Achieving high convective volume in hemodiafiltration: Lessons learned after successful implementation in the HDFit trial

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.

High-Target Hemodiafiltration Convective Dose Achieved in Most Patients in a 6-Month Intermediary Analysis of the CONVINCE Randomized Controlled Trial

Introduction

High convection volumes in hemodiafiltration (HDF) result in improved survival; however, it remains unclear whether it is achievable in all patients.

Methods

CONVINCE, a randomized controlled trial, randomized patients with end-stage kidney disease 1:1 to high-dose HDF versus high-flux hemodialysis (HD) continuation. We evaluated the proportion of patients achieving high-dose HDF target: convection volume per visit of ≥23 l (range ±1 l) at baseline, month 3, and month 6. We compared baseline characteristics in the following 2 ways: (i) patients on target for all 3 visits versus patients who missed target on ≥1 visits and (ii) patients on target for all 3 visits or missing it once versus patients who missed target on ≥2 visits.

Results

A total of 653 patients were randomized to HDF. Their mean age was 62.2 (SD 13.5) years, 36% were female, 81% had fistula vascular access, and 33% had diabetes. Across the 3 visits, 75 patients (11%), 27 patients (4%), and 11 patients (2%) missed the convection volume target once, twice, and thrice, respectively. Apart from diabetes, there were no apparent differences in patient characteristics between patients who always achieved the high-dose target (83%) and those who missed the target either once or more (17%) or twice or more (6%).

Conclusion

Achieving high-dose HDF is feasible for nearly all patients in CONVINCE and could be maintained during the 6-month follow-up period. Apart from diabetes, there were no other indications for confounding by indication on multivariable analyses that may explain the potential survival advantage for patients receiving high-dose HDF.

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.

Effect of Hemodiafiltration or Hemodialysis on Mortality in Kidney Failure

BACKGROUND

Several studies have suggested that patients with kidney failure may benefit from high-dose hemodiafiltration as compared with standard hemodialysis. However, given the limitations of the various published studies, additional data are needed.

METHODS

We conducted a pragmatic, multinational, randomized, controlled trial involving patients with kidney failure who had received high-flux hemodialysis for at least 3 months. All the patients were deemed to be candidates for a convection volume of at least 23 liters per session (as required for high-dose hemodiafiltration) and were able to complete patient-reported outcome assessments. The patients were assigned to receive high-dose hemodiafiltration or continuation of conventional high-flux hemodialysis. The primary outcome was death from any cause. Key secondary outcomes were cause-specific death, a composite of fatal or nonfatal cardiovascular events, kidney transplantation, and recurrent all-cause or infection-related hospitalizations.

RESULTS

A total of 1360 patients underwent randomization: 683 to receive high-dose hemodiafiltration and 677 to receive high-flux hemodialysis. The median follow-up was 30 months (interquartile range, 27 to 38). The mean convection volume during the trial in the hemodiafiltration group was 25.3 liters per session. Death from any cause occurred in 118 patients (17.3%) in the hemodiafiltration group and in 148 patients (21.9%) in the hemodialysis group (hazard ratio, 0.77; 95% confidence interval, 0.65 to 0.93).

CONCLUSIONS

In patients with kidney failure resulting in kidney-replacement therapy, the use of high-dose hemodiafiltration resulted in a lower risk of death from any cause than conventional high-flux hemodialysis. (Funded by the European Commission Research and Innovation; CONVINCE Dutch Trial Register number, NTR7138.).

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.

Clinical performance, intermediate and long-term outcomes of high-volume hemodiafiltration in patients with kidney failure

Hemodiafiltration (HDF), in which both convective and diffusion methods are combined, yields an increased overall solute clearance compared with hemodialysis (HD), specifically for medium and larger molecular weight uremic toxins. Due to uncertainty in the treatment effects, the nephrology community still perceives the implementation of HDF and the achievement of high convective volume as complex. In this article, we review practical aspects of the implementation of HDF that can effectively deliver a high-volume HDF therapy and assure clinical performance to most patients. We also present an overview of the impact of high-volume HDF (compared to HD) on a series of relevant biochemical, patient-reported, and clinical outcomes, including uremic toxin removal, phosphate, Inflammation and oxidative stress, hemodynamic stability, cardiac outcomes, nutritional effects, health-related quality of life, morbidity, and mortality.

Hemodiafiltration in developing countries

Hemodiafiltration (HDF) is a promising kidney replacement therapy modality for patients with end-stage kidney disease. The principle of uremic toxin clearance by combining convection and diffusion can lead to greater benefits compared to conventional hemodialysis. Evidence is building that supports the advantages of HDF with short-term outcomes such as greater intradialytic hemodynamic stability, improved nutritional status, attenuation of anemia, and reduction of inflammatory cytokines which produce improved key long-term impacts including survival and cardiovascular outcomes. Very little is known about the prevalence of HDF treatments in developing countries due to a shortage of national kidney registries. HDF experience is limited in many countries due to the cost of dialysis treatments, availability of online HDF machines, and reimbursement policies. These obstacles have led to nephrologists developing innovations, for example, convective control HDF (CC-HDF), simple mid-dilution, and simple mixed-dilution methods, which may be as effective as commercially available HDF machines. In this article, we will focus on the experience of HDF practice and barriers to adoption in developing countries. Results can guide clinical practice recommendations for implementing HDF in resource-limited settings.

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.

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).

Why and how high volume hemodiafiltration may reduce cardiovascular mortality in stage 5 chronic kidney disease dialysis patients? A comprehensive literature review on mechanisms involved

Online hemodiafiltration (HDF) is an established renal replacement modality for patients with end stage chronic kidney disease that is now gaining rapid clinical acceptance worldwide. Currently, there is a growing body of evidence indicating that treatment with HDF is associated with better outcomes and reduced cardiovascular mortality for dialysis patients. In this comprehensive review, we provide an update on the potential mechanisms which may improve survival in HDF treated patients. The strongest evidence is for better hemodynamic stability and reduced endothelial dysfunction associated with HDF treatments. Clinically, this is marked by a reduced incidence of intradialytic hypotensive episodes, with a better hemodynamic response to ultrafiltration, mediated by an increase in total peripheral vascular resistance and extra-vascular fluid recruitment, most likely driven by the negative thermal balance associated with online HDF therapy. In addition, endothelial function appears to be improved due to a combination of a reduction of the inflammatory and oxidative stress complex syndrome and exposure to circulating cardiovascular uremic toxins. Reports of reversed cardiovascular remodeling effects with HDF may be confounded by volume and blood pressure management, which are strongly linked to center clinical practices. Currently, treatment with HDF appears to improve the survival of dialysis patients predominantly due to a reduction in their cardiovascular burden, and this reduction is linked to the sessional convection volume exchanged.