Background: Chronic hemodialysis patients have higher cardiovascular morbidity compared to the general population. A number of studies have suggested that patients undergoing hemodialysis with polymethylmethacrylate (PMMA) membranes have a better outcome compared to other membranes. Methods: We performed a retrospective, multicenter study to evaluate the impact of PMMA membranes compared to other types of membranes on clinical parameters considered important risk factors for the development of cardiovascular disease in chronic kidney disease patients. Results: The study included 104 patients (52 patients on PMMA and 52 patients on other membranes) from ten dialysis centers, monitored for 24 months. HDL cholesterol (mg/dL) increased significantly in the PMMA group (41.4 ± 10.8 to 44.1 ± 13.5, p = 0.0467), but not in the control group (41.8 ± 13.8 to 39.4 ± 9.6, p = 0.8628). At 24 months total cholesterol and triglycerides (mg/dl) were significantly lower in the PMMA group than in the control group (142.4 ± 43.8 vs. 166.1 ± 43.4, p = 0.0321 and 106 (76.5-176) vs. 170 (118-254), p = 0.014), respectively. Serum creatinine (mg/dL) increased significantly from baseline to 24months in the PMMA group (9.20 ± 2.5 to 9.47 ± 2.3, p = 0.0291), but not in the patients treated with other membranes (8.39 ± 2.6 to 8.37 ± 2.3, p = 0.2743). In addition creatinine was significantly higher in the PMMA group compared to the other group (9.47 ± 2.3 vs. 8.37 ± 2.3, p = 0.0493). WBCs (109/L) increased significantly in the control group (6151 ± 1846 to 6672 ± 1872, p = 0.0457) but not in the PMMA group (6326 ± 2113 to 6152 ± 1832, p = 0.8981). At 24 months platelets (109/L) and CRP (ng/dL) were significantly lower in the PMMA group compared to the control group (185 (144-222) vs. 210 (173-259), p = 0.0498 and 0.70 (0.30-1.59) vs. 3.76 (0.46-10.2), p = 0.023, respectively). Iron and transferrin (μ g/dL) decreased signifi cantly in the patients treated with other membrane (62.5 ± 30.4 to 52.6 ±19.0, p = 0.0113 and 178 (157-218) to 170 (124-203), p = 0.0019, respectively), but not in the PMMA group. Conclusion: This retrospective study of data from 104 patients shows a favorable effect of PMMA on clinical variables considered relevant for the development of atherosclerosis in hemodialysis patients.

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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 m 2 Baxter.Materials and methods: Four patients in chronic threeweekly 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.