Haemodiafiltration-optimal efficiency and safety

Hemodiafiltration for children with stage 5 chronic kidney disease: technical aspects and outcomes

Despite significant medical and technical improvements in the field of dialysis, the morbidity and mortality among patients with chronic kidney disease (CKD) stage 5 on dialysis remains extremely high. Hemodiafiltration (HDF), a dialysis method that combines the two main principles of hemodialysis (HD) and hemofiltration-diffusion and convection-has had a positive impact on survival when delivered with a high convective dose. Improved outcomes with HDF have been attributed to the following factors: HDF removes middle molecular weight uremic toxins including inflammatory cytokines, increases hemodynamic stability, and reduces inflammation and oxidative stress compared to conventional HD. Two randomized trials in adults have shown improved survival with HDF compared to high-flux HD. A large prospective cohort study in children has shown that HDF attenuated the progression of cardiovascular disease, improved bone turnover and growth, reduced inflammation, and improved blood pressure control compared to conventional HD. Importantly, children on HDF reported fewer headaches, dizziness, and cramps; had increased physical activity; and improved school attendance compared to those on HD. In this educational review, we discuss the technical aspects of HDF and results from pediatric studies, comparing outcomes on HDF vs. conventional HD. Convective volume, the cornerstone of treatment with HDF and a key determinant of outcomes in adult randomized trials, is discussed in detail, including the practical aspects of achieving an optimal convective volume.

Improved β2-Microglobulin and Phosphorous Removal with Expanded Hemodialysis and Online Hemodiafiltration versus High-Flux Hemodialysis: A Cross-Over Randomized Clinical Trial

INTRODUCTION

Expanded hemodialysis (HDx) is expected to provide enhanced permeability of medium-sized molecules, selective solute retention, and better internal retrofiltration. The primary objective of this study was to compare the efficiency for removal of β2-microglobulin with 3 different extracorporeal therapies (ETs): high-flux hemodialysis (HF), online hemodiafiltration (OL-HDF), and HDx. The secondary objective was to evaluate the efficiency of removal of other uremic toxins, including urea, phosphate, CRP, IL-6, IL-10, TNF-⍺, indoxyl sulfate, and p-cresol.

METHODS

This single-center, randomized, and cross-over study was performed. Patients were randomized to determine the initial modality of treatment, each period lasted 4 weeks and between one modality and another, there was a washout period of 1 week. Reduction ratios (RRs) of different-size molecules and albumin were calculated for the different ET.

RESULTS

Twenty-two patients were included, β2-microglobulin RR was greater during both OL-HDF and HDx as compared to HF (RR 62% vs. 73% vs. 27%, respectively, p = <0.0001), and there was no significant difference between HDx and OL-HDF (p = 0.09). A decrease in serum phosphate levels was observed in the HDx and OL-HDF periods, contrary to an increase in HF (-0.79 mg/dL vs. -1.02 mg/dL vs. + 0.11 mg/dL, respectively, p = <0.0001). There was no difference in RRs of other molecules (BUN, CRP, IL-6, IL-10, TNF-⍺, indoxyl sulfate, and p-Cresol). There was no decrease in serum albumin in any ET.

CONCLUSION

HDx provides enhanced removal of β2-microglobulin and phosphate as compared to HF, and similar efficacy as with OL-HDF. HDx should be considered an alternative to chronic convective therapies.

Performance Evaluation and Fouling Propensity of Forward Osmosis (FO) Membrane for Reuse of Spent Dialysate

The number of chronic renal disease patients has shown a significant increase in recent decades over the globe. Hemodialysis is the most commonly used treatment for renal replacement therapy (RRT) and dominates the global dialysis market. As one of the most water-consuming treatments in medical procedures, hemodialysis has room for improvement in reducing wastewater effluent. In this study, we investigated the technological feasibility of introducing the forward osmosis (FO) process for spent dialysate reuse. A 30 LMH of average water flux has been achieved using a commercial TFC membrane with high water permeability and salt removal. The water flux increased up to 23% with increasing flowrate from 100 mL/min to 500 mL/min. During 1 h spent dialysate treatment, the active layer facing feed solution (AL-FS) mode showed relatively higher flux stability with a 4–6 LMH of water flux reduction while the water flux decreased significantly at the active layer facing draw solution (AL-DS) mode with a 10–12 LMH reduction. In the pressure-assisted forward osmosis (PAFO) condition, high reverse salt flux was observed due to membrane deformation. During the membrane filtration process, scaling occurred due to the influence of polyvalent ions remaining on the membrane surface. Membrane fouling exacerbated the flux and was mainly caused by organic substances such as urea and creatinine. The results of this experiment provide an important basis for future research as a preliminary experiment for the introduction of the FO technique to hemodialysis.

Effects of Hemodiafiltration versus Conventional Hemodialysis in Children with ESKD: The HDF, Heart and Height Study

BACKGROUND

Hypertension and cardiovascular disease are common in children undergoing dialysis. Studies suggest that hemodiafiltration (HDF) may reduce cardiovascular mortality in adults, but data for children are scarce.

METHODS

The HDF, Heart and Height study is a nonrandomized observational study comparing outcomes on conventional hemodialysis (HD) versus postdilution online HDF in children. Primary outcome measures were annualized changes in carotid intima-media thickness (cIMT) SD score and height SD score.

RESULTS

We enrolled 190 children from 28 centers; 78 on HD and 55 on HDF completed 1-year follow-up. The groups were comparable for age, dialysis vintage, access type, dialysis frequency, blood flow, and residual renal function. At 1 year, cIMT SD score increased significantly in children on HD but remained static in the HDF cohort. On propensity score analysis, HD was associated with a +0.47 higher annualized cIMT SD score compared with HDF. Height SD score increased in HDF but remained static in HD. Mean arterial pressure SD score increased with HD only. Factors associated with higher cIMT and mean arterial pressure SD-scores were HD group, higher ultrafiltration rate, and higher β2-microglobulin. The HDF cohort had lower β2-microglobulin, parathyroid hormone, and high-sensitivity C-reactive protein at 1 year; fewer headaches, dizziness, or cramps; and shorter postdialysis recovery time.

CONCLUSIONS

HDF is associated with a lack of progression in vascular measures versus progression with HD, as well as an increase in height not seen in the HD cohort. Patient-related outcomes improved among children on HDF correlating with improved BP control and clearances. Confirmation through randomized trials is required.

In silico comparison of protein-bound uremic toxin removal by hemodialysis, hemodiafiltration, membrane adsorption, and binding competition

Protein-bound uremic toxins (PBUTs) are poorly removed during hemodialysis (HD) due to their low free (dialyzable) plasma concentration. We compared PBUT removal between HD, hemodiafiltration (HDF), membrane adsorption, and PBUT displacement in HD. The latter involves infusing a binding competitor pre-dialyzer, which competes with PBUTs for their albumin binding sites and increases their free fraction. We used a mathematical model of PBUT/displacer kinetics in dialysis comprising a three-compartment patient model, an arterial/venous tube segment model, and a dialyzer model. Compared to HD, improvements in removal of prototypical PBUTs indoxyl sulfate (initial concentration 100 µM, 7% free) and p-cresyl sulfate (150 µM, 5% free) were: 5.5% and 6.4%, respectively, for pre-dilution HDF with 20 L replacement fluid; 8.1% and 9.1% for post-dilution HDF 20 L; 15.6% and 18.3% for pre-dilution HDF 60 L; 19.4% and 22.2% for complete membrane adsorption; 35.0% and 41.9% for displacement with tryptophan (2000 mg in 500 mL saline); 26.7% and 32.4% for displacement with ibuprofen (800 mg in 200 mL saline). Prolonged (one-month) use of tryptophan reduces the IS and pCS time-averaged concentration by 28.1% and 29.9%, respectively, compared to conventional HD. We conclude that competitive binding can be a pragmatic approach for improving PBUT removal.

Middle molecule elimination in expanded haemodialysis: only convective transport?

Background

New high-retention onset dialysers have shown improved efficacy in the elimination of uraemic toxins, and their depurative capacity has been compared with high convective volumes of online haemodiafiltration. Haemodialysis (HD) using high-flux membranes leads to convective transport by internal filtration [direct filtration (DF)/backfiltration (BF)] and allows the removal of middle molecules (MMs). The aim of this study was to assess solute transport mechanisms in expanded HD (HDx).

Methods

In 14 4-h HDx sessions with Theranova-500 dialysers under similar dialysis conditions (blood flow 400 mL/min, dialysate flow 700 mL/min, dialysate temperature 35.5°C), pressures at the inlet and outlet of both dialyser compartments (P _bi, P _bo, P _di and P _do) were collected hourly to estimate DF/BF volumes by semi-empirical methods. Uraemic toxins with various molecular weights were measured pre-dialysis, at 1 h (pre-filter and post-filter) and post-dialysis to calculate molecules' reduction over time and dialyser in vivo clearances.

Results

Ultrafiltration was 1.47 ± 0.9 L and Kt/V 1.74 ± 0.3. Hydrodynamic data (P _bi: 259 ± 39, P _bo: 155 ± 27, P _di: 271 ± 30, P _do: 145 ± 29 mmHg and oncotic pressure 22.0 ± 3.5 mmHg) allowed the estimation of DF/BF rates. DF flow ranged from 29.5 ± 4.2 to 31.3 ± 3.9 mL/min and BF flow ranged from 25.1 ± 2.3 to 23.4 ± 2.6 mL/min. The highest calculated DF volume was 7506.8 ± 935.3 mL/session. Diffusive clearances (K _d) of all solutes were higher than their convective transport (all P < 0.001) except for prolactin (23 kDa) clearances, which showed no differences. Total clearances of all solutes were correlated with their K _d (ρ = 0.899-0.987, all P < 0.001) and Kt/V correlated with all reduction rates (ρ = 0.661-0.941, P = 0.010 to <0.001). DF flow was only associated with urea (ρ = -0.793, P = 0.001), creatinine (ρ = -0.675, P = 0.008) and myoglobin clearance (ρ = 0.653, P = 0.011).

Conclusion

Results suggest that diffusive transport is a main mechanism of MM elimination in HDx. HDx offers an efficient depuration of MM without the need for high convective volumes.

Effect of haemodiafiltration vs conventional haemodialysis on growth and cardiovascular outcomes in children - the HDF, heart and height (3H) study

BACKGROUND

Cardiovascular disease is prevalent in children on dialysis and accounts for almost 30% of all deaths. Randomised trials in adults suggest that haemodiafiltration (HDF) with high convection volumes is associated with reduced cardiovascular mortality compared to high-flux haemodialysis (HD); however paediatric data are scarce. We designed the haemodiafiltration, heart and height (3H) study to test the hypothesis that children on HDF have an improved cardiovascular risk profile, growth and nutritional status and quality of life, compared to those on conventional HD. We performed a non-randomised parallel-arm intervention study within the International Paediatric Haemodialysis Network Registry comparing children on HDF and conventional HD to determine annualised change in cardiovascular end-points and growth. Here we present the 3H study design and baseline characteristics of the study population.

METHODS

190 children were screened and 177 (106 on HD and 71 on HDF) recruited from 28 centres in 10 countries. There was no difference in age, underlying diagnosis, comorbidities, previous dialysis therapy, dialysis vintage, residual renal function, type of vascular access or blood flow between HD and HDF groups. High flux dialysers were used in 63% of HD patients and ultra-pure water was available in 52%. HDF patients achieved a median convection volume of 13.3 L/m²; this was associated with the blood flow rate only ((p = 0.0004, r = 0.42) and independent of access type (p = 0.38).

DISCUSSION

This is the largest study on dialysis outcomes in children that involves deep phenotyping across a wide range of cardiovascular, anthropometric, nutritional and health-related quality of life measures, to test the hypothesis that HDF leads to improved cardiovascular and growth outcomes compared to conventional HD.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02063776 . The trial was prospectively registered on the 14 Feb 2014.

Effect of Different Dialysis Methods on Cellular Immunity Function of Maintenance Haemodialysis Patients

Background

The study of the effect of different dialysis methods on cellular immune function of maintenance haemodialysis (MHD) patients should provide theoretical support for deciding on the best method of blood purification that effectively improves cellular immune function of haemodialysis patients.

Subjects and Method

Sixty MHD patients were randomly divided into three groups that respectively received treatment of haemodialysis (HD), high flux haemodialysis (HFHD) and haemodiafiltration (HDF). Peripheral blood T lymphocyte subsets [CD4+, CD8+, CD25+ (mIL-2R) and CD4+/CD8+ ratio] and serum interleukin (IL)-2 and soluble IL-2 receptor (sIL-2R) levels were detected before dialysis and 4, 24 and 48 hours after dialysis in all cases.

Results

Compared with the HD group, CD4+ and CD25+ cells, CD4+/CD8+ ratio and IL-2 level increased but sIL-2R level decreased in the HFHD and HDF groups at four hours without statistical significance (p > 0.05) and at 24 and 48 hours after dialysis with statistical significance (p < 0.05), while CD8+ cells had no change after dialysis (p > 0.05). Compared with the HFHD group, CD4+ and CD25+ cells, CD4+/CD8+ ratio, and IL-2 level increased but sIL-2R level decreased in the HDF group at four and 24 hours without statistical significance (p > 0.05) and at 48 hours after dialysis with statistical significance (p < 0.05), while CD8+ cells had no change after dialysis (p > 0.05).

Conclusion

The results indicate that HD can briefly improve the cellular immune function of MHD patients, while MHD and HFHD can improve it continuously, with HDF having the best effect.

Confronting Practical Problems for Initiation of On-line Hemodiafiltration Therapy

Conventional hemodialysis, which is based on the diffusive transport of solutes, is the most widely used renal replacement therapy. It effectively removes small solutes such as urea and corrects fluid, electrolyte and acid-base imbalance. However, solute diffusion coefficients decreased rapidly as molecular size increased. Because of this, middle and large molecules are not removed effectively and clinical problem such as dialysis amyloidosis might occur. Online hemodiafiltration which is combined by diffusive and convective therapies can overcome such problems by removing effectively middle and large solutes. Online hemodiafiltration is safe, very effective, economically affordable, improving session tolerance and may improve the mortality superior to high flux hemodialysis. However, there might be some potential limitations for setting up online hemodiafiltaration. In this article, we review the uremic toxins associated with dialysis, definition of hemodiafiltration, indication and prescription of hemodiafiltration and the limitations of setting up hemodiafiltration.

Removal of Dolutegravir by Hemodialysis in HIV-Infected Patients with End-Stage Renal Disease

Data on dolutegravir removal by hemodialysis are lacking. To study this, we measured dolutegravir plasma concentrations in samples of blood entering and leaving the dialyzer and of the resulting dialysate from 5 HIV-infected patients with end-stage renal disease. The median dolutegravir hemodialysis extraction ratio was 7%. The dolutegravir concentrations after the dialysis session remained far above the protein-binding-adjusted inhibitory concentration. Our results show minimal dolutegravir removal by hemodialysis, with no specific dolutegravir dosage adjustments required in this setting. (This study is registered at ClinicalTrials.gov under registration number NCT02487706.).

Uremic Toxicity of Advanced Glycation End Products in CKD

Advanced glycation end products (AGEs), a heterogeneous group of compounds formed by nonenzymatic glycation reactions between reducing sugars and amino acids, lipids, or DNA, are formed not only in the presence of hyperglycemia, but also in diseases associated with high levels of oxidative stress, such as CKD. In chronic renal failure, higher circulating AGE levels result from increased formation and decreased renal clearance. Interactions between AGEs and their receptors, including advanced glycation end product-specific receptor (RAGE), trigger various intracellular events, such as oxidative stress and inflammation, leading to cardiovascular complications. Although patients with CKD have a higher burden of cardiovascular disease, the relationship between AGEs and cardiovascular disease in patients with CKD is not fully characterized. In this paper, we review the various deleterious effects of AGEs in CKD that lead to cardiovascular complications and the role of these AGEs in diabetic nephropathy. We also discuss potential pharmacologic approaches to circumvent these deleterious effects by reducing exogenous and endogenous sources of AGEs, increasing the breakdown of existing AGEs, or inhibiting AGE-induced inflammation. Finally, we speculate on preventive and therapeutic strategies that focus on the AGE-RAGE axis to prevent vascular complications in patients with CKD.

High convection volume in online post-dilution haemodiafiltration: relevance, safety and costs

Increasing evidence suggests that treatment with online post-dilution haemodiafiltration (HDF) improves clinical outcome in patients with end-stage kidney disease, if compared with haemodialysis (HD). Although the primary analyses of three large randomized controlled trials (RCTs) showed inconclusive results, post hoc analyses of these and previous observational studies comparing online post-dilution HDF with HD showed that the risk of overall and cardiovascular mortality is lowest in patients who are treated with high-volume HDF. As such, the magnitude of the convection volume seems crucial and can be considered as the ‘dose’ of HDF. In this narrative review, the relevance of high convection volume in online post-dilution HDF is discussed. In addition, we briefly touch upon some safety and cost issues.

Optimization of the convection volume in online post-dilution haemodiafiltration: practical and technical issues

In post-dilution online haemodiafiltration (ol-HDF), a relationship has been demonstrated between the magnitude of the convection volume and survival. However, to achieve high convection volumes (>22 L per session) detailed notion of its determining factors is highly desirable. This manuscript summarizes practical problems and pitfalls that were encountered during the quest for high convection volumes. Specifically, it addresses issues such as type of vascular access, needles, blood flow rate, recirculation, filtration fraction, anticoagulation and dialysers. Finally, five of the main HDF systems in Europe are briefly described as far as HDF prescription and optimization of the convection volume is concerned.

High-efficiency on-line haemodiafiltration improves conduit artery endothelial function compared with high-flux haemodialysis in end-stage renal disease patients

BACKGROUND

Middle molecular weight uraemic toxins are considered to play an important role in vascular dysfunction and cardiovascular outcomes in end-stage renal disease (ESRD) patients. Recent dialysis techniques based on convection, specifically high-efficiency on-line haemodiafiltration (HDF), enhance the removal of middle molecular weight toxins and reduce all-cause mortality in haemodialysis (HD) patients. However, the mechanisms of these improved outcomes remain to be established.

METHODS

This prospective study randomly assigned 42 ESRD patients to switch from high-flux HD to high-efficiency on-line HDF (n=22) or to continue HD (n=20). Brachial artery endothelium-dependent flow-mediated dilatation, central pulse pressure, carotid artery intima-media thickness (IMT), internal diastolic diameter and distensibility and circulating markers of uraemia, inflammation and oxidative stress were blindly assessed before and after a 4-month follow-up.

RESULTS

Brachial flow-mediated dilatation and carotid artery distensibility increased significantly in the HDF group compared with HD, while carotid IMT and diameter remained similar. HDF decreased predialysis levels of the uraemic toxins β2-microglobulin, phosphate and blood TNFα mRNA expression. Oxidative stress markers were not different between the HD and HDF groups. Blood mRNA expression of protein kinase C β2, an endothelial NO-synthase (eNOS) inhibitor, decreased significantly with HDF.

CONCLUSIONS

High-efficiency on-line HDF prevents the endothelial dysfunction and stiffening of the conduit arteries in ESRD patients compared with high-flux HD. HDF decreases uraemic toxins, vascular inflammation, and is associated with subsequent improvement in eNOS functionality. These results suggest that reduced endothelial dysfunction may be an intermediate mechanism explaining the beneficial outcomes associated with HDF.

Hydration measurement by bioimpedance spectroscopy and blood pressure management in children on hemodialysis

BACKGROUND

Hypertension is frequent in chronic hemodialyzed patients and usually treated by reducing extracellular fluid. Probing dry weight only based on a clinical evaluation may be hazardous, especially in case of volume independent hypertension.

METHODS

We performed a 1-year retrospective study in three pediatric centers to define the relation between blood pressure (BP) and hydration status, assessed by whole-body bioimpedance spectroscopy (BIS). We analyzed 463 concomitant measurements of BP, relative overhydration (rel.OH), and plasma sodium (Napl) in 23 children (mean age 13.9 ± 5.1 years).

RESULTS

Pre-dialytic under-hydration (rel.OH < -7%) was present in 5.4% of the sessions, out of which 24% showed hypertension. Normohydration (rel.OH -7 - +7%) was observed in 62.4% of the sessions, 45.3% of them revealed hypertension. Moderate OH (rel.OH +7 - +15%) was present in 21% of the sessions, 47.4% of them showed normal BP. In 11.2% of the sessions, severe overhydration (rel.OH > +15%) was assessed, however, the majority (73%) showed normal BP. Patient-specific Napl setpoint could not be described. Mean dialysate sodium concentration was higher than mean Napl.

CONCLUSIONS

Hypertension is not always related to overhydration. Therefore, BIS should restrict the practice of "probing dry weight" in hypertensive children. Moreover, sodium dialytic balance needs to be considered to improve BP management.

Development of hemodiafiltration therapy--a historical perspective

Hemodiafiltration (HDF) was created in the late 1970s to combine the best of hemodialysis (HD) and hemofiltration, i.e. superior removal of both small and large solutes. Thus, optimal conditions for both diffusion and convection are required. The need for large volumes of sterile fluid has shaped the evolution of HDF, and regulatory issues around systems for on-line fluid preparation have delayed the clinical development of the therapy. Not until such systems became generally available in the mid-1990 s was it possible to increase the efficiency of HDF therapy to match and exceed the upgrade that had taken place for HD. Results from recent studies indicate that the potential for improving the outcome of dialysis lies in increasing the convective clearance of HDF above that of high-flux HD.

Effect of online hemodiafiltration on all-cause mortality and cardiovascular outcomes

In patients with ESRD, the effects of online hemodiafiltration on all-cause mortality and cardiovascular events are unclear. In this prospective study, we randomly assigned 714 chronic hemodialysis patients to online postdilution hemodiafiltration (n=358) or to continue low-flux hemodialysis (n=356). The primary outcome measure was all-cause mortality. The main secondary endpoint was a composite of major cardiovascular events, including death from cardiovascular causes, nonfatal myocardial infarction, nonfatal stroke, therapeutic coronary intervention, therapeutic carotid intervention, vascular intervention, or amputation. After a mean 3.0 years of follow-up (range, 0.4-6.6 years), we did not detect a significant difference between treatment groups with regard to all-cause mortality (121 versus 127 deaths per 1000 person-years in the online hemodiafiltration and low-flux hemodialysis groups, respectively; hazard ratio, 0.95; 95% confidence interval, 0.75-1.20). The incidences of cardiovascular events were 127 and 116 per 1000 person-years, respectively (hazard ratio, 1.07; 95% confidence interval, 0.83-1.39). Receiving high-volume hemodiafiltration during the trial associated with lower all-cause mortality, a finding that persisted after adjusting for potential confounders and dialysis facility. In conclusion, this trial did not detect a beneficial effect of hemodiafiltration on all-cause mortality and cardiovascular events compared with low-flux hemodialysis. On-treatment analysis suggests the possibility of a survival benefit among patients who receive high-volume hemodiafiltration, although this subgroup finding requires confirmation.

Hemodiafiltration: the addition of convective flow to hemodialysis

Hemodiafiltration (HDF) combines both hemofiltration (HF) and hemodialysis in the same procedure. It was initially performed in adults in 1977, and later used in children in the early 1980s. The use of HDF allows a determined convective dialysis dose to be combined with the conventional urea dialysis dose. The dialysis session is better tolerated as a result of the effects of hemofiltration. On-line HDF, i.e., substitution fluid prepared from ultrafiltration of the ultrapure dialysate, can be performed safely due to recent advances in modern technology. However, despite interest and feasibility in children, the majority of pediatric dialysis units across the world still perform hemodialysis using highly permeable membranes, allowing back filtration in the filter and therefore a degree of convective flow, i.e., internal hemodiafiltration. In some countries, government restrictions prohibit the use of on-line hemodiafiltration, (such as the FDA recommendations in North America), and therefore it should not be used in these circumstances.

Optimal hemodialysis prescription: do children need more than a urea dialysis dose?

When prescribing hemodialysis in children, the clinician should first establish an adequate regimen, before seeking to optimize the treatment (Fischbach et al. 2005). A complete dialysis dose should consist of a urea dialysis dose and a determined convective volume. Intensified and more frequent dialysis regimens should not be considered exclusively as rescue therapy. Interestingly, a recent single-center study demonstrated that frequent on-line HDF provides an optimal dialysis prescription, both in terms of blood pressure control (and therefore avoidance of left ventricular hypertrophy), and catch-up growth, that is, no malnutrition or cachexia and less resistance to growth hormone. Nevertheless, this one-center experience would benefit from a prospective randomized study.

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.

Cytokine dysregulation in chronic kidney disease: how can we treat it?

As the kidney is the major site for elimination of many cytokines, the delicate equilibrium of pro-inflammatory cytokines and their inhibitors is clearly dysregulated in chronic kidney disease (CKD) patients. The consequences of the altered immune response in uremia lead to a state of persistent inflammation which is highly prevalent among CKD patients and is linked to complications such as the development of protein-energy wasting and atherosclerotic vascular disease. The present review aims at reviewing this complex orchestration of uremic cytokines beyond the well-studied interleukin-6 and tumor necrosis factor-alpha. Finally, we update our current understanding on anti-inflammatory treatment strategies in CKD patients, including nutritional and lifestyle measurements, pharmacological intervention and specific anticytokine strategies targeting the dialytic procedure.