Clinical evidence on haemodiafiltration.

Haemodiafiltration (HDF) combines diffusive and convective solute removal in a single treatment session. HDF provides a greater removal of higher molecular weight uraemic retention solutes than conventional high-flux haemodialysis (HD). Recently completed randomized clinical trials suggest better patient survival with online HDF. The treatment is mainly used in Europe and Japan. This review gives a brief overview of the presently available evidence of the effects of HDF on clinical end points, it speculates on possible mechanisms of a beneficial effect of HDF as compared with standard HD and ends with some perspectives for the future.

Platelet activation during haemodialysis: comparison of cuprammonium rayon and polysulfone membranes.

BACKGROUND/AIM: Haemodialysis-treated patients are at a high risk of developing cardiovascular disease. Part of this risk may be attributable to the type of the dialysis membrane used. We evaluated whether different dialysis membranes differ with respect to platelet activation. METHODS: In a randomized crossover trial, the platelet activation was measured in 14 patients treated with two different dialyzers (cuprammonium rayon membrane and polysulfone membrane). We compared the platelet activation over the dialyzer and between dialyzers after several weeks of dialysis. RESULTS: There were no differences between the two dialyzers in platelet activation over the dialyzer. After 2 weeks, however, the expression of CD62P, CD63, and PAC-1 was statistically significantly lower after cuprammonium membrane treatment than after polysulfone membrane treatment (mean fluorescence intensity in arbitrary units 8.0 vs. 11.1, 2.64 vs. 4.01, and 5.61 vs. 9.74, respectively). CONCLUSION: Dialysis with a polysulfone membrane seems to lead to more platelet activation than dialysis with a cuprammonium membrane.

Plasma dimethylarginine levels in chronic hemodialysis patients are independent of the type of dialyzer applied.

BACKGROUND: Asymmetric dimethylarginine (ADMA) levels are increased in hemodialysis (HD) patients. Reports on the effect of various dialysis strategies on ADMA, symmetric dimethylarginine (SDMA) and L-arginine levels are inconclusive. PATIENTS/METHODS: In this randomized crossover study, 15 patients were dialyzed for 4 weeks with 4 dialyzers, differing in biocompatibility and flux. Dimethylarginine and L-arginine levels were assessed at baseline, and after 4 weeks both before and after HD. RESULTS: During HD, ADMA and SDMA levels decreased significantly with all dialyzers. Dimethylarginine and L-arginine levels remained stable after 4 weeks of HD with each membrane. After pooling all data, values were mainly explained by variation between time points and patients, not by the type of dialyzer. CONCLUSION: Despite an intradialytic decrease in dimethylarginines, no changes occurred after 4 weeks of HD with either membrane. Furthermore, the variability of AMDA, SDMA and L-arginine levels was far more dependent on patient-related factors than on the type of dialyzer applied.

Influence of different haemodialysis modalities on AGE peptide levels: intradialytic versus long-term results.

BACKGROUND: Peptide-linked degradation products of advanced glycation end products (AGE peptides) accumulate in chronic haemodialysis (HD) patients and may contribute to a number of HD-related long-term complications, such as accelerated atherosclerosis. METHODS: The influence of a single HD session versus long-term HD on serum AGE peptides was determined. The patients were randomized to HD with a low-flux polysulfone (PS; F 6HPS), a high-flux PS (F 60S), a superflux PS (F 500S), or a superflux cellulose triacetate (CTA; Tricea 150G) dialyzer. RESULTS: During a single HD session, both AGE peptides and reference peptides decreased significantly (AGE peptides: Tricea 150G -37.0 +/- 2.9%; F 6HPS -35.5 +/- 2.4%; F 60S -39.5 +/- 4.7%, and F 500S -43.3 +/- 2.1%, p = 0.005; reference peptides: Tricea 150G -73.2 +/- 8.8%; F 6HPS -73.2 +/- 7.9%; F 60S -72.5 +/- 8.2%, and F 500S -74.1 +/- 7.3%, p = 0.005). After 12 weeks of HD with the superflux CTA, the AGE peptide levels decreased significantly (week 1: 2.7 +/- 1.1 arbitrary units, week 12: 2.5 +/- 1.2 arbitrary units, decrease 7.4%; p = 0.01), whereas the AGE peptide levels remained unchanged after HD with each of the other three modalities. The reference peptide levels did not change after 12 weeks of HD. CONCLUSION: Although AGE peptides can be effectively removed during a single HD session, superflux CTA seems to be the only modality capable of reducing AGE peptides in the long term.

Enhanced long-term reduction of plasma leptin concentrations by super-flux polysulfone dialysers.

BACKGROUND: Hyperleptinaemia in chronic haemodialysis (CHD) patients has been associated with malnutrition, which is an independent predictor of morbidity and mortality in this patient group. METHODS: To assess the influence of HD on plasma leptin, 10 CHD patients were crossover randomized to low-flux polysulfone (PS: F 6HPS), high-flux PS (F 60S), super-flux PS (F 500S) or super-flux cellulose-tri-acetate (CTA: Tricea 150G) for 12 weeks each. Blood samples were collected at the start of the study and each 12-week period. In addition, the relationship between patient characteristics, inflammation and leptin was analysed. RESULTS: At baseline, all groups showed similar leptin concentrations (mean 33.6+/-21.7 ng/ml). After a single HD session, a significant (P<0.01) decrease was observed with all three high permeable devices (Tricea 150G -52.7+/-6.4%; F 60S -63.1+/-5.7%; F 500S -68.7+/-8.2%), whereas leptin remained stable with low-flux PS. After 12 weeks, a marked increase was observed with low-flux PS (week 1, 30.4+/-23.0; week 12, 40.5+/-5.4 ng/ml, P = 0.05), no change with super-flux CTA and high-flux PS (Tricea 150G week 1, 29.4+/-23.7; week 12, 32.0+/-27.9 ng/ml, P = ns; F 60S week 1, 36.0+/-31.8; week 12, 33.0+/-31.2 ng/ml, P = ns), and a significant decrease with super-flux PS (week 1, 38.3+/-33.0; week 12, 29.5+/-31.9 ng/ml, P = 0.02). The change in leptin after 12 weeks was significantly different between super-flux PS, and both low-flux PS (P = 0.009) and super-flux CTA (P = 0.01). Besides interleukin-6 (IL-6) at the start of the study (P = 0.006), no correlations were observed between patient characteristics, parameters of inflammation and plasma leptin levels. CONCLUSIONS: Apart from low-flux PS, plasma leptin decreased considerably with all three high permeable dialysers after a single HD session. In the long run, leptin levels were lower with high-flux PS than with low-flux PS. Moreover, after switching from high-flux PS to super-flux PS (but not super-flux CTA), an additional decrease in leptin was observed. Apart from IL-6 at the start of the study, neither patient characteristics nor inflammatory parameters correlated with plasma leptin levels in this patient group.