Achieving high convective volumes in on-line hemodiafiltration

Does online high-volume hemodiafiltration offer greater efficiency and sustainability compared with high-flux hemodialysis? A detailed simulation analysis anchored in real-world data

Recent findings, including the CONVINCE (comparison of high-dose HDF with high-flux HD) study report, suggest the superiority of high-volume hemodiafiltration (HDF) over high-flux hemodialysis (HD) in improving patients' outcomes. Despite positive patient outcomes, concerns have arisen about the potential negative environmental impact of high-volume HDF, as it may lead to increased water and dialysis fluid consumption and higher waste production. In this manuscript, we address the environmental impact of high-volume HDF, focusing on three key factors: water treatment consumption, dialysis fluid consumption, and solute efficiency markers of HD and HDF. By optimizing HDF prescription through adjustments in operational capabilities, while keeping a high blood flow (i.e., >350 ml/min) such as reducing the QD/QB ratio to 1.2 rather than 1.4 or 1.5 and incorporating automated ultrafiltration and substitution control, we demonstrate that HDF delivers a higher dialysis dose for small- and middle-molecule uremic compounds with the same dialysis fluid consumption, and at equal dialysis doses dialysis fluid consumption is reduced. This finding is supported by real-world data from 26 031 patients who underwent high-volume postdilution HDF at a reduced dialysis flow (430 mL/min) and achieved an effective OCMKt/V of 1.70 (where "OCM" stands for online clearance measurement, "K" represents effective dialysis clearance and "V" denotes total body water measured by multifrequency bioimpedance). In addition, simulation modeling calculations, using blood extraction coefficient, dialysate saturation coefficient and solute clearances with urea (small molecular weight) and β2-microglobulin (middle molecular weight), consistently show the superiority of postdilution HDF to HD. This holds true even with a significant reduction in dialysis flow down to 430 mL/min, reflecting QD/QB ratio of 1.2. Postdilution HDF generates high ultrafiltrate flow (up to 35% of blood flow), delivering saturated ultrafiltrate to the lower solute concentration containing effluent dialysate, thus enhancing solute clearance which opens the way to reduce the dialysis flow. In conclusion, our analysis, combining simulation and real-world data, suggests that postdilution HDF could be a more environmentally friendly treatment option compared with conventional HD. Additionally, automated user-friendly functions that minimize dialysis fluid use can further strengthen this environmental benefit while enhancing efficiency.

ABCs of hemodiafiltration prescription: The Pisa style

In end-stage kidney disease patients, hemodiafiltration, a mixed diffusive-convective technique, has shown beneficial effects in terms of improvement of anemia, inflammation, mineral bone disorders, malnutrition and cardiovascular stability. Greater convective volume exchange was also associated with improved overall and cardiovascular survival. However, absolute target threshold volume would be difficult to define and achieve in daily clinical practice, mainly because of differences in patient size. Convective volumes standardized for body surface area would appear to be the simplest approach in clinical practice. Several factors can affect achievement of optimal convective volume, with vascular access being the main limiting factor. Based on our own clinical experience, hemodiafiltration is a more effective and preferable dialysis technique but only when a target convective volume greater than 20 L can be achieved. Conversely, standard high flux hemodialysis or expanded hemodialysis may be helpful and valuable alternative dialysis techniques.

Hemodiafiltration: Technical and Medical Insights

Despite the significant medical and technical improvements in the field of dialytic renal replacement modalities, morbidity and mortality are excessively high among patients with end-stage kidney disease, and most interventional studies yielded disappointing results. Hemodiafiltration, a dialysis method that was implemented in clinics many years ago and that combines the two main principles of hemodialysis and hemofiltration-diffusion and convection-has had a positive impact on mortality rates, especially when delivered in a high-volume mode as a surrogate for a high convective dose. The achievement of high substitution volumes during dialysis treatments does not only depend on patient characteristics but also on the dialyzer (membrane) and the adequately equipped hemodiafiltration machine. The present review article summarizes the technical aspects of online hemodiafiltration and discusses present and ongoing clinical studies with regards to hard clinical and patient-reported outcomes.

Why should we focus on high-volume hemodiafiltration?

Though noticeable technological advances related to hemodialysis (HD) have been made, unfortunately, the survival rate of dialysis patients has yet to improve significantly. However, recent research findings reveal that online hemodiafiltration (HDF) significantly improves patient survival in comparison to conventional HD. Accordingly, the number of patients receiving online HDF is increasing. Although the mechanism driving the benefit has not yet been fully elucidated, survival advantages are mainly related to the lowering of cardiovascular mortality. High cardiovascular mortality among HD patients is seemingly attributable to the cardiovascular changes that occur in response to renal dysfunction and the HD-induced myocardial stress and injury, and online HDF appears to improve such secondary cardiovascular changes. Interestingly, patient survival improves only if the convection volume is supplied sufficiently over a certain level during online HDF treatment. In other words, survival improvement from online HDF is related to convection volume. Therefore, there is a growing interest in high-volume HDF in terms of improving the survival rate. The survival improvement will require a minimum convection volume of 23 L or more per 4-hour session for postdilution HDF. To obtain an optimal high convection volume in online HDF, several factors, such as the treatment time, blood flow rate, filtration fraction, and dialyzer, need to be considered. High-volume HDF can be performed easily and safely in routine clinical practice. Therefore, when the required equipment is available, performing high-volume HDF will help to improve the survival rate of dialysis patients.

Basic prerequisites for on-line, high-volume hemodiafiltration

High-volume hemodiafiltration involves filtration of >23 L/treatment and its replacement by sterile non-pyrogenic substitution fluid, while maintaining the patient's fluid balance. That volume of substitution fluid precludes the use of prepackaged sterile fluid. Instead, substitution fluid must be prepared on-line using machines that incorporate a series of bacteria- and endotoxin-retentive filters. The sterilizing ultrafilters are validated to deliver sterile, non-pyrogenic fluid to the patient when operated according to the machine manufacturer's instructions and in compliance with international standards and regulatory oversight. A successful hemodiafiltration program also places important responsibilities on the user. Specifically, the user is responsible for ensuring that the dialysis water or dialysis fluid delivered to the sterilizing filters of the hemodiafiltration machine meets the machine manufacturer's specifications and is consistent with the quality used in the sterilization validation process. The user is also responsible for ensuring that the treatment prescription allows a filtration volume >23 L/treatment to be achieved by careful selection of a dialyzer, blood flow rate and treatment time. Questions related to assurance that the substitution fluid will routinely be sterile and non-pyrogenic have limited the uptake of on-line hemodiafiltration as a therapeutic option in some countries, such as the United States.

Switching from high-flux dialysis to hemodiafiltration: Cost-consequences for patients, providers, and payers

Hemodiafiltration (HDF) achieves a more efficient reduction of the uremic toxic load compared to standard high-flux hemodialysis (HF-HD) by virtue of the combined diffusive and convective clearances of a broad spectrum of uremic retention solutes. Clinical trials and registry data suggest that HDF improves patient outcomes. Despite the acknowledged need to improve survival rates of dialysis patients and the survival benefit HDF offers, there is little to no utilization in some countries (such as the US) in prescribing HDF to their patients. In this analysis, we present the healthcare value-based case for HDF (relative to HF-HD) from the patient, provider, and payor perspectives. The improved survival and reduced morbidity observed in studies conducted outside the US, as well as the reduced hospitalization, are attractive for each stakeholder. We also consider the potential barriers to greater utilization of HDF therapies, including unfounded concerns regarding additional costs of HDF, e.g., for the preparation and microbial testing of quality of substitution fluids. Ultrapure fluids are easily attainable and prepared from dialysis fluids using established "online" (OL) technologies. OL-HDF has matured to a level whereby little additional effort is required to safely implement it as all modern machine systems are today equipped with the OL-HDF functionality. Countries already convinced of the advantages of HF-HD are thus well positioned to make the transition to OL-HDF to achieve further clinical and associated economic benefits. Healthcare systems struggling to cope with the increasing demand for HD therapies would therefore, like patients, be beneficiaries in the long term with increased usage of OL-HDF for end stage kidney disease patients.

Global real-world data on hemodiafiltration: An opportunity to complement clinical trial evidence

Hemodiafiltration (HDF) is a renal replacement therapy that utilizes both diffusive clearance and convective transport to achieve greater clearance of middle-molecular-weight solutes. Among other factors, important prerequisites for the implementation of HDF include access to high-flux dialyzers, achievement of high blood flow rates, and availability of high volumes of sterile substitution/replacement fluids. Online hemodiafiltration (OL-HDF) is an established kidney replacement therapy, frequently used in many countries. Although in the United States, some prerequisites (e.g., access to high-flux dialyzers and achievement of high blood flow rates) for OL-HDF treatment are readily available; however, a machine capable of generating the online solution for OL-HDF is currently not available. As the clinical experience with HDF accumulates globally, it is worth examining the evidence for this kidney replacement therapy as used in routine clinical care. Such real-world evidence is increasingly recognized as valuable by clinicians and may inform regulatory decisions. In this review, we will focus on emerging global real-world data derived from routine clinical practices and examine how these data may complement those derived from clinical trials.

Informed decision-making in delivery of dialysis: combining clinical outcomes with sustainability

As the prevalence of chronic kidney disease is expected to rise worldwide over the next decades, provision of renal replacement therapy (RRT), will further challenge budgets of all healthcare systems. Most patients today requiring RRT are treated with haemodialysis (HD) therapy and are elderly. This article demonstrates the interdependence of clinical and sustainability criteria that need to be considered to prepare for the future challenges of delivering dialysis to all patients in need. Newer, more sustainable models of high-value care need to be devised, whereby delivery of dialysis is based on value-based healthcare (VBHC) principles, i.e. improving patient outcomes while restricting costs. Essentially, this entails maximizing patient outcomes per amount of money spent or available. To bring such a meaningful change, revised strategies having the involvement of multiple stakeholders (i.e. patients, providers, payers and policymakers) need to be adopted. Although each stakeholder has a vested interest in the value agenda often with conflicting expectations and motivations (or motives) between each other, progress is only achieved if the multiple blocs of the delivery system are advanced as mutually reinforcing entities. Clinical considerations of delivery of dialysis need to be based on the entire patient disease pathway and evidence-based medicine, while the non-clinical sustainability criteria entail, in addition to economics, the societal and ecological implications of HD therapy. We discuss how selection of appropriate modes and features of delivery of HD (e.g. treatment modalities and schedules, selection of consumables, product life cycle assessment) could positively impact decision-making towards value-based renal care. Although the delivery of HD therapy is multifactorial and complex, applying cost-effectiveness analyses for the different HD modalities (conventional in-centre and home HD) can support in guiding payability (balance between clinical value and costs) for health systems. For a resource intensive therapy like HD, concerted and fully integrated care strategies need to be urgently implemented to cope with the global demand and burden of HD therapy.

Clinical relevance of abstruse transport phenomena in haemodialysis

Haemodialysis (HD) utilizes the bidirectional properties of semipermeable membranes to remove uraemic toxins from blood while simultaneously replenishing electrolytes and buffers to correct metabolic acidosis. However, the nonspecific size-dependent transport across membranes also means that certain useful plasma constituents may be removed from the patient (together with uraemic toxins), or toxic compounds, e.g. endotoxin fragments, may accompany electrolytes and buffers of the dialysis fluids into blood and elicit severe biological reactions. We describe the mechanisms and implications of these undesirable transport processes that are inherent to all HD therapies and propose approaches to mitigate the effects of such transport. We focus particularly on two undesirable events that are considered to adversely affect HD therapy and possibly impact patient outcomes. Firstly, we describe how loss of albumin (and other essential substances) can occur while striving to eliminate larger uraemic toxins during HD and why hypoalbuminemia is a clinical condition to contend with. Secondly, we describe the origins and mode of transport of biologically active substances (from dialysis fluids with bacterial contamination) into the blood compartment and biological reactions they elicit. Endotoxin fragments activate various proinflammatory pathways to increase the underlying inflammation associated with chronic kidney disease. Both phenomena involve the physical as well as chemical properties of membranes that must be selected judiciously to balance the benefits with potential risks patients may encounter, in both the short and long term.

Public health benefits of water purification using recycled hemodialyzers in developing countries

In rural regions with limited resources, the provision of clean water remains challenging. The resulting high incidence of diarrhea can lead to acute kidney injury and death, particularly in the young and the old. Membrane filtration using recycled hemodialyzers allows water purification. This study quantifies the public health effects. Between 02/2018 and 12/2018, 4 villages in rural Ghana were provided with a high-volume membrane filtration device (NuFiltration). Household surveys were collected monthly with approval from Ghana Health Services. Incidence rates of diarrhea for 5-month periods before and after implementation of the device were collected and compared to corresponding rates in 4 neighboring villages not yet equipped. Data of 1,130 villagers over 10 months from the studied communities were studied. Incidence rates showed a decline following the implementation of the device from 0.18 to 0.05 cases per person-month (ppm) compared to the control villages (0.11 to 0.08 ppm). The rate ratio of 0.27 for the study villages is revised to 0.38 when considering the non-significant rate reduction in the control villages. Provision of a repurposed hemodialyzer membrane filtration device markedly improves health outcomes as measured by diarrhea incidence within rural communities.

The renal replacement therapy landscape in 2030: reducing the global cardiovascular burden in dialysis patients

Despite the significant progress made in understanding chronic kidney disease and uraemic pathophysiology, use of advanced technology and implementation of new strategies in renal replacement therapy, the clinical outcomes of chronic kidney disease 5 dialysis patients remain suboptimal. Considering residual suboptimal medical needs of short intermittent dialysis, it is our medical duty to revisit standards of dialysis practice and propose new therapeutic options for improving the overall effectiveness of dialysis sessions and reduce the burden of stress induced by the therapy. Several themes arise to address the modifiable components of the therapy that are aimed at mitigating some of the cardiovascular risks in patients with end-stage kidney disease. Among them, five are of utmost importance and include: (i) enhancement of treatment efficiency and continuous monitoring of dialysis performances; (ii) prevention of dialysis-induced stress; (iii) precise handling of sodium and fluid balance; (iv) moving towards heparin-free dialysis; and (v) customizing electrolyte prescriptions. In summary, haemodialysis treatment in 2030 will be substantially more personalized to the patient, with a clear focus on cardioprotection, volume management, arrhythmia surveillance, avoidance of anticoagulation and the development of more dynamic systems to align the fluid and electrolyte needs of the patient on the day of the treatment to their particular circumstances.

Does subjective assessment of dialyzer appearance reflect dialyzer performance in online hemodiafiltration?

Introduction: In post‐dilution online hemodiafiltration, a very thin balance subsists in preventing coagulation of the extracorporeal circuit (ECC) during treatment and bleeding in the patient, concerning dialyzer status and anticoagulation dose.

The aim of this study was to assess whether there are clinical outcome differences between the visual aspect of the dialyzer's status in terms of clotted fibers at end of dialysis treatments, single‐pool urea kinetic modeling (spKt/V) and substitution volume (SubsVol).

Methods: It is a multicenter, descriptive‐correlational study, involving 2829 patients during April 2016. Previous training was given to the Nursing staff to evaluate and classify both the dialyzer's and the venous chamber's appearance of the ECC venous line. Registration was performed at bedside immediately after the patient disconnection.

Findings and discussion: Mean age was 68.96 years (SD = 13.75), 60.8% were men. The average hematocrit was 33.91% (SD = 3.45%). The average dry weight was 68.53 kg (SD = 13.27 kg). Mean unfractioned heparin (UFH) dose was 58.13 IU/kg. Only 32.4% of the patients had a clean dialyzer at the end of treatment. 19.4% of patients finished the treatment with more than 10% of clotted fibers. Patients with no residual blood (clean, 32.4%) presented a higher UFH dose (66.32 IU/kg) compared to overall average dose. UFH dose had a significant effect on dialyzer status. There were significant differences in average of spKt/V and SubsVol between the category clean and the other categories of dialyzer's status.

Evaluating the dialyzer status represents an excellent opportunity to help the physicians to establish an ideal heparin dose. Only the category clean is significant to achieve the target. The nursing staff, by classifying the ECC appearance at patient's bedside and recording it in a centralized database, can be a major contributor to achieve an individualized and optimal UFH dose and subsequently better patient outcomes.

Global prevalent use, trends and practices in haemodiafiltration

Online haemodiafiltration (HDF) represents today the most advanced and innovative form of renal replacement therapy (RRT). Recent controlled trials tend to prove its superiority over conventional haemodialysis on hard clinical end points provided that the right convective dose was delivered. In this article we report on present prevalent use and epidemiologic trends of HDF worldwide as well as on practice patterns in HDF prescription. In addition we analyze factors that may affect HDF clinical acceptance and more widely its implementation. National and international renal registries provide valuable demographic and epidemiologic information on end stage kidney disease patients on RRT. However, the updating and maintenance of such information system is particularly challenging at a country level and even more so on an international basis. Lag time, incompleteness and/or imprecision of data collection may further hamper precision and validity of data reporting. Fresenius Medical Care (FMC), as a large dialysis care provider operating worldwide, maintains an annually updated database addressing international end stage kidney disease data. Over the last decade, FMC has produced series of precise and reliable reports analyzing RRT trends and practices worldwide. The present overview and analysis is based on our consolidated data from market survey as well as national database registries and databases of recent studies. Online HDF acceptance is growing fast in the two leading regions having approved the method, i.e. Europe and Asia Pacific, with a patient average growth rate of 12 to 24%, being far above the total patient HD growth rate of 6.6%. Today online HDF represents a new paradigm shift in RRT with promising clinical results. Further initiatives (e.g., Kidney Health Initiative, NICE) might provide further push for promoting HDF as a new standard of care in end stage kidney disease patients on a global scale.

Hemodiafiltration to Address Unmet Medical Needs ESKD Patients

Hemodiafiltration combines diffusive and convective solute removal in a single therapy by ultrafiltering 20% or more of the blood volume processed using a high-flux hemodialyzer and maintaining fluid balance by infusing sterile nonpyrogenic replacement fluid directly into the patient's blood. In online hemodiafiltration, the large volumes of replacement fluid required are obtained by online filtration of standard dialysate through a series of bacteria- and endotoxin-retaining filters. Currently available systems for online hemodiafiltration are on the basis of conventional dialysis machines with added features to safely prepare and infuse replacement fluid and closely control fluid balance. Hemodiafiltration provides greater removal of higher molecular weight uremic retention solutes than conventional high-flux hemodialysis, and recently completed randomized, controlled clinical trials suggest better patient survival with online hemodiafiltration compared with standard high-flux hemodialysis when a high convection volume is delivered. Hemodiafiltration is also associated with improvements in other clinical outcomes, such as a reduction in intradialytic hypotension, and it is now used routinely to treat >100,000 patients, mainly in Europe and Japan.

Asymmetric cellulose triacetate is a safe and effective alternative for online haemodiafiltration

BACKGROUND

In post-dilution haemodiafiltration only synthetic membranes have been used to date. Asymmetric cellulose triacetate (ATA™) is now available, whose characteristics are suitable for this technique.

OBJECTIVES

To describe the in vivo performance and behaviour of this membrane, to identify its depurative effectiveness, use in clinical practice and its biocompatibility, both acute and after one month of treatment.

METHODS

Observational prospective study of 23 patients who were dialysed for 4 weeks using an ATA™ membrane and who maintained their prior regimen.

RESULTS

A total of 287 sessions were performed and 264 complete sessions were collected. With an effective time of 243.7 (17.6) min and a mean blood flow of 371.7 (23) ml/min, an average Kt of 56.3 (5.3) l was observed, as well as a convection volume of 27.1 (4.2) l, a filtration fraction of 29.9 (3.7) %, a urea reduction ratio (RR) of 81 (5.2) %, a creatinine RR of 74.7 (4.6) %, a β₂-microglobulin RR of 76.5 (4.8) % and a retinol binding protein RR of 18.6 (7.6) %. There were no technical problems or alarms. Changing the heparin dosage was not necessary. No increases in C3a or C5a concentrations or leukopenia were observed in the first 30min of the session. Neither the monocyte subpopulations nor IL-β1 or IL-6 were significantly altered after one month of treatment.

CONCLUSIONS

The new ATA™ membrane achieves adequate Kt and convection volume, without technical problems and with good biocompatibility and inflammatory profiles. It is therefore a valid option for post-dilution haemodiafiltration, particularly in patients allergic to synthetic membranes.

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.

Optimal convection volume for improving patient outcomes in an international incident dialysis cohort treated with online hemodiafiltration

Online hemodiafiltration (OL-HDF), the most efficient renal replacement therapy, enables enhanced removal of small and large uremic toxins by combining diffusive and convective solute transport. Randomized controlled trials on prevalent chronic kidney disease (CKD) patients showed improved patient survival with high-volume OL-HDF, underlining the effect of convection volume (CV). This retrospective international study was conducted in a large cohort of incident CKD patients to determine the CV threshold and range associated with survival advantage. Data were extracted from a cohort of adult CKD patients treated by post-dilution OL-HDF over a 101-month period. In total, 2293 patients with a minimum of 2 years of follow-up were analyzed using advanced statistical tools, including cubic spline analyses for determination of the CV range over which a survival increase was observed. The relative survival rate of OL-HDF patients, adjusted for age, gender, comorbidities, vascular access, albumin, C-reactive protein, and dialysis dose, was found to increase at about 55 l/week of CV and to stay increased up to about 75 l/week. Similar analysis of pre-dialysis β2-microglobin (marker of middle-molecule uremic toxins) concentrations found a nearly linear decrease in marker concentration as CV increased from 40 to 75 l/week. Analysis of log C-reactive protein levels showed a decrease over the same CV range. Thus, a convection dose target based on convection volume should be considered and needs to be confirmed by prospective trials as a new determinant of dialysis adequacy.

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.

Survival of incident patients on high-volume online hemodiafiltration compared to low-volume online hemodiafiltration and high-flux hemodialysis

BACKGROUND

Hemodiafiltration is becoming a preferred treatment modality for dialysis patients in many countries. The volume of substitution fluid delivered has been indicated as an independent mortality risk factor. The aim of this study is to compare patient survival on three different treatment modalities: high-flux hemodialysis, low-volume online HDF (oHDF) and high-volume oHDF.

METHODS

Incident hemodialysis and oHDF patients treated in 13 NephroCare centers in Bosnia and Herzegovina, Serbia and Slovenia between January 1, 2007, and December 31, 2011, were included in this epidemiological cohort study. High-volume oHDF was defined as substitution volume higher than the median substitution volume infused, otherwise low-volume. Main predictor was treatment modality at baseline and in time-dependent model. Other predictors were age, gender, diabetes mellitus, cerebrovascular accident, arrhythmia, hemoglobin and C-reactive protein.

RESULTS

Four hundred and forty-two patients were included in the study. Median substitution fluid volume was 20.4 L. Mean difference between the oHDF groups in substitution fluid volume was 8.3 ± 5.2 L [95 % confidence intervals (95 % CI) 7.1-9.5, p < 0.0001]. The unadjusted hazard ratios (HR) with 95 % CI compared to high-flux HD were 0.87 (0.5-1.5) for low-volume oHDF and 0.29 (0.13-0.63) for high-volume oHDF. After the adjustment for covariates, the HR for patients on low-volume oHDF remained statistically insignificant compared to high-flux HD (0.84; 95 % CI 0.46-1.53), while patients on high-volume oHDF showed a marked and significantly lower HR (0.29; 95 % CI 0.13-0.68) than patients on high-flux HD in baseline model. While this effect failed to reach significance in the time-dependent model (HR 0.477; 95 % CI 0.196-1.161), possibly due to an inadequate sample size here, the consistency of results in both models supports the robustness of the findings. After switching from high-flux hemodialysis to oHDF, mean hemoglobin and albumin levels did not change significantly. Mean erythropoietin resistance index (ERI) and erythropoiesis stimulating agents (ESA) consumption decreased significantly (p = 0.02, p = 0.03, respectively).

CONCLUSIONS

The median substitution volume used in these three countries for post-dilutional oHDF is 20.4 L. oHDF is associated with significant reductions in ERI and ESA consumption. Only high-volume oHDF is associated with improved survival compared to high-flux hemodialysis.