Efficacy of slow daily home hemodialysis with internal convection on removal of uremic toxins using the Physidia S3 monitor

Home hemodialysis, despite its recognized clinical benefits such as improved cardiac health and enhanced quality of life, remains underutilized worldwide. This study aims to evaluate the efficacy of home hemodialysis within slow daily dialysis programs, employing the Physidia S3 monitor. A prospective trial was conducted with 16 stable patients suffering from end-stage kidney disease and undergoing home hemodialysis. The study assessed the efficiency of slow daily short treatment dialysis using diverse criteria, including percent reduction, effective clearances, and solute mass removal, across a broad spectrum of uremic compounds, including sodium. Controlled sessions were implemented to replicate daily home treatment conditions. Selecting urea and ß2M as key biomarkers due to their associations with patient outcomes, our study achieved a standardized weekly Kt/V of 2.26 [1.99-2.70] and estimated kidney urea clearance of 11.4 [10.9-12.4] mL/min. ß2M mass removal per session was 146 mg, extrapolating to 707 (×5) and 845 (×6) mg weekly. Additionally, the time-averaged concentration of ß2M was maintained at 19.4 mg/L. The study also identified a net sodium mass removal of 126 mmol [98-182] or 7.4 g [5.8-10.7] NaCl per session. In conclusion, our findings suggest that slow daily, short treatment time, high flux hemodialysis, augmented by enhanced internal convective clearance, represents a highly efficient renal replacement modality on a weekly basis across large molecular weight uremic compounds. Moreover, the solute dialysate saturation coefficient emerges as a promising marker in slow-flow settings.

Assessment of Safety and Efficacy of Expanded Hemodialysis with Medium Cut-Off Dialyzer Compared to Haemodiafiltration

Background: Removal of large uraemic toxins is still a challenge. Haemodiafiltration (HDF) has produced some results, although large convective volume, optimal vascular access to increase the blood flow rate and strict water quality management are required. Medium cut-off, high-retention-onset membranes have been recently developed, introducing the concept therapy called expanded haemodialysis (HDx). Furthermore, vitamin E-coated membrane has potential beneficial effects on inflammation and oxidative stress. Methods: A prospective longitudinal multicentre study was conducted for 3 months among 24 chronic haemodialysis patients. Patients were randomly assigned into either HDF with high-flux membrane or HDx with Theranova or ViE-X membrane. The primary goal was to assess albumin loss among the three types of dialyzers. Secondary goals included assessment of depurative efficacy for uraemic toxins and clinical outcomes. Results: Mean albumin loss was significantly higher in patients undergoing HDx with Theranova membrane, without any difference in serum albumin concentration among the three groups. Instantaneous clearance of small and middle molecules was significantly higher in patients undergoing HDF, but we did not find differences in removal ratio and Kt/V. Reduction in the erythropoietin resistance index was observed in patients treated with ViE-X membrane due to their lower dialysis vintage. Conclusions: The higher albumin loss during HDx has no effects on pre-dialysis serum albumin. HDx with Theranova in the presence of lower session length, lower Qb, lower convective dose, and lower instantaneous clearance reached the same dialysis efficacy compared to HDF.

Comparison of citrate dialysate in pre- and post-dilution online hemodiafiltration: effect on clot formation and adequacy of dialysis in hemodialysis patients

BACKGROUND

Citrate dialysate (CD) has been successfully used in conventional hemodialysis and continuous renal replacement therapy; however, no study has compared pre- and post-dilution online hemodiafiltration (oL-HDF). Therefore, we aimed to investigate the efficacy of citrate anticoagulation for oL-HDF and the metabolic changes and quality of life of patients on hemodialysis treated using both modes.

METHOD

Eight dialysis patients were treated with CD containing 0.8 mmol of citric acid for 4 weeks in each phase. Visual clotting scores were investigated as the primary endpoints. Adequacy of dialysis, laboratory parameters, and quality of life were measured as secondary objectives.

RESULTS

The mean clotting scores in the pre-dilution mode were significantly lower than those in the post-dilution mode and in all phases except the heparin-free phase (p < 0.001 in the baseline phase, p = 0.001 in phase 1, and p = 0.023 in phase 2). The values of Kt/V in both modalities were comparable except during the baseline phase, in which the values of pre-dilution were significantly greater than post-dilution (2.36 ± 0.52/week vs. 1.87 ± 0.33/week;95% CI -0.81 to -0.19, p = 0.002). The patient's quality of life regarding their physical activity level was significantly higher in the post-dilution mode than in the pre-dilution mode at baseline and in phase 1 (p = 0.014 and 0.004 at baseline and in phase 1, respectively). Metabolic changes did not differ between the two modes.

CONCLUSION

Citrate dialysate decreased or prevented anticoagulation in both pre- and post-dilution modes of oL-HDF without significant side effects and had comparable adequacy of dialysis.

Hemodiafiltration May Be Associated with Senescence-Related Phenotypic Alterations of Lymphocytes, Which May Predict Mortality in Patients Undergoing Dialysis

Senescence-resembling alterations on the lymphocytes of patients undergoing dialysis have been widely described. However, the pathophysiology behind these phenomena has not been clarified. In this study, we examined the impact of dialysis prescription on T and B lymphocytes, in patients undergoing dialysis.: T and B cell subsets were determined with flow cytometry in 36 patients undergoing hemodialysis and 26 patients undergoing hemodiafiltration, according to the expression of CD45RA, CCR7, CD31, CD28, CD57, and PD1 for T cells, and IgD and CD27 for B cells. The immune phenotype was associated with dialysis modality, hemofiltration volume, and mortality. Compared with hemodialysis, patients undergoing hemodiafiltration had a significantly decreased percentage of CD4+CD28-CD57- T cells [3.8 (2.4-5.3) vs. 2.1 (1.3-3.3)%, respectively, p = 0.002] and exhausted CD4+ T cells [14.1 (8.9-19.4) vs. 8.5 (6.8-11.7)%, respectively, p = 0.005]. Additionally, the hemofiltration volume was negatively correlated with CD8+ EMRA T cells (r = -0.46, p = 0.03). Finally, the increased exhausted CD4+ T cell percentage was associated with increased all-cause mortality in patients undergoing dialysis, independent of age. Hemodiafiltration, especially with high hemofiltration volume, may have beneficial effects on senescence-related immune phenotypes. Immune phenotypes may also be a predicting factor for mortality in patients undergoing dialysis.

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.

Calcium mass balance in adults during single hemodialysis and hemodiafiltration treatments using lower calcium dialysate concentrations

BACKGROUND

Debate continues as to the optimum hemodialysis (HD) dialysate calcium concentration. Although current guidelines advocate 1.25-1.5 mmol/L, some investigators have suggested these may cause calcium gains. As such we investigated whether using dialysate calcium of 1.25 mmol/L risked calcium gains, and whether there were differences between hemodiafiltration and high flux HD.

METHODS

We continuously collect an aliquot of effluent dialysate during dialysis sessions, and calculated dialysis calcium mass balance by the difference between the amount of calcium delivered as fresh dialysate and that lost in effluent dialysate.

RESULTS

We studied 106 stable outpatients, 64% male, mean age 64.4 ± 16.2 years, median dialysis vintage 32 (22-60) months. Most sessions (69%) used a 1.0 mmol/L calcium dialysate, with a median sessional loss of 13.7 (11.5-17.1) mmol, whereas using 1.25 mmol/L the median loss was 7.4 (4.9-10.1) mmol, but with 6.9% had a positive balance (p = 0.031 vs dialysate calcium 1.0 mmol/L). Most patients (85.8%) were treated by hemodiafiltration, but there was no difference in sessional losses (11.7 (8.4-15.8) vs 13.5 (8.1-16.8)) with high flux HD. Dialysis sessional calcium balance was associated with the use of lower dialysate calcium concentration (β -19.5, 95% confidence limits (95%CL) -27.7 to -11.3, p < 0.001), and sessional duration (β 0.07 (95% CL) 0.03-012, p = 0.002).

CONCLUSION

Ideally, the choice of dialysate calcium should be individualized, but clinicians should be aware, that even when using a dialysate calcium of 1.25 mmol/L, some patients are at risk of a calcium gain during hemodiafiltration and high-flux hemodialysis.

Kinetics of β -2-Microglobulin with Hemodiafiltration and High-Flux Hemodialysis

Key Points

Addition of hemodiafiltration has a relatively small impact on reducing either predialysis or time-averaged serum β -2-microglobulin levels. Residual kidney function has a major impact on the predialysis and time-averaged serum β -2-microglobulin levels.

Background

A kinetic model for β -2-microglobulin removal and generation was used to explore the impact of adding hemodiafiltration on predialysis and time-averaged serum values.

Methods

The model was tested on data from the HEMO study and on a sample of patients undergoing high-flux hemodialysis. The impact of hemodiafiltration on β -2-microglobulin levels was evaluated by modeling four randomized studies of hemodiafiltration versus hemodialysis. The impact of residual kidney function on β -2-microglobulin was tested by comparing results of previously reported measured data with model predictions.

Results

In the low-flux and high-flux arms of the HEMO study, measured median β -2-microglobulin reduction ratios could be matched by dialyzer clearances of 5.9 and 29 ml/min, respectively. Median predialysis serum β -2-microglobulin levels were matched if generation rates of β -2-microglobulin were set to approximately 235 mg/d. In another group of patients treated with dialyzers with increased β -2-microglobulin clearances, measured cross-dialyzer clearances (57±28 ml/min) were used as inputs. In these studies, the kinetic model estimates of intradialysis and early postdialysis serum β -2-microglobulin levels were similar to median measured values. The model was able to estimate the changes in predialysis serum β -2-microglobulin in each of four published randomized comparisons of hemodiafiltration with hemodialysis, although the model predicted a greater decrease in predialysis serum β -2-microglobulin with hemodiafiltration than was reported in two of the studies. The predicted impact of residual kidney clearance on predialysis serum β -2-microglobulin concentrations was similar to that reported in one published observational study. Modeling predicted that postdilution hemodiafiltration using 25 L/4 hours replacement fluid would lower serum time-averaged concentration of β -2-microglobulin by about 18.2%, similar to the effect of 1.50 ml/min residual kidney GFR.

Conclusions

A two-pool kinetic model of β -2-microglobulin yielded values of reduction ratio and predialysis serum concentration that were consistent with measured values with various hemodiafiltration and hemodialysis treatment regimens.

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.

Hemodiafiltration versus Hemodialysis in End-Stage Kidney Disease: A Systematic Review and Meta-Analysis

Rationale & Objective

The use of hemodiafiltration (HDF) as a kidney replacement therapy (KRT) in patients with end-stage kidney disease (ESKD) has sparked a debate regarding its advantages over conventional hemodialysis (HD). The present study aims to shed light on this controversy by comparing mortality rates and cause-specific deaths between ESKD patients receiving HDF and those undergoing HD.

Study Design

Systematic review and meta-analysis of randomized controlled trials (RCTs). The search was conducted using PubMed, EMBASE, and Cochrane Central on July 1, 2023.

Setting & Participants

Adult patients with ESKD on regular KRT.

Exposure

Studies with participants undergoing HDF.

Outcomes

Primary outcomes were all-cause mortality, cardiovascular (CV) mortality, deaths related to infections, and kidney transplant. We also evaluated the endpoints for deaths related to malignancy, myocardial infarction, stroke, arrhythmias, and sudden death.

Analytical Approach

We included RCTs evaluating HDF versus HD. Crossover trials and studies with overlapping populations were excluded. Two authors independently extracted the data following predefined search criteria and quality assessment. The risk of bias was assessed with Cochrane's RoB2 tool.

Results

We included 5 RCTs with 4,143 patients, of which 2,078 (50.1%) underwent HDF, whereas 2,065 (49.8%) were receiving HD. Overall, HDF was associated with a lower risk of all-cause mortality (risk ratio [RR], 0.81; 95% confidence interval [CI], 0.73-0.91; P < 0.001; I2 = 7%) and a lower risk of CV-related deaths (RR, 0.75; 95% CI, 0.61-0.92; P = 0.007; I2 = 0%). The incidence of infection-related deaths was also significantly different between therapies (RR, 0.69; 95% CI, 0.50-0.95; P = 0.02; I2 = 26%).

Limitations

In individual studies, the HDF groups achieved varying levels of convection volume.

Conclusions

Compared with those undergoing HD, patients receiving HDF experienced a reduction in all-cause mortality, CV mortality, and infection-related mortality. These results provide compelling evidence supporting the use of HDF as a beneficial intervention in ESKD patients undergoing KRT.

Registration

Registered at PROSPERO: CRD42023438362.

High volume online hemodiafiltration: a global perspective and the Brazilian experience

Online hemodiafiltration (HDF) is a rapidly growing dialysis modality worldwide. In Brazil, the number of patients with private health insurance undergoing HDF has exceeded the number of patients on peritoneal dialysis. The achievement of a high convection volume was associated with better clinical imprand patient - reported outcomes confirming the benefits of HDF. The HDFit trial provided relevant practical information on the implementation of online HDF in dialysis centers in Brazil. This article aims to disseminate technical information to improve the quality and safety of this new dialysis modality.

Controversy on the CONVINCE study findings: the PRO take

The CONVINCE study, recently published in the New England Journal of Medicine, reveals a groundbreaking 23% reduction in the relative risk of all-cause mortality among end-stage kidney patients undergoing high convective volume hemodiafiltration. This significant finding challenges the conventional use of high-flux hemodialysis and offers hope for improving outcomes in chronic kidney disease patients. While some controversies surround the study's findings, including concerns about generalizability and the causes of death, it is essential to acknowledge the study's design and its main outcomes. The CONVINCE study, part of the HORIZON 2020 project, enrolled 1360 patients and demonstrated the superiority of hemodiafiltration in reducing all-cause mortality overall, as well as in specific patient subgroups (elderly, short vintage, non-diabetic, and those without cardiac issues). Interestingly, it was shown that hemodiafiltration had a protective effect against infection, including COVID-19. Future research will address sustainability, dose scaling effects, identification of subgroups especially likely to benefit and cost-effectiveness. However, for now, the findings strongly support a broader adoption of hemodiafiltration in renal replacement therapy, marking a significant advancement in the field.

Dosing lutetium Lu 177-dotatate for a hemodialysis patient

Lu177-dotatate (Lutathera™) is a radioactive drug approved for the treatment of adults with gastro-entero-pancreatic neuroendocrine tumors and is predominantly renally excreted. Currently all patients receive 7400 MBq (200 mCi), and there are no guidelines for treating hemodialysis patients. We measured radioactivity prior to and post administration of two cycles of Lu177-dotatate in a hemodialysis patient, and radiation exposure to staff. We reduced the standard 7400 MBq by 33% for the first cycle and patient radioactivity fell by 40% following postdilution hemodiafiltration started 6 h post dosing, and by 45% for the second cycle and radioactivity fell by 47% with postdilution hemodiafiltration started 5 h post administration. By reducing the initial administered radioactivity, coupled with early dialysis, and choosing postdilution hemodiafiltration we were able to achieve radioactivity retention curves similar to those from patients with normal renal function receiving the standard administration of 7400 MBq.

Effect of Membrane Permeance and System Parameters on the Removal of Protein-Bound Uremic Toxins in Hemodialysis

Inadequate clearance of protein-bound uremic toxins (PBUTs) during dialysis is associated with morbidities in chronic kidney disease patients. The development of high-permeance membranes made from materials such as graphene raises the question whether they could enable the design of dialyzers with improved PBUT clearance. Here, we develop device-level and multi-compartment (body) system-level models that account for PBUT-albumin binding (specifically indoxyl sulfate and p-cresyl sulfate) and diffusive and convective transport of toxins to investigate how the overall membrane permeance (or area) and system parameters including flow rates and ultrafiltration affect PBUT clearance in hemodialysis. Our simulation results indicate that, in contrast to urea clearance, PBUT clearance in current dialyzers is mass-transfer limited: Assuming that the membrane resistance is dominant, raising PBUT permeance from 3 × 10-6 to 10-5 m s-1 (or equivalently, 3.3 × increase in membrane area from ~ 2 to ~ 6 m2) increases PBUT removal by 48% (from 22 to 33%, i.e., ~ 0.15 to ~ 0.22 g per session), whereas increasing dialysate flow rates or adding adsorptive species have no substantial impact on PBUT removal unless permeance is above ~ 10-5 m s-1. Our results guide the future development of membranes, dialyzers, and operational parameters that could enhance PBUT clearance and improve patient outcomes.

Latest Trends in Hemodiafiltration

This review provides a detailed analysis of hemodiafiltration (HDF), its progress from an emerging technique to a potential conventional treatment for chronic hemodialysis patients, and its current status. The article covers the advances, methods, and clinical benefits of HDF, specifically focusing on its impact on cardiovascular health, survival rates, and overall well-being. The review also addresses questions about the safety of HDF and provides evidence to dispel concerns related to the elimination of beneficial substances and infection risks. Additionally, the article explores the potential implications of expanded hemodialysis (HDx) as an alternative to HDF, its classification, safety profile, and an ongoing trial assessing its non-inferiority to HDF. Supported by evidence from randomized controlled trials and observational studies, the review emphasizes the superiority of HDF as a hemodialysis modality and advocates for its positioning as the gold standard in treatment. However, it acknowledges the need for extensive research to define the role of HDx in comprehensive treatment approaches in individuals undergoing dialysis. The synthesis of current knowledge underscores the importance of ongoing exploration and research to refine hemodialysis practices for optimal patient outcomes.

Comparing Survival Outcomes between Hemodialysis and Hemodiafiltration Using Real-World Data from Brazil

The CONVINCE trial demonstrates that high-dose hemodiafiltration offers a survival advantage for patients in the high-flux hemodiafiltration group compared to hemodialysis. We compared the outcomes of hemodialysis and hemodiafiltration using real-world data. We conducted an analysis on a cohort of patients who underwent hemodiafiltration therapy (HDF) at a single center, NefroStar Clinics. The results obtained were then compared with data from patients receiving hemodialysis (HD) therapy within the Brazilian Public Health System (SUS). The primary outcome was mortality from any cause. Results: A total of 85 patients undergoing hemodiafiltration were compared with 149,372 patients receiving hemodialysis through the Brazilian Public Health System (SUS). Using a 2:1 propensity score, we compared the 170 best-match HD patients with 85 HDF patients. In the Cox analysis, HDF therapy showed a reduced risk of mortality with an HR of 0.29 [0.11-0.77]. The propensity score analysis showed a HR of 0.32 [95% CI: 0.11-0.91]. This analysis was adjusted for age, type of access, KT/v, hemoglobin, and phosphorus. The Kaplan-Meier analysis showed respective survival rates for HDF and HD at the end of one year, 92.1% and 79.9%, p < 0.001. These results suggest high-flux hemodiafiltration has survival advantages over hemodialysis in a real-world scenario.

Removal performance of pre- and post-dilution online hemodiafiltration using identical hemodiafilters in the same patients

Online hemodiafiltration (OHDF) for renal replacement therapy has two modes: pre- (pre-OHDF) and post-dilution OHDF (post-OHDF). To elucidate the precise differences between the two modes, a clinical study was performed using the same polysulfone hemodiafilters in the same patients. Eight patients were treated with ABH™-22PA for 6 weeks: 3 weeks of pre-OHDF (with substitution volumes of 24, 36, and 48 L) and 3 weeks of post-OHDF (6, 8, and 10 L). The reduction ratios of urea, uric acid (UA), creatinine (CRE), inorganic phosphorus (iP), beta-2-microglobulin (β2-MG), and alpha-1-microglobulin (α1-MG) were evaluated. The removal amounts of β2-MG, α1-MG, and albumin were also evaluated by analyzing the spent dialysis fluids. The types and numbers of adverse events (AEs) and device malfunctions were recorded. The reduction ratios of urea, UA, CRE, iP, and β2-MG were comparable among all conditions, while that of α1-MG tended to be slightly higher in post-OHDF than in pre-OHDF. The removal amounts of α1-MG and albumin in pre-OHDF and post-OHDF were significantly greater with the maximum substitution volume than with the minimum volume. However, the selective removal indices, which were obtained by dividing the amount of α1-MG removed by the albumin level, tended to be slightly higher in pre- than in post-OHDF. No device-related AEs or device malfunctions occurred in either mode. No significant differences in inflammatory responses, evaluated by high-sensitivity C-reactive protein and interleukin-6, were observed. This study provides removal performance and safety data regarding the application of ABH-22PA for pre- and post-OHDF.

Unveiling the Clinical Benefits of High-Volume Hemodiafiltration: Optimizing the Removal of Medium-Weight Uremic Toxins and Beyond

Dialysis treatment has improved the survival of patients with kidney failure. However, the hospitalization and mortality rates remain alarmingly high, primarily due to incomplete uremic toxin elimination. High-volume hemodiafiltration (HDF) has emerged as a promising approach that significantly improves patient outcomes by effectively eliminating medium and large uremic toxins, which explains its increasing adoption, particularly in Europe and Japan. Interest in this therapy has grown following the findings of the recently published CONVINCE study, as well as the need to understand the mechanisms behind the benefits. This comprehensive review aims to enhance the scientific understanding by explaining the underlying physiological mechanisms that contribute to the positive effects of HDF in terms of short-term benefits, like hemodynamic tolerance and cardiovascular disease. Additionally, it explores the rationale behind the medium-term clinical benefits, including phosphorus removal, the modulation of inflammation and oxidative stress, anemia management, immune response modulation, nutritional effects, the mitigation of bone disorders, neuropathy relief, and amyloidosis reduction. This review also analyzes the impact of HDF on patient-reported outcomes and mortality. Considering the importance of applying personalized uremic toxin removal strategies tailored to the unique needs of each patient, high-volume HDF appears to be the most effective treatment to date for patients with renal failure. This justifies the need to prioritize its application in clinical practice, initially focusing on the groups with the greatest potential benefits and subsequently extending its use to a larger number of patients.

Lower accuracy of testosterone, cortisol, and free T4 measurements using automated immunoassays in people undergoing hemodialysis

OBJECTIVES

Hormone measurements using automated immunoassays (IAs) can be affected by the sample matrix. Liquid chromatography tandem-mass spectrometry (LC-MS/MS) is less affected by these matrix effects. In clinical laboratories, testosterone, cortisol and, free thyroxine (FT4) are often measured using IAs. Renal failure alters serum composition in blood samples from people undergoing hemodialysis (HDp) and have, therefore, a complex serum constitution compared to healthy controls (HC). The goal of this study was to investigate the accuracy of testosterone, cortisol, and FT4 measurements in samples of HDp and to get more insight in the interfering factors.

METHODS

Thirty serum samples from HDp and HC were collected to measure testosterone, cortisol, and FT4 using a well standardized isotope dilution (ID)-LC-MS/MS method and 5 commercially available automated IAs (Alinity, Atellica, Cobas, Lumipulse, UniCel DXI). Method comparisons between LC-MS/MS and IAs were performed using both HDp and HC samples.

RESULTS

Average bias from the LC-MS/MS was for testosterone, cortisol, and FT4 immunoassays respectively up to 92, 7-47 and 16-27% more in HDp than in HC samples and was IA dependent. FT4 IA results were falsely decreased in HDp samples, whereas cortisol and testosterone concentrations in females were predominantly falsely increased. Correlation coefficients between LC-MS/MS and IA results were lower in HDp compared to HC samples.

CONCLUSIONS

Several IAs for testosterone (in women), cortisol, and FT4 are less reliable in the altered serum matrix of samples of HDp than in HC. Medical and laboratory specialists should be aware of these pitfalls in this specific population.

Comparative Clinical Performances of Tunneled Central Venous Catheters versus Arterio-Venous Accesses in Patients Receiving High-Volume Hemodiafiltration: The Case for High-Flow DualCath, a Tunneled Two-Single-Lumen Silicone Catheter

Tunneled central venous catheters (CVC) are mainly considered as a rescue vascular access option in dialysis but are still used on approximately one quarter of prevalent patients worldwide even though they are associated with poor performances and higher risks.

STUDY DESIGN

in this retrospective single-center study, we aimed to report on the clinical performances achieved with high-flow tunneled CVCs (DualCath or DCath) and compared them with arteriovenous accesses (AVAs, e.g., AV fistula, AV graft, and Thomas Shunt) in a hospital-based dialysis unit.

METHODS

Sixty-eight stage 5 chronic kidney disease dialysis-dependent patients (CKD5D) receiving high volume hemodiafiltration were followed-up with for 30 months. The study consisted of two phases: baseline cross-sectional and longitudinal follow-ups of key performance indicators. Clinical performances consisting of effective blood flow and blood volume, recirculation, urea and ionic Kt/V, total Kt, ultrafiltration volume, and percent reduction in β2-M were measured monthly as part of quality control in our unit.

RESULTS

At baseline, the effective blood flow using a DCath was close to 400 mL/min, similar to an AVA. Recirculation with a DCath (7%, 6-13%) was higher than with an AVA. The diffusive dialysis dose delivered with a DCath (spKt and eKt/V) and convective dialysis dose achieved with a DCath were slightly lower than those achieved with AVAs, but they were still much higher than is recommended by guidelines. The percent reduction in β2-M achieved with a DCath was also 4 to 10% lower than that achieved with an AVA. On longitudinal follow-up, the main clinical performance indicators of DCaths (total Kt and total ultrafiltration volume, L/session) were maintained as very stable over time and close to those achieved with AVAs.

CONCLUSIONS

As shown in this study, high-flow DualCath tunneled two-single-lumen silicone catheters may be used to deliver high volume hemodiafiltration in a reliable and consistent manner without compromising clinical performance. These results relied on the specific design of the two silicone cannulas and the strict adherence to best catheter practices.

Switching from continuous veno-venous hemodiafiltration to intermittent sustained low-efficiency daily hemodiafiltration (SLED-f) in pediatric acute kidney injury: A prospective cohort study

INTRODUCTION

Continuous kidney replacement therapy (CKRT) is the preferred modality in critically ill children with acute kidney injury. Upon improvement, intermittent hemodialysis is usually initiated as a step-down therapy, which can be associated with several adverse events. Hybrid therapies such as Sustained low-efficiency daily dialysis with pre-filter replacement (SLED-f) combines the slow sustained features of a continuous treatment, ensuring hemodynamic stability, with similar solute clearance along with the cost effectiveness of conventional intermittent hemodialysis. We examined the feasibility of using SLED-f as a transition step-down therapy after CKRT in critically ill pediatric patients with acute kidney injury.

METHODS

A prospective cohort study was conducted in children admitted to our tertiary care pediatric intensive care units with multi-organ dysfunction syndrome including acute kidney injury who received CKRT for management. Those patients receiving fewer than two inotropes to maintain perfusion and failed a diuretic challenge were switched to SLED-f.

RESULTS

Eleven patients underwent 105 SLED-f sessions (mean of 9.55 +/- 4.90 sessions per patient), as a part of step-down therapy from continuous hemodiafiltration. All (100%) our patients had sepsis associated acute kidney injury with multiorgan dysfunction and required ventilation. During SLED-f, urea reduction ratio was 64.1 +/- 5.3%, Kt/V was 1.13 +/- 0.1, and beta-2 microglobulin reduction was 42.5 +/-4%. Incidence of hypotension and requirement of escalation of inotropes during SLED-f was 18.18%. Filter clotting occurred twice in one patient.

CONCLUSION

SLED-f is a safe and effective modality for use as a transition therapy between CKRT and intermittent hemodialysis in children in the PICU.

Correlation between nerve conduction changes and BETA-2 microglobulin concentration in chronic kidney disease patients on hemodialysis combined with hemodiafiltration online

This study aimed to investigate the correlation between beta-2 microglobulin (B2M) concentration and some nerve conduction indices and evaluate the changes in some nerve conduction indices after treatment with hemodialysis (HD) combined with hemodiafiltration online in end-stage renal disease patients. From July 2021 to July 2022, a cross-sectional study was conducted on 80 end-stage renal disease patients on HD at Can Tho General Hospital, Viet Nam. All the patients had B2M testing and nerve conduction measurements. Patients with nerve conduction disorders were treated and remeasured after 6 months to evaluate the treatment results. At baseline, there was a moderate negative correlation between B2M and the tibial nerve and motor branch of the ulnar conduction velocity (V) (r = -0.305 and -0.315, P < .05). There was a moderate positive correlation between B2M and motor latency of the tibial and peroneal nerve (r = 0.434 and 0.440, P < .05). After 6 months of using the combination of HD and hemodiafiltration online, the V (31.3 ± 7.96 up to 44.88 ± 9.67 m/s) and the amplitude (A) (1.71 ± 1.16 up to 2.61 ± 1.51 mV) of the peroneal nerve increased, the motor latency decreased (8.21 ± 2.65 down to 5.23 ± 3.58 ms). With the tibial nerve, motor conduction V increased from 30.53 ± 8.05 m/s to 43.56 ± 8.99 m/s and the A increased from 5.04 ± 3.16 mV to 7.75 ± 4.45 mV. With the ulnar nerve, the A increased, and motor latency decreased after 6 months. The nerve conduction indices also improved significantly in the median nerve.

Impact of needle type on substitution volume during online hemodiafiltration: plastic cannulae versus metal needles

BACKGROUND

Plastic cannulae have attracted increasing interest as an alternative to traditional metal needles with the aim of reducing cannulation-related complications. We investigated whether the substitution volumes during hemodiafiltration differ using these two types of needles in dialysis patients.

METHODS

An intervention study involving 26 hemodialysis patients was conducted in Korea between March and September in 2021. Patients first received online hemodiafiltration using traditional metal needles, and thereafter plastic cannulae were used in a stepwise protocol. Repeated-measures design and linear mixed-effect models were used to compare substitution volumes between the two needle types with the same inner diameter.

RESULTS

The mean patient age was 62.7 years, and their mean dialysis vintage was 95.2 months. Most patients (92.3%) had an arteriovenous fistula as the vascular access. The substitution volume increased as blood flow and needle size increased for both plastic cannulae and metal needles. The substitution volume was significantly higher with 17-gauge (G) plastic cannulae than with 16-G metal needles at blood flow rates of 280, 300, and 330 mL/min. Similar results were obtained for 15-G metal needles and 16-G plastic cannulae at a blood flow rate of 330 mL/min. However, the patient ratings of pain on a visual analogue scale were higher for plastic cannulae.

CONCLUSION

Higher substitution volumes were obtained at the same prescribed blood flow rate with plastic cannulae than with metal needles during online hemodiafiltration. Plastic cannulae are an option for achieving high-volume hemodiafiltration for patients with low blood flow rates.

Nutritional and Anthropometric Indices in Children Receiving Haemodiafiltration vs Conventional Haemodialysis - The HDF, Heart and Height (3H) Study

BACKGROUND

The "HDF-Heart-Height" study showed that haemodiafiltration (HDF) is associated with improved growth compared to conventional haemodialysis (HD). We report a post-hoc analysis of this study assessing the effect of extracorporeal dialysis therapies on nutritional indices.

METHODS

107 children were included in the baseline cross-sectional analysis, of whom 79 (43 HD, 36 HDF) completed the 12-month follow-up. Height (Ht), optimal 'dry' weight (Wt), and body mass index (BMI) standard deviations scores (SDS), waist-to-hip ratio, des-acyl ghrelin (DAG), adiponectin, leptin, insulin-like growth factor-1 (IGF-1)-SDS and insulin were measured.

RESULTS

The levels of nutritional indices were comparable between HDF and HD patients at baseline and 12-month. On univariable analyses Wt-SDS positively correlated with leptin and IGF-1-SDS, and negatively with DAG, while Ht-SDS of the overall cohort positively correlated with IGF1-SDS and inversely with DAG and adiponectin. On multivariable analyses, higher 12-month Ht-SDS was inversely associated with baseline DAG (beta = -0.13 per 500 higher; 95%CI -0.22, -0.04; P = .004). Higher Wt-SDS at 12-month was positively associated with HDF modality (beta = 0.47 vs HD; 95%CI 0.12-0.83; P = .01) and inversely with baseline DAG (beta = -0.18 per 500 higher; 95%CI -0.32, -0.05; P = .006). Growth Hormone (GH) treated patients receiving HDF had higher annualized increase in Ht SDS compared to those on HD.

CONCLUSIONS

In children on HD and HDF both Wt- and Ht-SDS independently correlated with lower baseline levels of the anorexygenic hormone DAG. HDF may attenuate the resistance to GH, but further studies are required to examine the mechanisms linking HDF to improved growth.

Assessment of the Influence of Asymmetric Triacetate Cellulose Membrane on the Rate of Removal of Middle Molecular Weight Uremic Toxins in Patients Treated with Postdilution Online Hemodiafiltration

BACKGROUND: Postdilution online hemodiafiltration (OL-HDF) effectively removes uremic toxins of middle molecular weight from the blood of patients with end-stage chronic kidney disease. The rate of removal of uremic toxins depends on the type of dialysis membrane, blood flow rate (Qb), net ultrafiltration flow rate (Qnuf), and total convective volume (Vconv). AIM: The aim of this study was to examine the efficacy of asymmetric triacetate cellulose dialysis membrane in patients on post-dilution OL-HDF. METHODS: Thirty-five patients treated with post-dilution OL-HDF hemodiafiltration for at least 3 months were examined. The main parameters for assessing the efficiency of removal of uremic toxins of middle molecular weight are the concentration of β2-microglobulin (β2-M) and interleukin-6 (IL-6) in serum before and after a single session of post-dilution OL-HDF. The followings were used for statistical analysis: Kolmogorov–Smirnov test, Student’s T test for bound samples and Wilcoxon test. RESULTS: The average Vconv was 20.90 ± 3.30 liters/session. The β2-M reduction index during a single session of postdilution OL-HDF was 71.10 ± 6.39%, the IL-6 reduction index was 43.75 ± 15.60%, and the albumin reduction index was 4.55 ± 2.31%. CONCLUSION: The asymmetric triacetate cellulose dialysis membrane effectively removes β2-M and IL-6 during a single session of postdilution OL-HDF. The β2-M reduction index is ∼70%, the IL-6 reduction index is ∼40%, and albumin loss is <4.0 g/4 h. The examined dialysis membrane and dialysis modality prevent the development of amyloidosis associated with dialysis, microinflammation and reduce the risk of developing atherosclerotic cardiovascular diseases in the population of patients treated with regular hemodiafiltration.

Comparison of measured vs kinetic-model predicted phosphate removal during hemodialysis and hemodiafiltration

BACKGROUND

To what extent hemodiafiltration (HDF) improves management of hyperphosphatemia over hemodialysis (HD) is a subject of ongoing investigation.

METHODS

We modified a previously described phosphate kinetic model to include incorporation of EUDIAL recommended equations for hemodiafiltration (HDF) clearance. We used the model to predict the recovery of phosphate from spent dialysate/hemofiltrate and compared this with averaged data from five published studies. Mean study average predialysis serum phosphate was 1.81 ± 0.20 mmol/L. Session length was close to 240 min per treatment. All HDF was done postdilution, at an average rate of 65 ± 24 mL/min.

RESULTS

Measured mean phosphate removal was 1039 ± 136 mg (33.5 ± 4.41 mmol, slightly lower than the model-predicted mean value of 1092 ± 127 mg (35.3 ± 4.09 mmol). The measured ratio of phosphate removal with HDF compared with HD averaged 1.15 ± 0.22, ranging from 1.01 to 1.44. Using mean study input parameters for patient size and treatment characteristics, the predicted ratio of phosphate removal with HDF compared with HD averaged 1.095 ± 0.029, ranging from 1.05 to 1.13.

CONCLUSIONS

Addition of EUDIAL-recommended convective clearance equations to a phosphate kinetic model predicts a 10% or greater benefit in terms of phosphate removal for HDF compared with HD at typical dialysis and hemodiafiltration treatment settings. These predictions are similar to the HDF advantage reported in the literature in studies where phosphate removal has been measured in spent dialysate.

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.

The high-volume haemodiafiltration vs high-flux haemodialysis registry trial (H4RT): a multi-centre, unblinded, randomised, parallel-group, superiority study to compare the effectiveness and cost-effectiveness of high-volume haemodiafiltration and high-flux haemodialysis in people with kidney failure on maintenance dialysis using linkage to routine healthcare databases for outcomes

BACKGROUND

More than a third of the 65,000 people living with kidney failure in the UK attend a dialysis unit 2-5 times a week to have their blood cleaned for 3-5 h. In haemodialysis (HD), toxins are removed by diffusion, which can be enhanced using a high-flux dialyser. This can be augmented with convection, as occurs in haemodiafiltration (HDF), and improved outcomes have been reported in people who are able to achieve high volumes of convection. This study compares the clinical- and cost-effectiveness of high-volume HDF compared with high-flux HD in the treatment of kidney failure.

METHODS

This is a UK-based, multi-centre, non-blinded randomised controlled trial. Adult patients already receiving HD or HDF will be randomised 1:1 to high-volume HDF (aiming for 21+ L of substitution fluid adjusted for body surface area) or high-flux HD. Exclusion criteria include lack of capacity to consent, life expectancy less than 3 months, on HD/HDF for less than 4 weeks, planned living kidney donor transplant or home dialysis scheduled within 3 months, prior intolerance of HDF and not suitable for high-volume HDF for other clinical reasons. The primary outcome is a composite of non-cancer mortality or hospital admission with a cardiovascular event or infection during follow-up (minimum 32 months, maximum 91 months) determined from routine data. Secondary outcomes include all-cause mortality, cardiovascular- and infection-related morbidity and mortality, health-related quality of life, cost-effectiveness and environmental impact. Baseline data will be collected by research personnel on-site. Follow-up data will be collected by linkage to routine healthcare databases - Hospital Episode Statistics, Civil Registration, Public Health England and the UK Renal Registry (UKRR) in England, and equivalent databases in Scotland and Wales, as necessary - and centrally administered patient-completed questionnaires. In addition, research personnel on-site will monitor for adverse events and collect data on adherence to the protocol (monthly during recruitment and quarterly during follow-up).

DISCUSSION

This study will provide evidence of the effectiveness and cost-effectiveness of HD as compared to HDF for adults with kidney failure in-centre HD or HDF. It will inform management for this patient group in the UK and internationally.

TRIAL REGISTRATION

ISRCTN10997319 . Registered on 10 October 2017.

Personalizing treatment in end-stage kidney disease: deciding between hemodiafiltration and hemodialysis based on individualized treatment effect prediction

Background

Previous studies suggest that hemodiafiltration reduces mortality compared to hemodialysis in patients with end-stage kidney disease (ESKD), but controversy surrounding its benefits remain and it is unclear to what extent individual patients benefit from hemodiafiltration. This study aimed to develop and validate a treatment effect prediction model to determine which patients would benefit most from hemodiafiltration compared to hemodialysis in terms of all-cause mortality.

Methods

Individual participant data from four randomized controlled trials comparing hemodiafiltration with hemodialysis on mortality were used to derive a Royston-Parmar model for prediction of absolute treatment effect of hemodiafiltration based on pre-specified patient and disease characteristics. Validation of the model was performed using internal-external cross validation.

Results

The median predicted survival benefit was 44 (Q1-Q3: 44–46) days for every year of treatment with hemodiafiltration compared to hemodialysis. The median survival benefit with hemodiafiltration ranged from 2 to 48 months. Patients who benefited most from hemodiafiltration were younger, less likely to have diabetes or a cardiovascular history and had higher serum creatinine and albumin levels. Internal-external cross validation showed adequate discrimination and calibration.

Conclusion

Although overall mortality is reduced by hemodiafiltration compared to hemodialysis in ESKD patients, the absolute survival benefit can vary greatly between individuals. Our results indicate that the effects of hemodiafiltration on survival can be predicted using a combination of readily available patient and disease characteristics, which could guide shared decision-making.

Semi-Quantitative Evaluation of Asymmetricity of Dialysis Membrane Using Forward and Backward Ultrafiltration

Performance of the dialysis membrane is strongly dependent upon the physicochemical structure of the membrane. The objective of this study is to devise a new in vitro evaluation technique to quantify the physicochemical structures of the membrane. Three commercial dialyzers with cellulose triacetate (CTA), asymmetric CTA (termed ATA^®), and polyether sulfone (PES) membranes (Nipro Co., Osaka, Japan) were employed for investigation. Forward and backward ultrafiltration experiments were performed separately with aqueous vitamin B₁₂ (MW 1355), α-chymotrypsin (MW 25,000), albumin (MW 66,000) and dextran solutions, introducing the test solution inside or outside the hollow fiber (HF), respectively. Sieving coefficients (s.c.) for these solutes were measured under the test solution flow rate of 200 mL/min and the ultrafiltration rate of 10 mL/min at 310 K, according to the guidelines provided by Japanese academic societies. We defined the ratio of s.c. in the backward ultrafiltration to that in the forward ultrafiltration and termed it the index for asymmetricity (IA). The IA values were unity for vitamin B₁₂ and α-chymotrypsin in all three of the dialyzers. The IA values for albumin, however, were 1.0 in CTA, 1.9 in ATA^®, and 3.9 in PES membranes, respectively, which corresponded well with the fact that CTA is homogeneous, whereas ATA^® and PES are asymmetrical in structure. Moreover, the asymmetricity of ATA^® and PES may be different by twofold. This fact was verified in continuous basis by employing dextran solution before and after being fouled with albumin. These findings may contribute to the development of a novel membrane for improved success of dialysis therapy.

Prescription of online hemodiafiltration (ol-HDF)

HDF prescription should be able to satisfy the delivery of an optimal dialytic convective dose. Several factors are implicated in this endeavor. High blood flow rate is crucial to warranty processing an adequate blood volume and to ensure the highest shear rate per fiber needed to cleanse and prevent membrane fouling. A highly permeable dialyzer is needed with a surface area aligned to blood flow and performance needs. Anticoagulation requires specific adaptation in case of low molecular weight heparin use. By default, HDF prescription modality should ideally start by postdilution mode with a stepwise increment of convective dose by probing patient tolerance and efficacy. Alternative substitution modality should be considered if dialytic convective dose could not be achieved in the usual time frame. Convective dose prescription relies either on a manual mode (pressure control or volume control) or on automated mode (ultrafiltration control) depending on the technical options of the HDF machines. Dialysate flow rate is regulated by the HDF machine but should preferably keep constant dialysis fluid flowing the dialyzer with a Qb:Qd ratio of 1.4. Treatment time should not be reduced with HDF prescription. Treatment time should fit with patient tolerance (hemodynamic, osmotic, and solute shifts) and overall solute removal efficiency. Electrolytic prescription does not require specific adjustments as compared with conventional dialysis, but the patient needs to be monitored regularly and dialysate electrolyte adjusted to lab tests. A stepwise approach for implementing ol-HDF is preferable depending on the initial condition of the patient. Three particular cases may be considered: late-stage chronic kidney disease patient transitioning to renal replacement therapy, stable dialysis patient switching to HDF, and unstable or fragile patient or specific treatment schedule. Optimal dosing of HDF and personalized care to ensure treatment adequacy is the main goal for renal replacement therapy to improve patient outcomes. That should be ensured with HDF treatment.

Mass Transport in High-Flux Hemodialysis: Application of Engineering Principles to Clinical Prescription

An understanding of the processes underlying mass transfer is paramount for the attainment of adequate solute removal in the dialytic treatment of patients with kidney failure. In this review, engineering principles are applied to characterize the physical mechanisms behind the two major modes of mass transfer during hemodialysis, namely diffusion and convection. The manner in which flow rate, dialyzer geometry, and membrane microstructure affect these processes is discussed, with concepts such as boundary layers, effective membrane diffusivity, and sieving coefficients highlighted as critical considerations. The objective is to improve clinicians' understanding of these concepts as important factors influencing the prescription and delivery of hemodialysis therapy.

CONVINCE in the context of existing evidence on haemodiafiltration

Haemodiafiltration (HDF) provides a greater removal of larger solutes and protein-bound compounds than conventional high-flux haemodialysis (HD). There are indications that the patients receiving the highest convection volumes of HDF result in an improved survival compared with HD. However, the comparative efficacy of HDF vs HD remains unproven. Here we provide a comparative account of the methodology and aims of ‘the comparison of high-dose HDF with high-flux HD’ (CONVINCE) study in the context of the totality of evidence and how this study will contribute to reaching a higher level of certainty regarding the comparative efficacy of HDF vs HD in people with end-stage kidney disease (ESKD).

Does delivering more dialysis improve clinical outcomes? What randomized controlled trials have shown

Some randomized controlled trials (RCTs) have sought to determine whether different dialysis techniques, dialysis doses and frequencies of treatment are able to improve clinical outcomes in end-stage kidney disease (ESKD). Virtually all of these RCTs were enacted on the premise that 'more' haemodialysis might improve clinical outcomes compared to 'conventional' haemodialysis. Aim of the present narrative review was to analyse these landmark RCTs by posing the following question: were their intervention strategies (i.e., earlier dialysis start, higher haemodialysis dose, intensive haemodialysis, increase in convective transport, starting haemodialysis with three sessions per week) able to improve clinical outcomes? The answer is no. There are at least two main reasons why many RCTs have failed to demonstrate the expected benefits thus far: (1) in general, RCTs included relatively small cohorts and short follow-ups, thus producing low event rates and limited statistical power; (2) the designs of these studies did not take into account that ESKD does not result from a single disease entity: it is a collection of different diseases and subtypes of kidney dysfunction. Patients with advanced kidney failure requiring dialysis treatment differ on a multitude of levels including residual kidney function, biochemical parameters (e.g., acid base balance, serum electrolytes, mineral and bone disorder), and volume overload. In conclusion, the different intervention strategies of the RCTs herein reviewed were not able to improve clinical outcomes of ESKD patients. Higher quality studies are needed to guide patients and clinicians in the decision-making process. Future RCTs should account for the heterogeneity of patients when considering inclusion/exclusion criteria and study design, and should a priori consider subgroup analyses to highlight specific subgroups that can benefit most from a particular intervention.

Flummoxed by flux: the indeterminate principles of haemodialysis

In haemodialysis (HD), unwanted substances (uraemic retention solutes or ‘uraemic toxins’) that accumulate in uraemia are removed from blood by transport across the semipermeable membrane. Like all membrane separation processes, the transport requires driving forces to facilitate the transfer of molecules across the membrane. The magnitude of the transport is quantified by the phenomenon of ‘flux’, a finite parameter defined as the volume of fluid (or permeate) transferred per unit area of membrane surface per unit time. In HD, as transmembrane pressure is applied to facilitate fluid flow or flux across the membrane to enhance solute removal, flux is defined by the ultrafiltration coefficient (KUF; mL/h/mmHg) reflecting the hydraulic permeability of the membrane. However, in HD, the designation of flux has come to be used in a much broader sense and the term is commonly used interchangeably and erroneously with other measures of membrane separation processes, resulting in considerable confusion. Increased flux is perceived to reflect more ‘porous’ membranes having ‘larger’ pores, even though other membrane and therapy attributes determine the magnitude of flux achieved during HD. Adjectival designations of flux (low-, mid-, high-, super-, ultra-) have found indiscriminate usage in the scientific literature to qualify a parameter that influences clinical decision making and prescription of therapy modalities (low-flux or high-flux HD). Over the years the concept and definition of flux has undergone arbitrary and periodic adjustment and redefinition by authors in publications, regulatory bodies (US Food and Drug Administration) and professional association guidelines (European Renal Association, Kidney Disease Outcomes Quality Initiative), with little consensus. Industry has stretched the boundaries of flux to derive marketing advantages, justify increased reimbursement or contrive new classes of therapy modalities when in fact flux is just one of several specifications that determine membrane or dialyser performance. Membranes considered as high-flux previously are today at the lower end of the flux spectrum. Further, additional parameters unrelated to the rate of diffusive or convective transport (flux) are used in conjunction with or in place of KUF to allude to flux: clearance (mL/min, e.g. of β₂-microglobulin) or sieving coefficients (dimensionless). Considering that clinical trials in nephrology, designed to make therapy recommendations and guide policy with economic repercussions, are based on the parameter flux they merit clarification—by regulatory authorities and scientists alike—to avoid further misappropriation.

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.

Choices in hemodialysis therapies: variants, personalized therapy and application of evidence-based medicine

The extent of removal of the uremic toxins in hemodialysis (HD) therapies depends primarily on the dialysis membrane characteristics and the solute transport mechanisms involved. While designation of ‘flux’ of membranes as well toxicity of compounds that need to be targeted for removal remain unresolved issues, the relative role, efficiency and utilization of solute removal principles to optimize HD treatment are better delineated. Through the combination and intensity of diffusive and convective removal forces, levels of concentrations of a broad spectrum of uremic toxins can be lowered significantly and successfully. Extended clinical experience as well as data from several clinical trials attest to the benefits of convection-based HD treatment modalities. However, the mode of delivery of HD can further enhance the effectiveness of therapies. Other than treatment time, frequency and location that offer clinical benefits and increase patient well-being, treatment- and patient-specific criteria may be tailored for the therapy delivered: electrolytic composition, dialysate buffer and concentration and choice of anticoagulating agent are crucial for dialysis tolerance and efficacy. Evidence-based medicine (EBM) relies on three tenets, i.e. clinical expertise (i.e. doctor), patient-centered values (i.e. patient) and relevant scientific evidence (i.e. science), that have deviated from their initial aim and summarized to scientific evidence, leading to tyranny of randomized controlled trials. One must recognize that practice patterns as shown by Dialysis Outcomes and Practice Patterns Study and personalization of HD care are the main driving force for improving outcomes. Based on a combination of the three pillars of EBM, and particularly on bedside patient–clinician interaction, we summarize what we have learned over the last 6 decades in terms of best practices to improve outcomes in HD patients. Management of initiation of dialysis, vascular access, preservation of kidney function, selection of biocompatible dialysers and use of dialysis fluids of high microbiological purity to restrict inflammation are just some of the approaches where clinical experience is vital in the absence of definitive scientific evidence. Further, HD adequacy needs to be considered as a broad and multitarget approach covering not just the dose of dialysis provided, but meeting individual patient needs (e.g. fluid volume, acid–base, blood pressure, bone disease metabolism control) through regular assessment—and adjustment—of a series of indicators of treatment efficiency. Finally, in whichever way new technologies (i.e. artificial intelligence, connected health) are embraced in the future to improve the delivery of dialysis, the human dimension of the patient–doctor interaction is irreplaceable. Kidney medicine should remain ‘an art’ and will never be just ‘a science’.

Intraocular Pressure Changes during Hemodiafiltration with Two different Concentrations of Sodium in the Dialysate

Simple Summary

An increase in intraocular pressure during chronic hemodialysis is linked to ocular complications, such as glaucoma. The behavior of intraocular pressure during hemodiafiltration is unknown. Changes in intraocular pressure with a sodium dialysate concentration fixed at 138 mmol/L and an individualized concentration were studied in 13 patients with end-stage renal disease treated with hemodiafiltration. Up to 31% patients presented an episode of intraocular hypertension without differences between sodium profiles. A large variability in intraocular pressure within patients and a high prevalence of transient intraocular hypertension were found.

Abstract

Ocular complications are common among end-stage renal disease patients and some complications had been linked to increments of intraocular pressure (IOP) during hemodialysis. The changes of IOP during hemodiafiltration (HDF) have been scarcely investigated and the potential influence of the sodium dialysate concentration is unknown. The aim of this study was to compare the IOP changes during HDF with sodium dialysate concentration, either fixed or individualized. Thirteen end-stage renal disease patients participated in the study; they were treated with HDF using a dialysate sodium profile fixed at 138 mmol and another session with an individualized sodium profile. The intraocular pressure was measured before and after each session and every 30 min during HDF. Both groups had a similar HDF prescription, blood pressure, and biochemical parameters. At the end of hemodiafiltration, sodium concentration decreased only in the fixed sodium profile group. The number of patients with at least an episode of intraocular hypertension during HDF ranged from 5 (19%) to 8 (31%) without significant differences between right and left eye nor between dialysate sodium concentration. During HDF, there is a large variability of IOP; transient events of intraocular hypertension are highly prevalent in this sample, and they are not related to the sodium dialysate concentration.

Mixed versus predilution hemodiafiltration effects on convection volume and small and middle molecule clearance in hemodialysis patients: a prospective randomized controlled trial

Background

The use of newly developed mixed-dilution hemodiafiltration (HDF) can supplement the weaknesses of pre- and postdilution HDF. However, it is unclear whether mixed-HDF performs well compared to predilution HDF.

Methods

We conducted a prospective, open-labeled, randomized controlled trial from two hemodialysis centers in Korea. Between January 2017 and September 2019, 60 patients who underwent chronic hemodialysis were randomly assigned at a 1:1 ratio to receive either predilution HDF (n = 30) or mixed-HDF (n = 30) for 6 months. We compared convection volume, changes in small- and medium-sized molecule clearance, high-sensitive C-reactive protein (hs-CRP) level, and dialysis-related parameters between the two dialysis modalities.

Results

A mean effective convection volume of 41.0 ± 10.3 L/session in the predilution HDF group and 51.5 ± 9.0 L/session in the mixed-HDF group was obtained by averaging values of three time-points. The difference in effective convection volume between the groups was 10.5 ± 1.3 L/session. This met the preset noninferiority criteria, suggesting that mixed-HDF was noninferior to predilution HDF. Moreover, the β2-microglobulin reduction rate was greater in the mixed-HDF group than in the predilution HDF group, while mixed-HDF provided greater transmembrane pressure. There were no significant between-group differences in Kt/V urea levels, changes in predialysis hs-CRP levels, proportions of overhydration, or blood pressure values. Symptomatic intradialytic hypotension episodes and other adverse events occurred similarly in the two groups.

Conclusion

Use of mixed-HDF was comparable to predilution HDF in terms of delivered convection volume and clinical parameters. Moreover, mixed-HDF provided better β2-microglobulin clearance than predilution HDF.

Reliable fluid-mechanical characterization of haemofilters: Addressing the deficiencies of current standards and practices

Facile methods for accurate fluid-mechanical characterization of haemofilters (HF) are indispensable for haemofiltration process improvements, equipment design/optimization, and reliable module specifications. Currently employed methods, implemented through specific experimental in vitro protocols, are assessed herein in detail, considering the conditions prevailing during haemofiltration. Minimum number of key parameters required to fully describe the common countercurrent flow field, in the HF active section, include membrane permeance K and friction coefficients in lumen and shell side (f_f and f_s ). It is shown that the countercurrent flow mode itself is incapable of yielding these parameters, based on externally measured flow rates and pressures. Similarly, the relevant ISO protocol is deficient as it can only provide rough underpredictions of permeance K. The causes of such inherent deficiencies of current standards and practices are analyzed. In contrast, a recently developed methodology, accounting for the (heretofore ignored) pressure drop in module headers and combining a mechanistic theoretical model with experimental data from 2 special haemofilter operating modes, yields an accurate determination of the key parameters (K, f_f , f_s ). Additionally, it permits a full description of flow field for Newtonian liquids, for both constant and axially varying viscosity in fiber-lumen due to the transmembrane flux. Development of new reliable standards is suggested, facilitated by the insights gained in this work.

Intermittent Convective Therapies in Patients with Acute Kidney Injury: A Systematic Review with Meta-Analysis

INTRODUCTION

In critically ill patients requiring intermittent renal replacement therapy (RRT), the benefits of convective versus diffusive clearance remain uncertain. We conducted a systematic review and meta-analysis to determine the safety, clinical efficacy, and clearance efficiency of hemofiltration (HF) and hemodiafiltration (HDF) compared to hemodialysis (HD) in patients with acute kidney injury (AKI) receiving intermittent RRT.

METHOD

We searched Medline, Embase, Cochrane Library, and PROSPERO. We included clinical trials and observational studies that reported the use of intermittent HF or HDF in adult patients with AKI. The following outcomes were included: mortality, renal recovery, clearance efficacy, intradialytic hemodynamic stability, circuit loss, and inflammation modulation.

RESULTS

A total of 3,169 studies were retrieved and screened. Four randomized controlled trials and 4 observational studies were included (n: 615 patients). Compared with conventional HD, intermittent convective therapies had no effect on in-hospital mortality (relative risk, 1.23; 95% confidence interval (CI), 0.76-1.99), renal recovery at 30 days (RR, 0.98; 95% CI, 0.82-1.16), time-to-renal recovery (mean difference [MD], 0.77; 95% CI, -6.56 to 8.10), and number of dialysis sessions until renal recovery (MD, -1.34; 95% CI, -3.39 to 0.72). The overall quality of included studies was low, and dialysis parameters were suboptimal for all included studies.

CONCLUSION

This meta-analysis suggests that there is no significant difference in short-term mortality and renal recovery in patients with severe AKI when treated with intermittent HF or HDF compared to conventional HD. This systematic review emphasizes the need for further trials evaluating optimal convective parameters in AKI patients treated with intermittent dialysis.