Dialyzer membrane characteristics and outcome of patients with type 2 diabetes on maintenance hemodialysis

Survival with low- and high-flux dialysis

Background

Besides advances in haemodialysis (HD), mortality rates are still high. The effect of the different types of HD membranes on survival is still a controversial issue. The aim of this COSMOS (Current management Of Secondary hyperparathyroidism: a Multicentre Observational Study) analysis was to survey, in HD patients, the relationship between the use of conventional low- or high-flux membranes and all-cause and cardiovascular mortality.

Methods

COSMOS is a multicentre, open-cohort, 3-year prospective study, designed to evaluate mineral and bone disorders in the European HD population. The present analysis included 5138 HD patients from 20 European countries, 3502 randomly selected at baseline (68.2%), plus 1636 new patients with <1 year on HD (31.8%) recruited to replace patients who died, were transplanted, switched to peritoneal dialysis or lost to follow-up by other reasons. Cox-regression analysis with time-dependent variables, propensity score matching and the use of an instrumental variable (facility-level analysis) were used.

Results

After adjustments using three different multivariate models, patients treated with high-flux membranes showed a lower all-cause and cardiovascular mortality risks {hazard ratio (HR) = 0.76 [95% confidence interval (CI) 0.61-0.96] and HR = 0.61 (95% CI 0.42-0.87), respectively}, that remained significant after matching by propensity score for all-cause mortality (HR = 0.69, 95% CI 0.52-0.93). However, a facility-level analysis showed no association between the case-mix-adjusted facility percentage of patients dialysed with high-flux membranes and all-cause and cardiovascular mortality.

Conclusions

High-flux dialysis was associated with a lower relative risk of all-cause and cardiovascular mortality. However, dialysis facilities using these dialysis membranes to a greater extent did not show better survival.

Clinical evaluation of performance, biocompatibility, and safety of vitamin E-bonded polysulfone membrane hemodialyzer compared to non-vitamin E-bonded hemodialyzer

The vitamin E-bonded polysulfone membrane hemodialyzer (ViE™-21) was evaluated in a clinical study for regulatory submission. Seventeen patients on hemodialysis were treated with conventional high-flux hemodialyzers for 2 weeks (Pre-ViE phase) and switched to the ViE-21 for 36 sessions (ViE phase) followed by an additional 2 weeks on conventional hemodialyzers (Post-ViE phase). Reduction ratios of urea, creatinine, beta-2-microglobulin, albumin, and ultrafiltration coefficients (KUF) were measured once during the Pre-ViE phase and twice during the ViE phase. Moreover, biocompatibility markers [leucocyte count, platelet count, and activated complement factor (C3a) levels] were evaluated pre-dialysis, 15 min after initiation, and post-dialysis. During the study, type and number of adverse events (AEs), and device malfunctions were recorded. ViE-21 reduction ratios and KUF were not noticeably different than those of conventional hemodialyzers. Fluctuations of leucocyte counts and C3a concentrations were similar using ViE-21 and conventional hemodialyzers; however, the platelet count fluctuation was lower in ViE-21 sessions. The frequency of episodes of hypotension occurring during the ViE phase was lower than that occurring during the Pre- and Post-ViE phases. In conclusion, this study provided performance and safety data of the ViE-21 for regulatory application. The data suggest that vitamin E-bonded hemodialyzers are beneficial in lowering platelet activation and frequency of intradialytic hypotension. Larger randomized controlled trials are needed to confirm these findings.

Acute effects of haemodialysis on circulating microparticles

Background

Microparticles (MPs) are small cell membrane-derived vesicles regarded as both biomarkers and mediators of biological effects. Elevated levels of MPs have previously been associated with endothelial dysfunction and predict cardiovascular death in patients with end-stage renal disease. The objective of this study was to measure change in MP concentrations in contemporary haemodialysis (HD).

Methods

Blood was sampled from 20 consecutive HD patients before and 1 h into the HD session. MPs were measured by flow cytometry and phenotyped based on surface markers.

Results

Concentrations of platelet (CD41⁺) (P = 0.039), endothelial (CD62E⁺) (P = 0.004) and monocyte-derived MPs (CD14⁺) (P < 0.001) significantly increased during HD. Similarly, endothelial- (P = 0.007) and monocyte-derived MPs (P = 0.001) expressing tissue factor (TF) significantly increased as well as MPs expressing Klotho (P = 0.003) and receptor for advanced glycation end products (RAGE) (P = 0.009). Furthermore, MPs expressing platelet activation markers P-selectin (P = 0.009) and CD40L (P = 0.045) also significantly increased. The increase of endothelial (P = 0.034), monocyte (P = 0.014) and RAGE⁺ MPs (P = 0.032) as well as TF⁺ platelet-derived MPs (P = 0.043) was significantly higher in patients treated with low-flux compared with high-flux dialysers.

Conclusion

Dialysis triggers release of MPs of various origins with marked differences between high-flux and low-flux dialysers. The MPs carry surface molecules that could possibly influence coagulation, inflammation, oxidative stress and endothelial dysfunction. The clinical impact of these findings remains to be established in future studies.

Internal Hemodiafiltration versus Low-Flux Bicarbonate Dialysis: Results from a Long-Term Prospective Study

Introduction

About ten years ago it was discovered that changes in filter design which increase passive filtration improved dialysis efficiency. Later, these modified membranes showed similar intradialytic efficiency when used in on-line hemodiafiltration or in bicarbonate dialysis, called internal hemodiafiltration.

Aim and Methods

On the basis of these previous results, we studied the long-term effects of internal hemodiafiltration, in comparison with low-flux bicarbonate dialysis. The pre-dialysis beta2-microglobulin level was chosen as the primary outcome variable. A prospective multicenter study with a cross-over scheme, 2 treatments and 3 periods, was designed. Twenty-four patients, followed in two dialysis centers, were enrolled. Many other parameters were measured every month at the first dialysis session of the week. The intra-dialytic removal of urea, beta2-microglobulin and homocysteine was also calculated.

Results

The removal of uremic toxins was significantly higher in internal hemodiafiltration than in low-flux bicarbonate dialysis. The pre-dialysis value of urea, phosphorus, beta2-microglobulin and homocysteine was lower during internal hemodiafiltration as compared with low-flux bicarbonate dialysis. The mean pre-dialysis value of hemoglobin was significantly higher during internal hemodiafiltration than low-flux bicarbonate dialysis, with a trend towards a significantly lower consumption of erythropoiesis stimulating agents during internal hemodiafiltration as compared with low-flux bicarbonate dialysis.

Conclusions

Long-term treatment with internal hemodiafiltration improves the removal of small molecules and stops the continuous increase of middle molecules as seen in low-flux bicarbonate dialysis. Internal hemodiafiltration may substitute low-flux bicarbonate dialysis, but we need new prospective studies about long-term hard end-points.

Performance of hemodialysis with novel medium cut-off dialyzers

Background. Compared to high-flux dialysis membranes, novel medium cut-off (MCO) membranes show greater permeability for larger middle molecules.

Methods. In two prospective, open-label, controlled, randomized, crossover pilot studies, 39 prevalent hemodialysis (HD) patients were studied in four dialysis treatments as follows: study 1, three MCO prototype dialyzers (AA, BB and CC with increasing permeability) and one high-flux dialyzer in HD; and study 2, two MCO prototype dialyzers (AA and BB) in HD and high-flux dialyzers in HD and hemodiafiltration (HDF). Primary outcome was lambda free light chain (λFLC) overall clearance. Secondary outcomes included overall clearances and pre-to-post-reduction ratios of middle and small molecules, and safety of MCO HD treatments.

Results. MCO HD provided greater λFLC overall clearance [least square mean (standard error)] as follows: study 1: MCO AA 8.5 (0.54), MCO BB 11.3 (0.51), MCO CC 15.0 (0.53) versus high-flux HD 3.6 (0.51) mL/min; study 2: MCO AA 10.0 (0.58), MCO BB 12.5 (0.57) versus high-flux HD 4.4 (0.57) and HDF 6.2 (0.58) mL/min. Differences between MCO and high-flux dialyzers were consistently significant in mixed model analysis (each P < 0.001). Reduction ratios of λFLC were greater for MCO. Clearances of α1-microglobulin, complement factor D, kappa FLC (κFLC) and myoglobin were generally greater with MCO than with high-flux HD and similar to or greater than clearances with HDF. Albumin loss was moderate with MCO, but greater than with high-flux HD and HDF.

Conclusions. MCO HD removes a wide range of middle molecules more effectively than high-flux HD and even exceeds the performance of high-volume HDF for large solutes, particularly λFLC.

[Online hemodiafiltration: Practical aspects, safety and efficacy]

Purification of high molecular uremic toxins by conventional hemodialysis is limited. It remains associated with a high morbidity and excessively high mortality. Online hemodiafiltration using a high permeability hemodiafilter, an ultrapure dialysate, and which tends to maximize substitution volumes, provides a high efficiency and low bio-incompatibility renal supplementation. Regular use of online hemodiafiltration is associated with reduced morbidity (reduction of intradialytic hypotension episodes, improved blood pressure control, reduced inflammatory profile, better anemia correction and prevention of β₂-microglobulin-associated amyloidosis). Recently, several cohort studies have shown that hemodiafiltration with high substitution volume was associated with a significant reduction in mortality. Randomized studies have been conducted in Europe to confirm these facts. The high safety of online hemodiafiltration has been confirmed in clinical practice by prospective studies. Online hemodiafiltration has reached its full maturity phase and is expected to represent the new standard of renal replacement therapy.

Is Hemodialysis Patient Survival Dependent upon Small Solute Clearance (Kt/V)?: If So How Can Kt/V be Adjusted to Prevent Under Dialysis in Vulnerable Groups?

Small solute clearance achieved during a single hemodialysis session has been traditionally evaluated by urea clearance, normalized for total body water (Kt/Vurea) for more than 30 years. By consensus, the target sessional KtVurea for thrice weekly treatments has been increased from 0.9 to 1.2 over the years. Although this is supported by observational studies, there is a fundamental lack of prospective studies to support this threshold target. In clinical practice achieving sessional Kt/Vurea targets are most closely followed in the US. Yet there appears to be a paradox in that by following Kt/Vurea targets in the US hemodialysis patient survival is better for men and the obese, the opposite of what is seen in the general population. Delivery of a lower dose of hemodialysis to women and smaller men can be explained by underestimation of total body water. The advent of bioimpedance techniques which can measure both body water and body composition will potentially allow a rescaling and re-evaluation of the importance of small solute clearances (Kt/Vurea) in the hemodialysis patient population.

The influence of mortality rate from membrane flux for end-stage renal disease: A meta-analysis

To evaluate the influence of the high-flux hemodialysis (HFHD) and the low-flux hemodialysis (LFHD) on mortality rate for end-stage renal disease (ESRD). Four electronic databases including PubMed, EMBASE, the Cochrane Library, and ClinicalTrails were searched to identify relevant randomized clinical trials up to 31 August 2015. Seven studies enrolling a total of 4412 patients were included in this meta-analysis. For all-cause mortality comparing with LFHD, the result showed that there were significant difference (RR=0.75; 95% CI [0.60-0.94]; I²=84%; P<0.00001). For death due to infection comparing with LFHD, the result showed that there was no significant difference (RR=0.92; 95% CI [0.75-1.13]; I²=0%; P=0.86). For cardiovascular mortality, the overall meta-analysis result showed that there was a significant difference between the HFHD versus the LFHD (RR=0.75; 95% CI [0.60-0.94]; I²=55%; P=0.11). Publication bias was not detected by funnel plot. Based on these results, our study suggests that the HFHD has superior effectiveness over LFHD for long-term survival in ESRD.

Comparative Effectiveness of Dialyzers: A Longitudinal, Propensity Score-Matched Study of Incident Hemodialysis Patients

Supplemental Digital Content is available in the text.

Differences in dialyzer design may have consequences for patient outcomes. We evaluated the comparative effectiveness of commonly used dialyzers with respect to measures of dialysis treatment, anemia management, inflammation, and dialyzer clotting. Patients receiving hemodialysis between January 1, 2009, and December 31, 2013, and using polyarylethersulfone–polyvinylpyrrolidone (PAS-PVP; Polyflux Revaclear) or polysulfone (PS; Optiflux 160 or Optiflux 180) dialyzers were followed for 1 year or until end of study or censoring for dialyzer switch, modality change, or loss to follow-up. For each comparison, eligible patients were propensity score-matched 1:1 on a range of baseline characteristics. Outcomes were assessed using generalized linear mixed models. Dialysis adequacy was similar in both dialyzer groups. Erythropoiesis-stimulating agent (ESA) doses were lower for patients using PAS-PVP versus patients using PS-160 (difference range: 75–589 units/treatment; statistically significant in months 1–5 and 7) and for patients using PAS-PVP versus patients using PS-180 (difference range: 27–591 unit/treatment; statistically significant in months 1–9). Intravenous iron doses trended lower for patients using PAS-PVP versus patients using PS, but hemoglobin concentrations were equivalent. In conclusion, use of PAS-PVP versus PS dialyzers was associated with equivalent dialysis adequacy, lower ESA doses, modestly lower Intravenous iron doses, and equivalent hemoglobin concentrations.

Prognostic effect of high-flux hemodialysis in patients with chronic kidney disease

We investigated the prognostic effects of high-flux hemodialysis (HFHD) and low-flux hemodialysis (LFHD) in patients with chronic kidney disease (CKD). Both an electronic and a manual search were performed based on our rigorous inclusion and exclusion criteria to retrieve high-quality, relevant clinical studies from various scientific literature databases. Comprehensive meta-analysis 2.0 (CMA 2.0) was used for the quantitative analysis. We initially retrieved 227 studies from the database search. Following a multi-step screening process, eight high-quality studies were selected for our meta-analysis. These eight studies included 4967 patients with CKD (2416 patients in the HFHD group, 2551 patients in the LFHD group). The results of our meta-analysis showed that the all-cause death rate in the HFHD group was significantly lower than that in the LFHD group (OR=0.704, 95%CI=0.533-0.929, P=0.013). Additionally, the cardiovascular death rate in the HFHD group was significantly lower than that in the LFHD group (OR=0.731, 95%CI=0.616-0.866, P<0.001). The results of this meta-analysis clearly showed that HFHD decreases all-cause death and cardiovascular death rates in patients with CKD and that HFHD can therefore be implemented as one of the first therapy choices for CKD.

Dialyzer Reuse and Outcomes of High Flux Dialysis

Background

The bulk of randomized trial evidence for the expanding use of High Flux (HF) hemodialysis worldwide comes from two randomized controlled trials, one of which (HEMODIALYSIS, HEMO) allowed, while the other (Membrane Outcomes Permeability, MPO) excluded, the reuse of membranes. It is not known whether dialyzer reuse has a differential impact on outcomes with HF vs low flyx (LF) dialyzers.

Methods

Proportional Hazards Models and Joint Models for longitudinal measures and survival outcomes were used in HEMO to analyze the relationship between β2-microglobulin (β2M) concentration, flux, and reuse. Meta-analysis and regression techniques were used to synthesize the evidence for HF dialysis from HEMO and MPO.

Findings

In HEMO, minimally reused (< 6 times) HF dialyzers were associated with a hazard ratio (HR) of 0.67 (95% confidence interval, 95%CI: 0.48–0.92, p = 0.015), 0.64 (95%CI: 0.44 – 0.95, p = 0.03), 0.61 (95%CI: 0.41 – 0.90, p = 0.012), 0.53 (95%CI: 0.28 – 1.02, p = 0.057) relative to minimally reused LF ones for all cause, cardiovascular, cardiac and infectious mortality respectively. These relationships reversed for extensively reused membranes (p for interaction between reuse and flux < 0.001, p = 0.005) for death from all cause and cardiovascular causes, while similar trends were noted for cardiac and infectious mortality (p of interaction between reuse and flux of 0.10 and 0.08 respectively). Reduction of β2M explained only 1/3 of the effect of minimally reused HF dialyzers on all cause mortality, while non-β2M related factors explained the apparent attenuation of the benefit with more extensively reused dialyzers. Meta-regression of HEMO and MPO estimated an adjusted HR of 0.63 (95% CI: 0.51–0.78) for non-reused HF dialyzers compared with non-reused LF membranes.

Conclusions

This secondary analysis and synthesis of two large hemodialysis trials supports the widespread use of HF dialyzers in clinical hemodialysis over the last decade. A mechanistic understanding of the effects of HF dialysis and the reuse process on dialyzers may suggest novel biomarkers for uremic toxicity and may accelerate membrane technology innovations that will improve patient outcomes.

The impact of high-flux dialysis on mortality rates in incident and prevalent hemodialysis patients

BACKGROUND/AIMS

The effect of high-flux (HF) dialysis on mortality rates could vary with the duration of dialysis. We evaluated the effects of HF dialysis on mortality rates in incident and prevalent hemodialysis (HD) patients.

METHODS

Incident and prevalent HD patients were selected from the Clinical Research Center registry for end-stage renal disease (ESRD), a Korean prospective observational cohort study. Incident HD patients were defined as newly diagnosed ESRD patients initiating HD. Prevalent HD patients were defined as patients who had been receiving HD for > 3 months. The primary outcome measure was all-cause mortality.

RESULTS

This study included 1,165 incident and 1,641 prevalent HD patients. Following a median 24 months of follow-up, the mortality rates of the HF and low-flux (LF) groups did not significantly differ in the incident patients (hazard ratio [HR], 1.046; 95% confidence interval [CI], 0.592 to 1.847; p = 0.878). In the prevalent patients, HF dialysis was associated with decreased mortality compared with LF dialysis (HR, 0.606; 95% CI, 0.416 to 0.885; p = 0.009).

CONCLUSIONS

HF dialysis was associated with a decreased mortality rate in prevalent HD patients, but not in incident HD patients.

Comparison of the impact of high-flux dialysis on mortality in hemodialysis patients with and without residual renal function

Background

The effect of flux membranes on mortality in hemodialysis (HD) patients is controversial. Residual renal function (RRF) has shown to not only be as a predictor of mortality but also a contributor to β2-microglobulin clearance in HD patients. Our study aimed to determine the interaction of residual renal function with dialyzer membrane flux on mortality in HD patients.

Methods

HD Patients were included from the Clinical Research Center registry for End Stage Renal Disease, a prospective observational cohort study in Korea. Cox proportional hazards regression models were used to study the association between use of high-flux dialysis membranes and all-cause mortality with RRF and without RRF. The primary outcome was all-cause mortality.

Results

This study included 893 patients with 24 h-residual urine volume ≥100 ml (569 and 324 dialyzed using low-flux and high-flux dialysis membranes, respectively) and 913 patients with 24 h-residual urine volume <100 ml (570 and 343 dialyzed using low-flux and high-flux dialysis membranes, respectively). After a median follow-up period of 31 months, mortality was not significantly different between the high and low-flux groups in patients with 24 h-residual urine volume ≥100 ml (HR 0.86, 95% CI, 0.38–1.95, P = 0.723). In patients with 24 h-residual urine volume <100 ml, HD using high-flux dialysis membrane was associated with decreased mortality compared to HD using low-flux dialysis membrane in multivariate analysis (HR 0.40, 95% CI, 0.21–0.78, P = 0.007).

Conclusions

Our data showed that HD using high-flux dialysis membranes had a survival benefit in patients with 24 h-residual urine volume <100 ml, but not in patients with 24 h-residual urine volume ≥100 ml. These findings suggest that high-flux dialysis rather than low-flux dialysis might be considered in HD patients without RRF.

The impact of membrane permeability and dialysate purity on cardiovascular outcomes

The effects of high-flux dialysis and ultrapure dialysate on survival of hemodialysis patients are incompletely understood. We conducted a randomized controlled trial to investigate the effects of both membrane permeability and dialysate purity on cardiovascular outcomes. We randomly assigned 704 patients on three times per week hemodialysis to either high- or low-flux dialyzers and either ultrapure or standard dialysate using a two-by-two factorial design. The primary outcome was a composite of fatal and nonfatal cardiovascular events during a minimum 3 years follow-up. We did not detect statistically significant differences in the primary outcome between high- and low-flux (HR=0.73, 95% CI=0.49 to 1.08, P=0.12) and between ultrapure and standard dialysate (HR=0.90, 95% CI=0.61 to 1.32, P=0.60). Posthoc analyses suggested that cardiovascular event-free survival was significantly better in the high-flux group compared with the low-flux group for the subgroup with arteriovenous fistulas, which constituted 82% of the study population (adjusted HR=0.61, 95% CI=0.38 to 0.97, P=0.03). Furthermore, high-flux dialysis associated with a lower risk for cardiovascular events among diabetic subjects (adjusted HR=0.49, 95% CI=0.25 to 0.94, P=0.03), and ultrapure dialysate associated with a lower risk for cardiovascular events among subjects with more than 3 years of dialysis (adjusted HR=0.55, 95% CI=0.31 to 0.97, P=0.04). In conclusion, this trial did not detect a difference in cardiovascular event-free survival between flux and dialysate groups. Posthoc analyses suggest that high-flux hemodialysis may benefit patients with an arteriovenous fistula and patients with diabetes and that ultrapure dialysate may benefit patients with longer dialysis vintage.

Dialyzer reuse and mortality risk in patients with end-stage renal disease: a systematic review

BACKGROUND AND AIM

Robust evidence about dialyzer reuse effects on mortality is not available. Our aim was to summarize the evidence for the effectiveness of dialyzer reuse compared to single use in patients with end-stage renal disease.

METHODS

We searched MEDLINE, Embase, CINAHL, SciELO, LILACS, USRDS ADR, universities' theses databases and annals of congress from major nephrology societies. Reviewers performed the study selection and data extraction independently. We used the GRADE approach to assess the quality of the evidence. Mortality was the primary outcome.

RESULTS

A total of 1,190 studies were retrieved, and 14 were included in the review (n = 956,807 patients). The disinfectants used on dialyzer reprocessing were hypochlorite, formaldehyde, glutaraldehyde, and peracetic acid. The evidence available from the studies was of very low quality. Most studies found no differences between groups. In studies with statistically significant differences, these differences were not observed in all groups and they varied by the type of disinfectant, time of observation and treatment unit.

CONCLUSIONS

No significant differences were identified for the superiority or inferiority of dialyzer reuse versus single use when assessing the mortality of patients with end-stage renal disease. Studies of higher quality, including randomized clinical trials, are required to provide conclusive evidence regarding the effectiveness and safety of dialyzer reuse.

Differences in bio-incompatibility among four biocompatible dialyzer membranes using in maintenance hemodialysis patients

BACKGROUND

Following the introduction of modified cellulosic and then synthetic membrane dialyzers, it was realized that the dialyzer bio-incompatibility depends on the membrane composition. We designed a prospective, randomized, cohort study of 6 months to determine several parameters of biocompatibility in maintenance hemodialysis (MHD) patients treated with four different membrane dialyzers.

METHODS

There were 60 MHD patients enrolled in the study. In baseline, synthetic low-flux dialyzer, polysulfone (PS) membrane was used in all patients for at least 3 months. Then the patients were randomly divided into three groups according to different dialyzer membranes. Synthetic high-flux dialyzer group, polyethersulfone membrane, cellulose triacetate (CTA) high-flux membrane, and synthetic low-flux dialyzer, polymethylmethacrylate (PMMA) membrane were used in 6 months. A new dialyzer was used for each study treatment, and there was no dialyzer reuse. The biocompatibility markers and solutes removal markers were detected repeatedly at different time points.

RESULTS

The blood levels of highly sensitive C reactive protein, interleukin (IL)-1β, and interleukin (IL)-13 showed no difference among different groups at al time points. However, the blood complement levels and white blood cell counts were significantly different among three groups. When the dialyzers changed from PS to PMMA membrane, C3a levels and white blood cell counts changed significantly (p < 0.05). Moreover, the changes of C5a levels were significantly different between group CTA and group PMMA in month 3 (p < 0.05).

CONCLUSION

There were much more differences on bio-incompatibility among different dialyzer membranes.

Symmetric dimethylarginine as a proinflammatory agent in chronic kidney disease

BACKGROUND & OBJECTIVES

Chronic kidney disease (CKD) is characterized by chronic inflammation, considered a nontraditional risk factor for cardiovascular disease, the major cause of death in CKD. Symmetric dimethylarginine (SDMA) was recently demonstrated to induce reactive oxygen species in monocytes. The present study further investigates the inflammatory character of SDMA compared with its structural counterpart asymmetric dimethylarginine (ADMA).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In vitro, the effect of SDMA on intracellular monocytic expression of IL-6 and TNF-α was studied followed by an evaluation of nuclear factor (NF)-κB activation. Additionally, an association of SDMA with inflammatory parameters in consecutive stages of CKD was evaluated in vivo.

RESULTS

Monocytes incubated with SDMA showed increased IL-6 and TNF-α expression and a rise in active NF-κB. N-acetylcysteine abrogated both these effects. No significant effects were observed with ADMA. In vivo, 142 patients (67 ± 12 years) at different stages of CKD showed an inverse association between serum SDMA and ADMA and renal function. Correlations between SDMA and IL-6, TNF-α, and albumin were more significant than for ADMA, while multiple regression analysis only retained TNF-α at a high significance for SDMA (P < 0.0001). In receiver operating characteristic analysis for inflammation, defined as an IL-6 level above 2.97 pg/ml (median), the discriminative power of SDMA (area under the curve [AUC]: 0.69 ± 0.05) directly followed that of C-reactive protein (AUC: 0.82 ± 0.04) and albumin (AUC: 0.72 ± 0.05; for all, P < 0.0001) and preceded that of ADMA (P = 0.002).

CONCLUSIONS

The present study shows that SDMA is involved in the inflammatory process of CKD, activating NF-κB and resulting in enhanced expression of IL-6 and TNF-α, which is corroborated by the clinical data pointing to an in vivo association of SDMA with inflammatory markers in CKD at different stages.

The influence of hemodialysis membrane permeability on serum paraoxonase-1 activity and oxidative status parameters

We aimed to measure oxidative stress parameters and paraoxonase-1 (PON-1) enzyme activities in chronic hemodialysis (HD) patients and to investigate whether HD membrane permeability has any influence on those measures. Forty-seven HD patients and 24 controls were enrolled. At the first step of the study, all HD patients had undergone HD treatment via "low-flux" membranes for 4 weeks. At the second step of the study, the membranes were switched to "high-flux" membranes and HD treatments were also performed via "high-flux" membranes for 4 weeks. Blood samples were withdrawn after completion of 4 weeks treatment for each membrane. Total oxidant status (TOS), total antioxidant status (TAS), and paraoxonase and arylesterase activities were measured in blood samples of the patients and the controls. TOS and oxidative stress index (OSI) of both membranes were higher than controls (all, P < 0.05), while TAS and paraoxonase and arylesterase activities were lower (all P < 0.05). Paraoxonase (P < 0.05, r = -0.437 and P < 0.05, r = -0.453, respectively) and arylesterase (P < 0.05, r = -0.333 and P < 0.05, r = -0.371, respectively) activities of "low-flux" and "high-flux" membranes were inversely correlated with OSI. There were no significant differences between "low-flux" and "high-flux" membranes in regard to oxidative stress parameters or PON-1 enzyme activities (all, P > 0.05). HD patients have increased oxidative stress and decreased serum PON-1 activities inversely correlated with oxidative stress. Membrane permeability seems to have no influence on oxidative stress parameters and PON-1 enzyme activities.

Do clinical outcomes in chronic hemodialysis depend on the choice of a dialyzer?

Nephrologists are presented with a range of choices when selecting a dialyzer for chronic hemodialysis. Dialyzers differ in the material, structure, permeability and surface area of their membrane, and how the dialyzer is sterilized. Opinions vary regarding the impact of dialyzer characteristics on patient outcomes and which, if any, of these properties to take into account when choosing a dialyzer can be confusing. In the general dialysis population, there is no compelling evidence that the choice of a membrane material from among those materials currently in clinical use has a significant impact on morbidity or mortality (although there are rare patients who will react adversely to a given dialysis membrane). Similarly, most dialyzers are capable of adequately removing small solutes, such as urea, provided they are used with an appropriate blood flow rate and treatment time to ensure delivery of a single-pool Kt/V(urea) of at least 1.25 for men and 1.65 for women. However, in some dialysis patient subpopulations, the results of randomized clinical trials suggest that use of dialyzer containing high-flux membranes confers an outcome advantage. The extent to which this advantage is realized might also depend on how the dialyzer is used, with application in convective therapies such as hemodiafiltration being superior to diffusive therapies such as hemodialysis. This possibility is currently the subject of several large clinical trials.

High-flux dialyzers, backfiltration, and dialysis fluid quality

Currently, high-flux hemodialysis is the most common mode of dialysis therapy worldwide. Its steadily increasing use is largely based on the desire to reduce the excessively high morbidity and mortality of end-stage renal disease patients maintained on conventional dialysis (low-flux, mostly cellulosic membranes) by offering better biocompatibility and enhanced removal of uremic toxins. Two large randomized trials suggest a survival benefit for selected subgroups of high-flux dialysis patients such as diabetics, patients with hypoalbuminemia, or patients who have been on dialysis for a long period (>3.7 years). The major disadvantage of high-flux hemodialysis relates to the use of dialysis fluid, which is commonly not pure and may endanger patients treated with high-flux hemodialysis. Endotoxin fragments and other bacterial substances derived from bacteriologically contaminated dialysis fluid may, even at bacterial counts or endotoxin concentrations within the limits of accepted standards of dialysis fluid purity, enter from the dialysate into the patient's blood either by convective transfer (backfiltration) or by movement down the concentration gradient (backdiffusion). Repeated exposure of high-flux hemodialysis patients to backtransport of dialysate contaminants aggravates the uremia-associated inflammatory response syndrome and contributes to long-term morbidity. At present, the only solution to circumvent the risks of backtransport is the use of dry powder cartridges for bicarbonate concentrate and the use of bacteria- and endotoxin-retentive filters for the online production of ultrapure dialysis fluid. Use of ultrapure dialysis fluid (bacteria <0.1 CFU/ml and endotoxin <0.03 IU/ml) has been found to reduce inflammation and comorbidities in clinical investigations compared to commercial dialysis fluid. The European Renal Association and a number of national societies in Europe or in Japan strongly recommend the use of ultrapure dialysis for high-flux hemodialysis.

Endothelial progenitor cells in patients on extracorporeal maintenance dialysis therapy

BACKGROUND

Chronic renal failure patients have a high cardiovascular disease burden, low numbers and impaired function of endothelial progenitor cells (EPCs). We hypothesized that enhanced uraemic toxin removal restores EPCs in haemodialysis patients.

METHODS

In a prospective, randomized, cross-over trial, 18 patients were subjected to 4 weeks of each low-flux haemodialysis, high-flux haemodialysis and haemodiafiltration differing in uraemic toxin removal. EPCs were determined at baseline and at the end of each 4-week period. A cohort of 16 healthy volunteers served as control. EPCs were studied after culture on fibronectin (CFU-Hill) and collagen-1 (ECFC).

RESULTS

Dialysis patients had a lower number of ECFCs than in healthy controls (P < 0.001) and a reduced fraction of vital ECFCs (P < 0.05), whereas the formation of endothelial cell colonies (ECCs) was increased (P < 0.05). Different middle molecular uraemic toxin removal had no effects on EPC numbers. The number of prototypical EPCs (CD34( +)/VEGFR2-KDR( +)/CD45( -) ECFCs) was similar between patients and controls. Correlations of plasma C-reactive protein with ECC count, CFU-Hill colony count and CD34( +)/VEGFR2-KDR( +)/CD45( -) subpopulation of both ECFC and CFU-Hill cells were observed.

CONCLUSIONS

Different middle molecule removal has no effect on EPCs. Reduced vitality and enhanced ECC formation suggest growth induction of impaired EPCs in chronic renal failure and are associated with inflammation.

The impact of beta2-microglobulin clearance on the risk factors of cardiovascular disease in hemodialysis patients

beta2-Microglobulin (beta2M) is an independent predictor of outcome for hemodialysis (HD) patients and a representative substance of middle molecules. We tested the relationship among serum beta2M levels and cardiovascular disease (CVD) risk factors in HD patients. A total of 132 HD patients were divided according to the dialysis membrane used [property; cellulose and synthetic or beta2M clearance; low filtration (LF), middle filtration (MF), and high filtration (HF)]. There was no significant difference in CVD risk factors between cellulose and synthetic groups. On the other hand, serum beta2M, highly-sensitive C-reactive protein (hCRP), troponin-T (TnT), and myeloperoxidase (MPO) levels of LF were significantly higher and those of prealbumin (PA) were lower than the MF and HF. Serum beta2M level was positively correlated with hCRP, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), MPO, TnT, N-terminal pro-B-type natriuretic peptide (NT-proBNP) and inversely correlated with PA and ankle-brachial index (ABI). There was a significant correlation between serum beta2M levels and various CVD risk factors in HD. Cardiovascular disease risk factors in HD patients were dependent on the beta2M clearance but not membrane property.

Novel Trends in Haemodialysis: Where Are We Heading?

The mortality and morbidity of end-stage renal failure patients undergoing conventional thrice weekly in-centre haemodialysis remain alarmingly high despite continuing advances in haemodialysis technologies and improvements in clinical care. Home haemodialysis continues to be under-utilised in many parts of the world despite the reported benefits. Alternative haemodialysis regimens including longer and/or more frequent dialysis (e.g. nocturnal haemodialysis and short daily haemodialysis), haemodiafiltration and the use of high flux dialysers have become more widespread in recent years as nephrologists struggle to improve the dismal survival figures. Whilst most of the encouraging data have come from observational studies, many randomised controlled trials which will provide more robust data are already underway. This review aims to provide a concise update of the recent and novel trends in haemodialysis. Key words: Haemodiafiltration, High flux dialysis, Home haemodialysis, Nocturnal haemodialysis, Short daily haemodialysis

Effect of different synthetic membranes on laboratory parameters and survival in chronic haemodialysis patients

Background. A number of studies suggested that the type of dialysis membrane is associated with differences in long-term outcome of patients undergoing haemodialysis, both in terms of morbidity and mortality. In the majority of dialysis units, synthetic membranes are being used. However, no studies are available so far for comparison between different biocompatible membranes. Therefore, we studied the influence of high- and low-flux polysulphone membranes (PS) in comparison with polymethylmethacrylate (PMMA) membranes on mortality and morbidity on the basis of various laboratory parameters. Methods. In a cohort study, data of 260 consecutive haemodialysis patients entering our dialysis unit in the years 2003-07 were collected, comparing 435 PS patient-years and 85 PMMA patient-years. PMMA membranes (n = 33) were used for those patients who did not tolerate (e.g. for pruritus) PS membranes (n = 227). Low-flux dialysers (n = 233) were compared with high-flux (n = 37). Laboratory values were evaluated by unpaired t-test, and mortality was evaluated by log-rank test and Cox regression analysis adjusted for age, diabetes and laboratory parameters. Results. Patients in our dialysis unit had a high cardiovascular risk as demonstrated by a proportion of 63% of peripheral arterial disease. Despite this, cumulative survival was almost 60% after 5 years on dialysis. It was slightly but not significantly higher in patients on PMMA (68%) compared with PS dialysers (54%) and on high-flux (61%) versus low-flux membranes (54%). After accounting for the confounding effect of age and diabetes in the multivariate Cox regression analysis, there was no impact of the membranes used (high- or low-flux, PMMA or PS) on survival. Only age at the onset of dialysis showed a significant influence on survival (P ≤ 0.001). Independent predictors of mortality in all patients in the multivariate Cox regression analysis were age, haemoglobin, leucocytes, C-reactive protein (CRP) and creatinine. Laboratory parameters between the high- and low- flux groups were not different. PS-treated patients showed significantly (P ≤ 0.05) higher values for leucocytes, thrombocytes, ferritin, and CRP and lower values for haemoglobin, transferrin, creatinine, uric acid, creatine kinase (CK), and sodium than PMMA-treated patients. Irrespective of the membrane used, in deceased patients, the following laboratory values were higher than for patients alive: leucocytes, thrombocytes, ferritin and CRP; the following were lower: haemoglobin, iron, total protein, urea, creatinine, uric acid and CK. Conclusions. The data of 260 severely ill haemodialysis patients showed a slightly, but not significantly, reduced mortality in patients treated with PMMA membranes in comparison with PS and with high-flux membranes compared with low-flux. High- or low-flux membranes exhibited no difference in laboratory values. However, in PMMA patients, laboratory data with respect to inflammation, anaemia and nutrition were significantly improved compared with the PS group. A similarly positive laboratory pattern was seen in patients alive compared with patients deceased with both membrane types. The favourable effect of PMMA membranes may be explained by the reduced activation of catabolic components and inflammation, which, in turn, would result in an improved nutrition and better response to recombinant human erythropoietin.

Did 20 years of technological innovations in hemodialysis contribute to better patient outcomes?

During the past two decades, impressive technological innovations have been introduced in the field of hemodialysis. This review analyzes whether these have been translated into better patient survival. The potential impacts of an increase in dialysis dosage, the preference of high-flux versus low-flux membranes, the choice between convection and diffusion as dialysis strategy, the chemical composition and biologic purity of dialysate, the effect of sodium, potassium, volume profiling, and the intradialytic volume monitoring aiming at improving hemodynamic stability are explored. Studies in which the dialysis dosage was increased were not associated with increased patient survival, whereas the superiority of high-flux over low-flux membranes is not convincingly demonstrated. Although strict evidence is lacking, observational data suggest an advantage of convective over pure diffusive strategies. Longer duration of the dialysis sessions and/or higher frequency of dialysis is probably beneficial, but the results of powerful randomized, controlled trials should be awaited. Sodium profiling has more disadvantages than advantages, whereas potassium profiling mainly in arrhythmia-prone patients with ventricular hypertrophy should be considered. Intradialytic blood volume monitoring has reduced intradialytic hypotension episodes, but hard evidence for improving patient survival is lacking. Overall, the major technological advances in dialysis have not yet been translated into longer patient survival. Optimal predialysis care in preventing the cardiovascular damage that accumulates before the start of dialysis and timely creation of an arteriovenous fistula as vascular access is a more effective and more economic strategy in the long-term outcome of the dialysis patient.

Association between N-terminal pro-brain natriuretic peptide and acute ischemic stroke in patients on chronic hemodialysis

BACKGROUND

Plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) has been reported as a predictor for ischemic stroke in general population. However, predictive value of plasma NT-proBNP for acute ischemic stroke in patients on chronic hemodialysis has not been well established. The aim of this study was to determine whether NT-proBNP could predict acute ischemic stroke in patients on chronic hemodialysis.

METHODS

This study was designed prospectively. Clinical, laboratory, and echocardiographic variables were assessed in 72 patients on chronic hemodialysis. The plasma levels of NT-proBNP were measured by immunoassay.

RESULTS

During the follow-up period of 45 months, 11 patients had an acute ischemic stroke. The Kaplan-Meier plot showed an increased frequency of acute ischemic stroke in patients with plasma levels of NT-proBNP above the median values compared to patients with lower concentrations (P = 0.028). The multivariate Cox proportional hazard models showed that the NT-proBNP was a significant independent predictor of acute ischemic stroke after adjustment for age, sex, mean blood pressure, diabetes, serum cholesterol levels, left ventricular mass index, and left ventricular fractional shortening (HR 6.66, 95% CI, 1.22-36.48, P = 0.029).

CONCLUSIONS

Our data suggest that plasma NT-proBNP levels predict the risk of acute ischemic stroke in patients on chronic hemodialysis.

Can convective therapies improve dialysis outcomes?

PURPOSE OF REVIEW

Convective treatments are characterized by enhanced removal of middle and large molecular weight solutes, important in the genesis of many complications of hemodialysis, compared with conventional low-flux hemodialysis. The availability of these techniques represented an intriguing innovation and a possible means to improve the still poor prognosis of hemodialysis patients. In this study we will critically review the most important published studies evaluating the impact of convective treatments on dialysis outcomes.

RECENT FINDINGS

The Hemodialysis (HEMO) study showed that greater urea removal nonsignificantly reduces the relative risk of mortality and that also high-flux hemodialysis was associated with a nonsignificant reduction, although a secondary analysis pointed to an advantage for high-flux membranes in subgroups of patients. More recently, the Membrane Permeability Outcome (MPO) study found that survival could be improved by use of high-flux membranes compared with low-flux dialysis in high-risk patients as identified by serum albumin < or =4 g/dl as well as in people with diabetes. In an observational study, hemodiafiltration with large reinfusion volume has been associated with a lower relative risk of mortality, compared with low-flux hemodialysis.

SUMMARY

The biologic plausibility of advantages of convective treatments and the results of the MPO and Dialysis Outcomes and Practice Patterns (DOPPS) studies are supporting rationales for the use of convective treatments to improve survival and delay long-term complications of hemodialysis patients.

Effect of membrane permeability on survival of hemodialysis patients

The effect of high-flux hemodialysis membranes on patient survival has not been unequivocally determined. In this prospective, randomized clinical trial, we enrolled 738 incident hemodialysis patients, stratified them by serum albumin < or = 4 and >4 g/dl, and assigned them to either low-flux or high-flux membranes. We followed patients for 3 to 7.5 yr. Kaplan-Meier survival analysis showed no significant difference between high-flux and low-flux membranes, and a Cox proportional hazards model concurred. Patients with serum albumin < or = 4 g/dl had significantly higher survival rates in the high-flux group compared with the low-flux group (P = 0.032). In addition, a secondary analysis revealed that high-flux membranes may significantly improve survival of patients with diabetes. Among those with serum albumin < or = 4 g/dl, slightly different effects among patients with and without diabetes suggested a potential interaction between diabetes status and low serum albumin in the reduction of risk conferred by high-flux membranes. In summary, we did not detect a significant survival benefit with either high-flux or low-flux membranes in the population overall, but the use of high-flux membranes conferred a significant survival benefit among patients with serum albumin < or = 4 g/dl. The apparent survival benefit among patients who have diabetes and are treated with high-flux membranes requires confirmation given the post hoc nature of our analysis.

Role of symmetric dimethylarginine in vascular damage by increasing ROS via store-operated calcium influx in monocytes

BACKGROUND

The guanidines asymmetric dimethylarginine (ADMA), a marker of endothelial dysfunction, and its counterpart symmetric dimethylarginine (SDMA), considered inert, are accumulated in chronic kidney disease (CKD). The present study evaluates their effect on monocyte function, since previous data demonstrated leukocyte activation by other guanidino compounds.

METHODS

The effect of ADMA and SDMA on reactive oxygen species (ROS) production in human whole blood at baseline and after N-formyl-methionine-leucine-phenylalanine (fMLP) stimulation was evaluated. By using the fluorescent probe Fluo3-AM, the role of changes in monocytic cytoplasmic calcium ([Ca2+]i) was studied. Thapsigargin, and removal followed by addition of extracellular Ca2+ (Ca2+(ex)), was used to investigate the contribution of store-operated Ca2+-channels (SOCs). SKF96365 was used as a selective inhibitor of the SOCs. A pharmacologic intervention with captopril, known to affect Ca2+ influx, was tested.

RESULTS

SDMA enhanced ROS production in fMLP-stimulated monocytes using heparinized blood, and this effect was abolished in EDTA-anticoagulated blood. In the presence of SDMA, an increased Ca2+ entry from the extracellular milieu resulted in an elevated amplitude of the peak [Ca2+]i change triggered by fMLP. None of these effects were seen with ADMA. Depletion of the intracellular stores with thapsigargin in the absence of Ca2+(ex), followed by re-addition of Ca2+(ex) triggered a significantly larger Ca2+ entry after SDMA treatment versus saline. This effect was prevented with SKF96365, as was the SDMA-enhanced oxidative burst after fMLP. Pre-incubation with captopril also reduced the increased ROS production seen with SDMA.

CONCLUSIONS

SDMA, a uraemic retention solute considered inert, stimulates ROS production of monocytes by acting on Ca2+ entry via SOCs. This pro-inflammatory effect may trigger vascular pathology and may be involved in altering the prevalence of cardiovascular disease in CKD.

A new synthetic dialyzer with advanced permselectivity for enhanced low-molecular weight protein removal

Optimizing solute removal at minimized albumin loss is a major goal of dialyzer engineering. In a prospective, randomized, crossover study on eight patients (age 63 +/- 14 years) on maintenance hemodialysis, the new Baxter Xenium 170 high-flux dialyzer (BX), which contains a 1.7-m(2) PUREMA H dialysis membrane, was compared with two widely used reference high-flux dialyzers currently available for hemodialysis in North America, the Fresenius Optiflux 180 NR (FO) and the Gambro Polyflux 170 H (GP). Solute removal and biocompatibility were assessed in hemodialysis for 240 min at blood and dialysate flow rates of 300 and 500 mL/min, respectively. Additional ex vivo experiments detecting the interleukin-1beta (IL-1b) generation in recirculated donor blood were performed to demonstrate the pyrogen retention properties of the dialyzers. The instantaneous plasma clearances were similar for the three dialyzers except for cystatin c (cysc), for which a lower clearance was measured with FO as compared with BX and GP after 30 and 180 min of hemodialysis. The reduction ratios (RRs) corrected for the hemoconcentration of beta(2)-microglobulin and cysc were lower in FO (44 +/- 9 and 35 +/- 9%, respectively) versus BX (62 +/- 6 and 59 +/- 7%, respectively) and GP (61 +/- 7 and 56 +/- 8%, respectively). The RRs of the cytokine tumor necrosis factor alpha and interleukin-6 were not different between the dialyzers. The albumin loss was <300 mg for all filters. No differences between the dialyzers were found in the biocompatibility parameters showing very low leukocyte and complement activation. The ex vivo recirculation experiments revealed a significantly higher IL-1b generation for GP (710 +/- 585 pg/mL) versus BX (317 +/- 211 pg/mL) and FO (151 +/- 38 pg/mL). BX is characterized by a steep solute sieving profile with high low-molecular weight protein removal at virtually no albumin loss and an excellent biocompatibility. This improved performance may be regarded as a contribution to optimal dialysis therapy.

Stroke in chronic renal failure

Chronic kidney diseases and cardiovascular diseases have several common risk factors like hypertension and diabetes. In chronic renal disease stroke risk is several times higher than in the average population. The combination of classical risk factors and those characteristic of chronic kidney disease might explain this increased risk. Among acute cerebrovascular diseases intracerebral hemorrhages are more frequent than in those with normal kidney function. The outcome of stroke is worse in chronic kidney disease. The treatment of stroke (thrombolysis, antiplatelet and anticoagulant treatment, statins, etc.) is an area of clinical research in this patient group. There are no reliable data on the application of thrombolysis in acute stroke in patients with chronic renal disease. Aspirin might be administered. Carefulness, individual considerations and lower doses might be appropriate when using other treatments. The condition of the kidney as well as other associated diseases should be considered during administration of antihypertensive and lipid lowering medications.

A bench to bedside view of uremic toxins

Reviewing the current picture of uremic toxicity reveals its complexity. Focusing on cardiovascular damage as a model of uremic effects resulting in substantial morbidity and mortality, most molecules with potential to affect the function of a variety of cell types within the vascular system are difficult to remove by dialysis. Examples are the larger middle molecular weight molecules and protein-bound molecules. Recent clinical studies suggest that enhancing the removal of these compounds is beneficial for survival. Future therapeutic options are discussed, including improved removal of toxins and the search for pharmacologic strategies blocking responsible pathophysiologic pathways.