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Dialyzers are classified into five types based on their ß2-microglobulin clearance rate and albumin sieving coefficient: Ia, Ib, IIa, and IIb. In addition, a new classification system introduced a type S dialyzer. However, limited information is available regarding the impact of dialyzer type on patient outcomes. A cohort study was conducted using data from the Japanese Society for Dialysis Therapy Renal Data Registry database. Total 181,804 patients on hemodialysis (HD) were included in the study, categorized into four groups (type Ia, IIa, IIb, and S). The associations between each group and two-year all-cause mortality were assessed using Cox proportional hazard models. Furthermore, propensity score-matching analysis was performed. By the end of 2019, 34,185 patients on dialysis had died. After adjusting for all confounders, the risk for all-cause mortality was significantly lower in the type IIa, and S groups than in the type Ia group. These significant findings were consistent after propensity score matching. In conclusion, our findings suggest that super high-flux dialyzers, with a ß2-microglobulin clearance of ≥ 70 mL/min, may be beneficial for patients on HD, regardless of their albumin sieving coefficient. In addition, type S dialyzers may be beneficial for elderly and malnourished patients on dialysis.Trial registration number: UMIN000018641.

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Background: We aimed to investigate the change in the large middle molecule (>15 kDa) removal rate, which is associated with vascular calcification, when using a medium cut-off (MCO) dialyzer compared to a high-flux (HF) dialyzer. Methods: Twenty patients with clinically stable maintenance hemodialysis were investigated over a 15-week study period. Dialyzer efficacies were evaluated during the last midweek hemodialysis treatment for each consecutive dialyzer membrane use: 1st HF, MCO, and 2nd HF dialyzer; 5 weeks each period. Changes in α1-microglobulin (33 kDa) during a dialysis session were analyzed to assess the efficacy of the MCO dialyzer as a reference. The levels and reduction ratios of fibroblast growth factor 23 (FGF23, 32 kDa), osteoprotegerin (OPG, 60 kDa), and sclerostin (22 kDa) were analyzed. Large middle molecules were measured using an enzyme-linked immunosorbent assay. Results: Serum hemoglobin, phosphorus, and corrected calcium levels were not significantly different for each dialyzer period. Total protein and albumin values during the MCO dialyzer period did not decrease compared with the HF dialyzer period. The reduction ratio of α1-microglobulin was significantly higher in the MCO dialyzer than in the HF dialyzer (p < 0.001). The reduction ratios of FGF23 (p < 0.001), OPG (p < 0.001), and sclerostin (p < 0.001) were significantly higher in the MCO dialyzer than those in the HF dialyzer. Conclusion: The reduction rate of large middle molecules related to vascular calcification, such as FGF23, OPG, and sclerostin, was significantly higher when using the MCO dialyzer than the HF dialyzer.

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INTRODUCTION: Medium cut-off (MCO) membranes may be able to remove middle-large uremic toxins that are retained in the body, which has been linked to various risk factors including malnutrition-inflammation score (MIS). The effect of MCO dialyzers on MIS has been studied. METHODS: This single-center exploratory prospective observational study enrolled maintenance hemodialysis patients who underwent dialysis using either MCO (Theranova 400) or high-flux (FX80) membranes as part of their regular care. Measurements of MIS, body weight, height, body mass index, and various biochemical markers were taken at the beginning and conclusion of the study. RESULTS: This study included 50 patients who were treated with either the Theranova 400 (n = 25) or the FX80 (n = 25) for a period of 6 months. The two groups were similar in terms of demographics, duration of hemodialysis treatment, and baseline biochemical test results. Theranova 400 had no significant impact on the median MIS (6 [6-10] vs. 7 [5-10], p 0.575) and serum albumin levels (4.07 [3.92-4.22] vs. 4.04 [3.85-4.30], p 0.689), while the FX80 resulted in a significant increase in MIS (6 [5-8] vs. 8 [6-10], p 0.033) and a significant decrease in serum albumin levels (4.23 [4.03-4.36] vs. 3.98 [3.77-4.12], p 0.027) at the end of the study. DISCUSSION/CONCLUSION: After 6 months of treatment, the MCO dialyzer did not demonstrate a statistically significant difference in the MIS when compared to the high-flux dialyzer. However, MIS worsening was significantly less in the MCO group, indicating the potential benefits of MCO membranes in maintaining nutritional status. Further research is required to validate these results.

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The mechanisms behind reported decreases in plasma insulin and glucagon during hemodialysis (HD) are not clear. Here, we investigated these mechanisms during HD treatment and the characteristics of insulin and glucagon removal when using two super high-flux membranes. In an experimental study, clearance, adsorption rates, and reduction rates of insulin and glucagon were investigated when using cellulose triacetate (CTA) and polysulfone (PS) membranes in a closed circuit using bovine blood. In a clinical study, 20 diabetes patients with end-stage kidney disease who were stable on HD were randomly selected for two HD sessions with two different membranes. At 1 h after the initiation of HD, insulin and glucagon clearance were measured, and the reduction rates were also investigated. In the experimental study, the PS membrane showed significantly higher clearance, adsorption rates, and reduction rates of insulin and glucagon compared with the CTA membrane. Although glucagon was detected in the ultrafiltration fluids in both membranes, insulin was absent in the PS membrane. In the clinical study, both membranes showed significant reductions in plasma insulin and glucagon at each time point. The PS membrane showed significantly higher insulin clearance and reduction rates compared with the CTA membrane. The two membranes showed no significant difference in glucagon clearance, but the glucagon reduction rate was significantly higher with the PS membrane. Our findings show that HD with the two super high-flux membranes used removes significant amounts of glucoregulatory peptide hormones from plasma in patients with diabetes and end-stage kidney disease, potentially affecting their glucose metabolism.

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INTRODUCTION: In Japan, dialyzers are classified based on ß2-microglobulin clearance. Type I dialyzers are classified as low-flux dialyzers (<10 mL/min clearance), type II and III as high-flux dialyzers (≥10 to <30 mL/min and ≥30 to <50 mL/min clearance, respectively), and type IV and V as super high-flux dialyzers (≥50 to <70 mL/min and ≥70 mL/min clearance, respectively). Super high-flux dialyzers are commonly used, but their superiority over low-flux dialyzers is controversial. METHODS: In this nationwide prospective cohort study, we analyzed Japanese Society for Dialysis Therapy Renal Data Registry data collected at the end of 2008 and 2011. We enrolled 242,467 patients on maintenance hemodialysis and divided them into five groups by dialyzer type. We assessed the associations of each dialyzer type with 3-year all-cause mortality using Cox proportional hazards models and performed propensity score matching analysis, adjusting for potential confounders. RESULTS: By the end of 2011, 53,172 (21.9%) prevalent dialysis patients had died. Mortality significantly decreased according to dialyzer type. Hazard ratios (HRs) were significantly higher for type I, II and III compared with type IV (reference) after adjustment for basic factors and further adjustment for dialysis-related factors. HR was significantly higher for type I, but significantly lower for type V, after further adjustment for nutrition- and inflammation-related factors. These significant findings were also evident after propensity score matching. CONCLUSIONS: Hemodialysis using super high-flux dialyzers might reduce mortality. Randomized controlled trials are warranted to clarify whether these type V dialyzers can improve prognosis.

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BACKGROUND: Hemodialysis (HD) using super high-flux dialyzer (HD + SHF) comparably removed uremic toxins to high-volume postdilution online hemodiafiltration (olHDF). Integration of hemoperfusion (HP) to HD + SHF (HD + SHF + HP) might provide superior uremic toxin removing capability to high-volume postdilution olHDF. METHOD: The present study was conducted in thrice-a-week HD patients to compare the efficacy in removing indoxyl sulfate (IS), beta-2 microglobulin (ß2 M), and urea between high-volume postdilution ol-HDF and HD + SHF + HP, comprising HD + SHF as the main treatment plus HD + SHF + HP 1/week in the first 4 weeks and 1/2 weeks in the second 4 weeks. RESULTS: Ten prevalent HD patients with blood flow rate (BFR) above 400 ml/min were randomized into two sequences of 8-week treatment periods of HD + SHF + HP and later high-volume postdilution olHDF or vice versa. When compared with high-volume postdilution olHDF (convective volume of 26.02 ± 1.8 L/session), HD + SHF + HP provided comparable values of percentage reduction ratio of IS (52.0 ± 11.7 vs. 56.3 ± 7.5%, p = 0.14) and ß2 M (83.7 ± 4.9 vs. 84.0 ± 4.3%, p = 0.37) and slightly lower urea reduction ratio. Despite greater dialysate albumin loss (p = 0.008), there was no significant change in serum albumin level in HD + SHF + HP group. CONCLUSIONS: HD + SHF + HP could not provide superior efficacy in removing uremic toxins to high-volume postdilution olHDF. The use of low BFR of 200 ml/min during the first 2 h of HD + SHF + HP session, according to the instruction of manufacturer, might impair the efficacy of the HD + SHF part in removing uremic toxins.

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Background: Dialyzers are classified as low-flux, high-flux, and protein-leaking membrane dialyzers internationally and as types I, II, III, IV, and V based on ß2-microglobulin clearance rate in Japan. Type I dialyzers correspond to low-flux membrane dialyzers, types II and III to high-flux membrane dialyzers, and types IV and V to protein-leaking membrane dialyzers. Here we aimed to clarify the association of dialyzer type with mortality. Methods: This nationwide retrospective cohort study analyzed data from the Japanese Society for Dialysis Therapy Renal Data Registry from 2010 to 2013. We enrolled 238,321 patients on hemodialysis who were divided into low-flux, high-flux, and protein-leaking groups in the international classification and into type I to V groups in the Japanese classification. We assessed the associations of each group with 3-year all-cause mortality using Cox proportional hazards models and performed propensity score matching analysis. Results: By the end of 2013, 55,308 prevalent dialysis patients (23.2%) had died. In the international classification subgroup analysis, the hazard ratio (95% confidence interval) was significantly higher in the low-flux group [1.12 (1.03-1.22), P = 0.009] and significantly lower in the protein-leaking group [0.95 (0.92-0.98), P = 0.006] compared with the high-flux group after adjustment for all confounders. In the Japanese classification subgroup analysis, the hazard ratios were significantly higher for types I [1.10 (1.02-1.19), P = 0.015] and II [1.10 (1.02-1.39), P = 0.014] but significantly lower for type V [0.91 (0.88-0.94), P < 0.0001] compared with type IV after adjustment for all confounders. These significant findings persisted after propensity score matching under both classifications. Conclusions: Hemodialysis using protein-leaking dialyzers might reduce mortality rates. Furthermore, type V dialyzers are superior to type IV dialyzers in hemodialysis patients.

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The aim of this study was to examine the relationship between hydrostatic trans-membrane pressure (TMPh ) and colloid osmotic pressure (COP) in low-flux (LF) and high-flux (HF) dialyzers. Hydrostatic pressures were measured in dialyzers distinguished by their ultrafiltration coefficient Kuf (16 and 85 mL/h/mm Hg) under constant dialysate flow and variable blood flow (Qb ) ranging from 0 to 400 mL/min using (i) alginate (70 kDa) dissolved in dialysate, (ii) diluted, undiluted, and concentrated plasma, or (iii) whole blood at different hematocrit, all in absence of ultrafiltration (UF). For a given fluid, TMPh linearly increased with increasing Qb . The intercept of the linear TMPh to Qb relationship correlated with measured COP with an average bias of 1.00 ± 2.26 mm Hg and a concordance correlation coefficient of 0.98. The slope of the linear TMPh to Qb relationship increased with increasing sample viscosity and was much larger in HF dialyzers under otherwise identical operating conditions, most likely because of increased internal filtration. The TMPh to Qb relationship measured in dialyzers in absence of UF can be described by the intercept related to measured COP and the slope related to internal filtration. This relationship could be of interest to estimate internal filtration and COP under in vivo conditions.

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BACKGROUND: Hemodialysis is a process of removing waste and excess fluid from blood when kidneys cannot function efficiently. It often involves diverting blood to the filter of the dialysis machin to be cleared of toxic substances. Fouling of pores in dialysis membrane caused by adhesion of plasma protein and other toxins will reduce the efficacy of the filtre. OBJECTIVE: In This study, the influence of pulsed ultrasound waves on diffusion and the prevention of fouling in the filter membrane were investigated. MATERIAL AND METHODS: Pulsed ultrasound waves with frequency of 1 MHz at an intensity of 1 W/cm2 was applied to the high flux (PES 130) filter. Blood and blood equivalent solutions were passed through the filter in separate experimental setups. The amount of Creatinine, Urea and Inulin cleared from both blood equvalent solution and human whole blood passed through High Flux (PES 130) filter were measured in the presence and absence of ultrasound irradiation. Samples were taken from the outlet of the dialyzer every five minutes and the clearance of each constituent was calculated. RESULTS: Statistical analysis of the blood equvalent solution and whole blood indicated the clearance of Urea and Inulin in the presence of ultrasound increased (p<0.05), while no significant effects were observed for Creatinine. CONCLUSION: It may be concluded that ultrasound, as a mechanical force, can increase the rate of clearance of some toxins (such as middle and large molecules) in the hemodialysis process.

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BACKGROUND: The reprocess by citric acid and heat is an alternative to chemical reprocess for reusing dialyzers. However, there are little experience and data on the effect of reprocess by citric acid and heat on the solute clearance. METHODS: In the 34 chronic hemodialysis patients using low flux dialyzers, solute clearance was measured after reprocessing high-flux dialyzers by citric acid and heat. Dialyzers were reprocessed using 1.5% citric acid solution heated to 95degrees C for 20 hours. The clearance and reduction rate of urea, beta2-microglobulin, osteocalcin and myoglobin were measured at single use and during reuses for 5,10,15,20 and 25 times. RESULTS: The clearance and reduction rate of urea, beta2-microglobulin, osteocalcin and myoglobin were significantly greater with high-flux dialyzer compared with low flux dialyzer, which were maintained after dialyzer reuse. beta2-microglobulin clearance was increased at 10th and 20th reuse and beta2-microglobulin reduction rate was increased at 10th, 20th and 25th reuse compared with the single use. Myoglobin clearance and reduction rate were increased after the 5th reuse compared with the single use. Albumin loss to dialysate was gradually increased following reuses. Of the 34 dialyzers studied, 14 were discarded before the 25th reuse because of inadequate performance test. CONCLUSION: Reprocessing high flux dialyzers by citric acid and heat increases middle and large molecule clearance and was safe.

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BACKGROUND: The reprocess by citric acid and heat is an alternative to chemical reprocess for reusing dialyzers. However, there are little experience and data on the effect of reprocess by citric acid and heat on the solute clearance. METHODS: In the 34 chronic hemodialysis patients using low flux dialyzers, solute clearance was measured after reprocessing high-flux dialyzers by citric acid and heat. Dialyzers were reprocessed using 1.5% citric acid solution heated to 95degrees C for 20 hours. The clearance and reduction rate of urea, beta2-microglobulin, osteocalcin and myoglobin were measured at single use and during reuses for 5,10,15,20 and 25 times. RESULTS: The clearance and reduction rate of urea, beta2-microglobulin, osteocalcin and myoglobin were significantly greater with high-flux dialyzer compared with low flux dialyzer, which were maintained after dialyzer reuse. beta2-microglobulin clearance was increased at 10th and 20th reuse and beta2-microglobulin reduction rate was increased at 10th, 20th and 25th reuse compared with the single use. Myoglobin clearance and reduction rate were increased after the 5th reuse compared with the single use. Albumin loss to dialysate was gradually increased following reuses. Of the 34 dialyzers studied, 14 were discarded before the 25th reuse because of inadequate performance test. CONCLUSION: Reprocessing high flux dialyzers by citric acid and heat increases middle and large molecule clearance and was safe.