorptive capacity demonstrated by the effective removal of metabolites linked to albumin and therefore more difficult to remove. It will be interesting to follow in time the adsorptive capacity of this membrane and its clinical implication, especially in comparisons of cardiovascular and atherosclerotic diseases that appear to be related to the concentrations of these metabolites, practically impossible to remove with standard membranes.


Chiara Ralli1, Diletta Duranti, Patrizio Imperiali, Marco Bagnati, Filomena Panza, Matteo Basile, Giorgio Bellomo and Ennio Duranti*

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