Clinical Evidence on Hemodiafiltration: A Systematic Review and a Meta-analysis

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.

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.

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.).

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.

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.

Comparison of four medium cut-off dialyzers

BACKGROUND

Recently, several pharmaceutical companies have developed new medium cut-off (MCO) dialyzers for expanded hemodialysis (HDx). This study aimed to compare the safety and efficacy of four MCO dialyzers, against each other and versus high-flux hemodialysis (HD) and post-dilution hemodiafiltration (HDF).

METHODS

A prospective study was carried out on 23 patients who underwent six dialysis sessions: two sessions with the FX80 Cordiax in HD and HDF, and four HDx sessions with the Phylther 17-SD, Vie-18X, Elisio HX19 and Theranova 400 dialyzers. The reduction ratios (RRs) of urea, creatinine, β2-microglobulin, myoglobin, kappa free immunoglobulin light chain (κFLC), prolactin, α1-microglobulin, α1-acid glycoprotein, lambda (λFLC) and albumin were compared. Dialysate albumin loss was also measured.

RESULTS

The differences in efficacy between the evaluated dialyzers were minimal in small molecules and even up to the size of β2-microglobulin. The main differences were found between myoglobin, κFLC, prolactin, α1-microglobulin and λFLC RRs, in which all four MCO dialyzers, with similar efficacy, were clearly superior to HD and slightly inferior to HDF treatment. Albumin losses in the dialysate with HD dialyzers were <1 g and between 1.5 and 2.5 g in HDx and HDF. The global removal score values were similar in all four HDx treatments, and again significantly higher than those with HD.

CONCLUSIONS

The results of the four MCO dialyzers evaluated in this study showed good efficiency, with no significant performance differences between them while being completely safe in terms of albumin loss. Likewise, the study confirms the superiority of HDx over high-flux HD with an efficacy close to that of post-dilution HDF.

Effects of high albumin leakage on survival between online hemodiafiltration and super high-flux hemodialysis: the HISTORY study

Background

All-cause mortality is lower with a high substitution volume in predilution (pre) and postdilution (post) online hemodiafiltration (OHDF) than with hemodialysis (HD), and mortality does not significantly differ between pre- and post-OHDF groups. Despite the improved survival with a high substitution volume, there may be limitations. On the other hand, either normoalbuminemia or high albumin leakage in HD can reduce mortality, and super high-flux (SHF) membrane dialyzers can reduce mortality compared with low-flux and high-flux membrane dialyzers. Here, we investigated the associations of serum albumin concentration (s-Alb), albumin leakage, and substitution volume with all-cause mortality in OHDF and SHF-HD.

Methods

In a 3-year retrospective observational study of patients receiving dialysis from April 1 to July 1, 2017, we developed a propensity score-matched model using 783 stable patients (SHF-HD, 355; OHDF, 428). We used the log-rank test to compare Kaplan–Meier survival curves and Cox regression analysis to calculate hazard ratio (HR). Cox regression analysis was also used to compare the effect of estimated albumin leakage (EAL) and substitution volume on 3-year all-cause mortality.

Results

All-cause mortality was significantly lower with high EAL than with low EAL (SHF-HD: P = 0.012, log-rank test; HR, 0.44; 95% confidence interval [CI] 0.23–0.85; OHDF: P = 0.027, log-rank test; HR, 0.41; 95% CI 0.18–0.93). The mortality of high EAL was not significantly different between high and low s-Alb in SHF-HD (3.5 ± 0.1 and 3.2 ± 0.2 g/dL) and OHDF (3.6 ± 0.2 and 3.2 ± 0.1 g/dL), despite significant differences in s-Alb. Mortality did not significantly differ between SHF-HD and OHDF with higher EAL ranges or a lower difference in EAL. Mortality in pre-OHDF was significantly correlated with EAL (P = 0.007, beta − 0.32) rather than substitution volume, and mortality in post-OHDF was not analyzed because of fewer deaths.

Conclusions

The results suggest that survival is improved more with high EAL than with low EAL in both OHDF and SHF-HD patients, that high EAL with mild-to-moderate hypoalbuminemia does not necessarily worsen survival in OHDF and SHF-HD patients, and that survival is equivalent between OHDF and SHF-HD patients with a similar level of EAL.

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.

Clustering of End Stage Renal Disease Patients by Dimensionality Reduction Algorithms According to Lymphocyte Senescence Markers

End stage renal disease (ESRD) engenders detrimental effects in the Immune system, manifested as quantitative alterations of lymphocyte subpopulations, akin, albeit not identical to those observed during the ageing process. We performed dimensionality reduction of an extended lymphocyte phenotype panel of senescent and exhaustion related markers in ESRD patients and controls with Principal Component Analysis (PCA) and Uniform Manifold Approximation and Projection (UMAP). The plane defined by the first two principal components of PCA showed two fuzzy clusters, for patients and controls, respectively, with loadings of non-senescent markers pointing towards the controls’ centroid. Naive lymphocytes were reduced in ESRD patients compared to controls (CD4+CD45RA+CCR7+ 200(150-328) vs. 426(260-585cells/μl respectively, P = 0.001, CD19+IgD+CD27- 54(26-85) vs. 130(83-262)cells/μl respectively, P < 0.001). PCA projections of the multidimensional ESRD immune phenotype suggested a more senescent phenotype in hemodialysis compared to hemodiafiltration treated patients. Lastly, clustering based on UMAP revealed three distinct patient groups, exhibiting gradual changes for naive, senescent, and exhausted lymphocyte markers. Machine learning algorithms can distinguish ESRD patients from controls, based on their immune-phenotypes and also, unveil distinct immunological groups within patients’ cohort, determined possibly by dialysis prescription.

Hemodiafiltration (HDF) versus expanded hemodialysis (HDx)

Medium cutoff (MCO) membranes have resulted in a novel dialyzer class designed to improve membrane permeability and have been postulated as an alternative to online hemodiafiltration since MCO membranes may achieve similar solute clearances. These membranes have been incorporated into clinical practice, and the term expanded HD (HDx) has been proposed to differentiate from high-flux hemodialysis. Efficacy, safety, and quality of life comparison of HDF versus HDx have been reviewed in this article.

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.

Effects of Japanese-style online hemodiafiltration on survival and cardiovascular events

Background

All-cause mortality can be reduced in patients receiving European-style high-volume post-dilution online hemodiafiltration (post-OHDF) compared with hemodialysis (HD). Japanese-style high-volume pre-dilution online hemodiafiltration (pre-OHDF) can also decrease all-cause mortality. No studies have investigated survival in patients receiving Japanese-style post-OHDF, and directly compared survival between pre-OHDF and post-OHDF. This study sought to clarify these issues.

Methods

We conducted this retrospective observational study at multiple facilities of our medical corporation, which have similar quality of healthcare management, from July 1, 2017 to July 1, 2020. Japanese-style OHDF included pre-OHDF and post-OHDF. Pre-OHDF and post-OHDF were each divided into high-volume and low-volume subgroups. We compared 3-year all-cause mortality and cardiovascular events between OHDF and high-flux HD using propensity score matching. In addition, we examined the effects of different modalities through comparisons between high-volume and low-volume pre-OHDF and between pre-OHDF and post-OHDF.

Results

Post-OHDF was associated with significantly lower all-cause mortality (P = 0.004, log-rank test; hazard ratio [HR] 0.257, 95% confidence interval [CI] 0.094–0.701) and cardiovascular events during all 3 years (P < 0.05) compared with HD. High-volume post-OHDF was associated with lower all-cause mortality compared with hemodialysis (log-rank test P = 0.022) but low-volume post-OHDF was not. Pre-OHDF was also associated with lower all-cause mortality (P < 0.001, log-rank test; HR 0.316; 95% CI 0.212–0.472) compared with HD but was not associated with cardiovascular events. All-cause mortality did not significantly differ between post-OHDF and pre-OHDF.

Conclusions

These findings suggest that Japanese-style post-OHDF may improve all-cause mortality to a level similar to that of pre-OHDF and that post-OHDF, particularly high-volume post-OHDF may reduce cardiovascular events.

Elucidating variations in outcomes among older end-stage renal disease patients on hemodialysis in Fukuoka Prefecture, Japan

Variations in health care outcomes and services potentially indicate resource allocation inefficiency. Therefore, this study was conducted to examine variations in mortality and hospitalization cases among end-stage renal disease (ESRD) patients receiving hemodialysis (HD) care from medical facilities located in 13 secondary medical care areas (SMAs) of Fukuoka prefecture, Japan. The research was designed as a retrospective, cross-sectional study using insurance claims data. The subjects of the study were older patients (over 65 years old) insured by the Fukuoka prefecture’s Latter-Stage Elderly Healthcare Insurance. Using an electronic claims database, we identified patients with chronic kidney disease (CKD) who had received HD care from April 1, 2017 to March 31, 2018. The CKD status was identified using International Classification of Disease, 10th revision code, and HD maintenance status was ascertained using specific insurance procedure codes. A total of 5,243 patients met our inclusion criteria and their records were subsequently reviewed. About 73% (n = 3,809) of patients had admission records during the period studied. Thus, the data regarding hospital length of stay (LOS) and admission costs were analyzed separately. Significant differences in terms of increased risks in hospitalization were evident in a number of SMAs. An increase in mortality risk due to heart failure and malignancy was observed in two separate SMAs. Also, analyzed LOS, total hospitalization cost, and cost per day according to SMAs showed statistically significant variations. The findings highlight the magnitude of the burden of CKD and ESRD in the community. The high prevalence of ESRD, associated mortality, and hospitalized HD patients signal the need for clinicians to assume broader roles in measures against chronic kidney disease through involvement in community awareness programs. To improve patient outcomes, improvement of regional health care provision, the level of medical care, and the development of existing human resources are needed.

Cardiovascular Risk Comparison between Expanded Hemodialysis Using Theranova and Online Hemodiafiltration (CARTOON): A Multicenter Randomized Controlled Trial

Expanded hemodialysis (HDx) with medium cutoff (MCO) membranes, which remove middle-to-large molecules well, may be a good option to replace online hemodiafiltration (online-HDF). To provide more evidence, this randomized controlled trial compared several cardiovascular parameters between patients undergoing HDx and online-HDF. Eighty patients undergoing thrice-weekly hemodialysis were randomly assigned to receive either HDx with a Theranova membrane (n = 43) or online-HDF (n = 37). The primary endpoints were changes in brachial-ankle pulse wave velocity (baPWV), echocardiographic parameters, and coronary artery calcium (CAC) scores over 1 year, and the secondary endpoints included blood cardiovascular biomarkers, mortality, and patient-reported outcomes. A linear mixed model and log-rank test were used to estimate the group differences. 65 patients had completed the trial. The changes in baPWV and echocardiographic parameters did not differ between the two groups. The CAC scores remained stable in the online-HDF group, whereas an increasing trend was shown in the HDx group (P = 0.012). Other endpoints, including cardiovascular and all-cause mortalities, were similar between the two groups. The changes in cardiovascular parameters did not differ between HDx with an MCO membrane and online-HDF. However, attention may be needed in patients with high CAC scores or scores with an increasing tendency when online-HDF is replaced with HDx with an MCO membrane.

Evaluation and comparison of polysulfone TS-UL and PMMA NF-U dialyzers versus expanded hemodialysis and postdilution hemodiafiltration

Toray has created a new generation of dialyzers, the polysulphone (TS) UL series, and polymethylmethacrylate (PMMA) NF-U series, which offer enhanced efficacy over the previous TS-S series and NF-H series. The aim of this study was to evaluate the safety and efficacy of these dialyzer series versus contrasted expanded hemodialysis (HDx) and postdilution hemodiafiltration (HDF). We conducted a prospective study in 12 patients. Each patient underwent six dialysis sessions: FX80 Cordiax in HD, Toraysulfone TS-1.8 UL in HD, Theranova 400 in HDx, polymethylmethacrylate (PMMA) NF-2.1 U in HDF, Toraysulfone TS-2.1 UL in HDF, and FX80 Cordiax in HDF. The removal ratios (RRs) of urea, creatinine, ß₂ -microglobulin, myoglobin, prolactin, α₁ -microglobulin, α₁ -acid glycoprotein, and albumin were compared intraindividually. Dialysate albumin loss was also measured. The RRs for β₂ -microglobulin, myoglobin, prolactin, α₁ -microglobulin, and α₁ -acid glycoprotein were higher with the TS-2.1 UL and FX80 Cordiax dialyzers in HDF than those obtained with HD treatments and NF-2.1 U in HDF. The β₂ -microglobulin, myoglobin, and prolactin RRs were also higher with HDx than those obtained with HD treatments. The myoglobin and prolactin RRs were higher with TS-1.8 UL in HD than those obtained with helixone dialyzers in HD. Dialysate albumin loss was less than 3 g in all situations except in TS-2.1 UL in HDF. The highest global removal score values were obtained with the TS-2.1 UL and helixone dialyzers in HDF. Significant differences were found between all study situations. In conclusion, the new generation dialyzers, Toraysulfone TS Series UL and PMMA NF-U series, show excellent behaviour and tolerance in HD and HDF, representing an upgrade versus their predecessor series. The higher permeability of the TS UL series has been proven with higher efficiency in HD and maximum performance in HDF. The new PMMA NF-U series allows the use of HDF with good efficiency and complete safety.

Efficacy and safety of the Clearum dialyzer

The Clearum dialyzer, built by Medtronic, became commercially available in several European countries in 2020, but there are still no reports of in vivo data. The aim of this study was to evaluate the efficacy and risk of hypoalbuminemia of this dialyzer compared with previously evaluated hemodialysis (HD), expanded hemodialysis (HDx), and postdilution hemodiafiltration (HDF) treatments. A prospective study was carried out in 15 patients. Each patient underwent seven dialysis sessions: FX80 Cordiax in HD, Clearum HS17 in HD, Phylther 17-SD in HDx, Theranova 400 in HDx, Phylther 17-G in postdilution HDF, Clearum HS17 in postdilution HDF, and FX80 Cordiax in postdilution HDF. The reduction ratios of urea, creatinine, ß₂ -microglobulin, myoglobin, prolactin, α₁ -microglobulin, α₁ -acid glycoprotein, and albumin were compared intraindividually. Dialysate albumin loss was also measured. Comparison of dialysis techniques revealed no differences between small molecules, but HDx and HDF were significantly higher than HD with medium and large molecular weights. The Clearum dialyzer in HDF obtained similar results to FX80 Cordiax in HDF, was slightly superior to Phylther 17-G in HDF, and was statistically superior to both dialyzers in HDx. Albumin losses with the Clearum dialyzer were among the lowest, both in HD and HDF treatments. The highest global removal score (GRS) values were obtained with the helixone and Clearum dialyzers in HDF, with similar results both in HD and HDF. In addition, the GRS values with HDx treatments were statistically significantly higher than those with HD. The new Clearum dialyzer has excellent behavior and tolerance in HD and HDF. Its adequate permeability has been proven with its maximal performance in HDF, which could represent an upgrade versus its predecessor polyphenylene dialyzers.

Medium Cut-Off Dialysis Membrane and Dietary Fiber Effects on Inflammation and Protein-Bound Uremic Toxins: A Systematic Review and Protocol for an Interventional Study

The aim of this systematic review is to investigate the effects of the use of a medium cut-off membrane (MCO) and dietary fiber on the concentration of protein-bound uremic toxins (PBUTs) and inflammatory markers in hemodialysis (HD) patients. Of 11,397 papers originally found, eight met the criteria of randomized controlled trial design. No study examined the effects of MCO membranes on PBUTs. Three studies examined the reduction in inflammatory markers with MCO membranes compared to high-flux HD membranes and showed no significant differences. Five studies of dietary fiber supplementation showed an inconclusive positive effect on PBUT levels and a significant positive effect on the reduction in inflammatory markers (interleukin-6 reduction: standardized difference in means −1.18; 95% confidence interval −1.45 to −0.9 for dietary fiber supplementation vs. control; p < 0.001). To date, no study has combined the use of an MCO membrane and fiber supplementation to reduce PBUT levels and inflammation with online hemodiafiltration as a comparator. A rationale and protocol for an interventional trial using a combination of MCO membrane dialysis and fiber supplementation to lower inflammatory markers and PBUT concentrations are presented.

Stepwise achievement of high convection volume in post-dilution hemodiafiltration: A prospective observational study

High-volume online hemodiafiltration (HDF) has been reported to reduce the patient's mortality. However, achieving a high convection volume is challenging. In this prospective study, we investigated the feasibility of achieving high-volume HDF with ≥21 L substitution volume via modification of blood flow rate (BFR), needle size, and dialysis membrane. In 30 patients undergoing hemodialysis, we followed a stepwise protocol and gradually increased the BFR (280→300→330 ml/min; steps 1, 2, and 3) and needle size (16→15 G; step 4). After changing dialyzer surface area (1.8 m² →2.5 m² ), the BFR and needle size were similarly increased stepwise (steps 5, 6, 7, and 8). The mean substitution volume was 18.7 ± 2.2 L at step 1 and it significantly increased to 25.1 ± 2.6 L by step 8. A substitution volume of 21 L was achieved by 13.3% of patients in step 1 and by 96.7% after step 8. The substitution volume was higher for the dialyzer with a large surface area and for the larger needle (15 G). Between steps 1 and 8, the Kt/V and β₂ microglobulin reduction ratios also improved significantly. High-volume HDF is feasible through a stepwise increase in the BFR, needle size, and surface area of the dialysis membrane.

The probability of receiving a kidney transplantation in end-stage kidney disease patients who are treated with haemodiafiltration or haemodialysis: a pooled individual participant data from four randomised controlled trials

Background

Due to a critical shortage of available kidney grafts, most patients with Stage 5 Chronic Kidney Disease (CKD5) require bridging dialysis support. It remains unclear whether treatment by different dialysis modalities changes the selection and/or preparation of a potential transplant candidate. Therefore, we assessed whether the likelihood of receiving kidney transplant (both living or deceased kidney donors) differs between haemodialysis (HD) and online haemodiafiltration (HDF) in patients with CKD5D.

Methods

Individual participant data from four randomised controlled trials comparing online HDF with HD were used. Information on kidney transplant was obtained during follow-up. The likelihood of receiving a kidney transplant was compared between HD and HDF, and evaluated across different subgroups: age, sex, diabetes, history of cardiovascular disease, albumin, dialysis vintage, fistula, and level of convection volume standardized to body surface area. Hazard ratios (HRs), with corresponding 95% confidence intervals (95% CI), comparing the effect of online HDF versus HD on the likelihood of receiving a kidney transplant, were estimated using Cox proportional hazards models with a random effect for study.

Results

After a median follow-up of 2.5 years (Q1 to Q3: 1.9–3.0), 331 of the 1620 (20.4%) patients with CKD5D received a kidney transplant. This concerned 22% (n = 179) of patients who were treated with online HDF compared with 19% (n = 152) of patients who were treated with HD. No differences in the likelihood of undergoing a kidney transplant were found between the two dialysis modalities in both the crude analyse (HR: 1.07, 95% CI: 0.86–1.33) and adjusted analysis for age, sex, diabetes, cardiovascular history, albumin, and creatinine (HR: 1.15, 95%-CI: 0.92–1.44). There was no evidence for a differential effect across subgroups based on patient- and disease-characteristics nor in different categories of convection volumes.

Conclusions

Treatment with HD and HDF does not affect the selection and/or preparation of CKD5D patients for kidney transplant given that the likelihood of receiving a kidney transplant does not differ between the dialysis modalities. These finding persisted across a variety of subgroups differing in patient and disease characteristics and is not affected by the level of convection volume delivered during HDF treatment sessions.

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

BACKGROUND AND OBJECTIVES

High-volume online hemodiafiltration (OL-HDF) associates with improved outcomes compared to hemodialysis (HD), provided adequate dosing is achieved as estimated from convective volume (CV). Achievement of high CV and its impact on biochemical indicators following a standardized protocol converting HD patients to OL-HDF has not been systematically reported. We assessed the success of implementation of OL-HDF in clinics naïve to the modality.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

We analyzed the results of the implementation of postdilution OL-HDF in patients randomized to the HDF arm of a clinical trial (impact of hemoDiaFIlTration on physical activity and self-reported outcomes: a randomized controlled trial (HDFit) trial [ClinicalTrials.gov:NCT02787161]). The day before randomization of the first patient to OL-HDF at each clinic staff started a 3-day in-person training module on operation of Fresenius 5008 CorDiax machine in HDF mode. Patients were converted from high-flux HD to OL-HDF under oversight of trainers. OL-HDF was performed over a 6-months follow-up with a CV target of 22 L/treatment. We characterized median achieved CV >22 L/treatment record and analyzed the impact of HDF on biochemical variables.

RESULTS

Ninety-seven patients (mean age 53 ± 16 years, 29% with diabetes, and 11% had a catheter) from 13 clinics randomized to the OL-HDF arm of the trial were converted from HD to HDF. Median CV > 22 L/treatment was achieved in 99% (94/95) of OL-HDF patients throughout follow-up. Monthly mean CV ranged from 27.1 L to 27.5 L. OL-HDF provided an increased single pool Kt/V at 3-months (0.2 [95% CI: 0.1-0.3]) and 6-months (0.2 [95% CI: 0.1-0.4]) compared to baseline, and reduced phosphate at 3-months (-0.4 mg/dL [95% CI: -0.8 to -0.12]) of follow-up.

CONCLUSIONS

High-volume online hemodiafiltration was successfully implemented with 99% of patients achieving protocol defined CV target. Monthly mean CV was consistently >22 L/treatment during follow-up. Kt/V increased, and phosphate decreased with OL-HDF. Findings resulting from a short training period in several dialysis facilities appear to suggest HDF is an easily implementable technique.

Benefits and harms of high-dose haemodiafiltration versus high-flux haemodialysis: the comparison of high-dose haemodiafiltration with high-flux haemodialysis (CONVINCE) trial protocol

INTRODUCTION

End-stage kidney disease (ESKD) is a major public health problem affecting more than 2 million people worldwide. It is one of the most severe chronic non-communicable diseases. Haemodialysis (HD) is the most common therapeutic option but is also associated with a risk of cardiovascular events, hospitalisation and suboptimal quality of life. Over the past decades, haemodiafiltration (HDF) has become available. Although high-dose HDF has shown some promising survival advantage compared to conventional HD, the evidence remains controversial. A Cochrane systematic review found, in low-quality trials, with various convective forms of dialysis, a reduction in cardiovascular, but not all-cause mortality and the effects on non-fatal cardiovascular events and hospitalisation were uncertain. In contrast, an individual patient data analysis suggested that high-dose HDF reduced both all-cause and cardiovascular mortality compared to HD. In view of these discrepant results, a definitive trial is required to determine whether high-dose HDF is preferable to high-flux HD. The comparison of high-dose HDF with high-flux HD (CONVINCE) study will assess the benefits and harms of high-dose HDF versus a conventional high-flux HD in adults with ESKD.

METHODS AND ANALYSIS

This international, prospective, open label, randomised controlled trial aims to recruit 1800 ESKD adults treated with HD in nine European countries. Patients will be randomised 1:1 to high-dose HDF versus continuation of conventional high-flux HD. The primary outcome will be all-cause mortality at 3 years' follow-up. Secondary outcomes will include cause-specific mortality, cardiovascular events, all-cause and infection-related hospitalisations, patient-reported outcomes (eg, health-related quality of life) and cost-effectiveness.

ETHICS AND DISSEMINATION

The CONVINCE study will address the question of benefits and harms of high-dose HDF compared to high-flux HD for kidney replacement therapy in patients with ESKD with a focus on survival, patient perspectives and cost-effectiveness.

TRIAL REGISTRATION NUMBER

Netherlands National Trial Register (NTR 7138).

Immune response to influenza vaccination in ESRD patients undergoing hemodialysis vs. hemodiafiltration

BACKGROUND

On-line hemodiafiltration (HDF) clears more azotemic toxins compared to high-flux hemodialysis (HD). The response to vaccination is impaired in dialysis patients. We wished to determine whether the immune responses to influenza vaccine in dialysis patients treated by HDF were stronger than those treated by HD.

MATERIALS AND METHODS

We conducted a prospective cohort study in chronic dialysis patients during the 2016 and 2017 influenza seasons. All participants received a single standard dose of trivalent influenza vaccine, and we studied the elicited humoral immune response by hemagglutination inhibition test, and cell-mediated immune response by enumeration of lymphocyte cellular markers and proliferation assays.

RESULTS

We immunized 60 end-stage renal disease (ESRD) patients: 42 (70%) treated with HD and 18 patients (30%) with HDF. The median (interquartile range) age was 65.0 (55.0-74.5) years. All patients developed seroprotection to at least one influenza vaccine strain at one month post-vaccination, and did not differ between groups. By logistic regression, age was the only factor independently associated with seroconversion to all vaccine strains (odds ratio 0.89, 95% confidence interval 0.80-0.98; p = 0.022). Seroprotection to all vaccine strains was sustained for longer in patients treated with HDF, and the results remained the same after age adjustment. For cellular immune response, patients who seroconverted to all vaccine strains had higher CD38+ T cell subpopulations pre-vaccination. Patients treated by HDF had higher lymphocyte proliferation to circulating influenza A strains.

CONCLUSIONS

Seroconversion to all influenza vaccine strains was associated with age. Patients treated with HDF demonstrated seroprotection was sustained for longer compared to those treated by HD and greater lymphocyte proliferation to circulating influenza A strains. These encouraging results for HDF require confirmation in a larger dialysis population.

TRIAL REGISTRATION

ClinicalTrial.gov, NCT04122222.

Improved Outcomes in Hemodialysis/Hemodiafiltration Treatments Applying Exercise and Physiological Monitoring Techniques: Preliminary Results

End-stage renal disease affects millions of people worldwide, and the only definitive solutions are renal transplants that are not widely available. Temporary solutions are renal replacement therapies such as peritoneal dialysis, hemodialysis and hemodiafiltration. These therapies as they are applied today are just partial measures and have many drawbacks and complications such as high mortality rates and high costs due to the use of supplemental drugs and emergency room visits. Many enhancements to the therapies have been published, but they are not applied consistently in real world practice. Our work presents the results from the systematic application of several techniques to provide individualized therapies that can minimize the drawbacks and improve patient outcomes. This approach is based on the use of exercise, analysis of cardiovascular parameters, such as heart-rate variability, body composition and dry weight measurements through the use of bioimpedance and real-time monitoring of energy expenditure and nutrition intradialytically in order to provide individualized and dynamically variable therapies. Results show that patients can lead long, productive lives while maintaining a quality of life equivalent to that of a renal transplant.

Clinical evidence on haemodiafiltration

Haemodiafiltration (HDF) combines diffusive and convective solute removal in a single treatment session. HDF provides a greater removal of higher molecular weight uraemic retention solutes than conventional high-flux haemodialysis (HD). Recently completed randomized clinical trials suggest better patient survival with online HDF. The treatment is mainly used in Europe and Japan. This review gives a brief overview of the presently available evidence of the effects of HDF on clinical end points, it speculates on possible mechanisms of a beneficial effect of HDF as compared with standard HD and ends with some perspectives for the future.

Albumin handling in different hemodialysis modalities

Hypoalbuminemia is a major risk factor for morbidity and mortality in dialysis patients. With increasing interest in highly permeable membranes and convective therapies to improve removal of middle molecules, transmembrane albumin loss increases accordingly. Currently, the acceptable upper limit of albumin loss for extracorporeal renal replacement therapies is unknown. In theory, any additional albumin loss should be minimized because it may contribute to hypoalbuminemia and adversely affect the patient's prognosis. However, hypoalbuminemia-associated mortality may be a consequence of inflammation and malnutrition, rather than low albumin levels per se. The purpose of this review is to give an overview of albumin handling with different extracorporeal renal replacement strategies. We conclude that the acceptable upper limit of dialysis-related albumin loss remains unknown. Whether enhanced middle molecule removal outweighs the potential adverse effects of increased albumin loss with novel highly permeable membranes and convective therapies is yet to be determined.

Online hemodiafiltration and mortality risk in end-stage renal disease patients: A critical appraisal of current evidence

The life expectancy of end-stage renal disease patients undergoing regular hemodialysis (HD) remains significantly lower than in the general population. Reducing excess mortality by improving renal replacement options is an unmet medical need. Online post-dilution hemodiafiltration (HDF) has been promoted as the gold standard, offering improved clinical outcomes, based on numerous observational studies that suggest a reduced mortality risk and lower morbidity with HDF compared with standard HD. However, most randomized controlled trials (RCTs) have failed to demonstrate a significant beneficial effect of HDF on all-cause mortality. The effects on secondary outcomes were often negligible or absent. Unfortunately, these RCTs were characterized by a moderate to high risk of bias. In post-hoc analyses of the largest RCTs and meta-analysis of individual participant data from four RCTs, HDF patients receiving the highest convection volume consistently and dose-dependently saw superior outcomes. However, as these studies were not designed a priori to clarify this issue, and there are no indisputable mechanisms underlying reduced mortality risks, we cannot exclude the possibility that the health status of patients (with vascular access as a proxy) may affect outcomes more than the convective technique itself. There is currently insufficient evidence to support the contention that high-volume HDF confers relevant benefits to patients over standard HD. The conflicting data of published RCTs reduce confidence in the superiority of high-volume convective therapy. Hopefully, ongoing large RCTs (for example, CONVINCE) may supply an indisputable answer to the crucial question of high-volume HDF.

High-permeability alternatives to current dialyzers performing both high-flux hemodialysis and postdilution online hemodiafiltration

Most high-flux dialyzers can be used in both hemodialysis (HD) and online hemodiafiltration (OL-HDF). However, some of these dialyzers have higher permeability and should not be prescribed for OL-HDF to avoid high albumin losses. The aim of this study was to compare the safety and efficacy of a currently used dialyzer in HD and OL-HDF with those of several other high permeability dialyzers which should only be used in HD. A prospective, single-center study was carried out in 21 patients. Each patient underwent 5 dialysis sessions with routine dialysis parameters: 2 sessions with Helixone (HD and postdilution OL-HDF) and 1 session each with steam sterilized polyphenylene, polymethylmethacrylate (PMMA), and medium cut-off (MCO) dialyzers in HD treatment. The removal ratios (RR) of urea, creatinine, ß₂ -microglobulin, myoglobin, prolactin, α₁ -microglobulin, α₁ -acid glycoprotein, and albumin were compared intraindividually. A proportional part of the dialysate was collected to quantify the loss of various solutes, including albumin. Urea and creatinine RRs with the Helixone-HDF and MCO dialyzers were higher than with the other 3 dialyzers in HD. The β₂ -microglobulin, myoglobin and prolactin RRs with Helixone-HDF treatment were significantly higher than those obtained with all 4 dialyzers in HD treatment. The β₂ -microglobulin value obtained with the MCO dialyzer was also higher than that obtained with the other 3 dialyzers in HD treatment. The myoglobin RR with MCO was higher than those obtained with Helixone and PMMA in HD treatment. The prolactin RR with Helixone-HD was significantly lower than those obtained in the other 4 study sessions. The α₁ -microglobulin and α₁ - acid glycoprotein RRs with Helixone-HDF were significantly higher than those obtained with Helixone and PMMA in HD treatment. The albumin loss varied from 0.54 g with Helixone-HD to 3.3 g with polyphenylene. The global removal score values ((Urea_RR + β₂ -microglobulin_RR + myoglobin_RR + prolactin_RR + α₁ -microglobulin_RR + α₁ -acid glycoprotein_RR - albumin_RR )/6) were 43.7% with Helixone-HD, 47.7% with PMMA, 54% with polyphenylene, 54.8% with MCO and 59.6% with Helixone-HDF, with significant differences. In conclusion, this study confirms the superiority of OL-HDF over HD with the high-flux dialyzers that allow both treatments. Although new dialyzers with high permeability can only be used in HD, they are in an intermediate position and some are very close to OL-HDF.

Effects of high-volume online mixed-hemodiafiltration on anemia management in dialysis patients

Background

Anemia is a major comorbidity of patients with end-stage renal disease and poses an enormous economic burden to health-care systems. High dose erythropoiesis-stimulating agents (ESAs) have been associated with unfavorable clinical outcomes. We explored whether mixed-dilution hemodiafiltration (Mixed-HDF), based on its innovative substitution modality, may improve anemia outcomes compared to the traditional post-dilution hemodiafiltration (Post-HDF).

Methods

We included 174 adult prevalent dialysis patients (87 on Mixed-HDF, 87 on Post-HDF) treated in 24 NephroCare dialysis centers between January 2010 and August 2016 into this retrospective cohort study. All patients were dialyzed three times per week and had fistula/graft as vascular access. Patients were matched at baseline and followed over a one-year period. The courses of hemoglobin levels (Hb) and monthly ESA consumption were compared between the two groups with linear mixed models.

Results

Mean baseline Hb was 11.9±1.3 and 11.8±1.1g/dl in patients on Mixed- and Post-HDF, respectively. While Hb remained stable in patients on Mixed-HDF, it decreased slightly in patients on Post-HDF (at month 12: 11.8±1.2 vs 11.1±1.2g/dl). This tendency was confirmed by our linear mixed model (p = 0.0514 for treatment x time interaction). Baseline median ESA consumption was 6000 [Q1:0;Q3:16000] IU/4 weeks in both groups. Throughout the observation period ESA doses tended to be lower in the Mixed-HDF group (4000 [Q1:0;Q3:16000] vs 8000 [Q1:0;Q3:20000] IU/4 weeks at month 12; p = 0.0791 for treatment x time interaction). Sensitivity analyses, adjusting for differences not covered by matching at baseline, strengthened our results (Hb: p = 0.0124; ESA: p = 0.0687).

Conclusions

Results of our explorative study suggest that patients on Mixed-HDF may have clinical benefits in terms of anemia management. This may also have a beneficial economic impact. Future studies are needed to confirm our hypothesis-generating results and to provide additional evidence on the potential beneficial effects of Mixed-HDF.

Outcomes and practice patterns with hemodiafiltration in Shanghai: a longitudinal cohort study

BACKGROUND

Globally, there is increased clinical interest and uptake of hemodiafiltration (HDF) for increased removal of uremic toxins. To date, there has been no epidemiological analysis of HDF in China. We present HDF practice patterns and associated mortality risk in Shanghai.

METHODS

This is an observational, prospectively collected, retrospective analysis of 9351 Chinese patients initiating hemodialysis in Shanghai from 2007 to 2014. The primary exposure was hemodialysis sub-modality at inception, classified into hemodiafiltration (HDF) and hemodialysis (HD), with adjustment for concommitant hemoperfusion. The primary outcome was patient mortality. We used Cox proportional hazards regression and Fine and Gray's proportional subhazards regression, with multiple imputation of missing co-variates by the chained equation method, adjusting for demographic and clinical variables.

RESULTS

Overall, patients in the cohort were younger, with a more males, and with a lower body mass index when compared to corresponding non-Asian cohorts. Mortality rate was low although it doubled over the period of observation. HDF utilization increased from 7% of patients in 2007 to 42% of patients in 2014. The majority of patients received HDF once a week. The adjusted hazard ratio of death (95% confidence intervals) for HDF versus HD was 0.85 (0.71-1.03), and corresponding sub-hazard ratio 0.86 (0.71-1.03). There was strong effect modification by age. In those aged 40-60 years, the hazard ratio (95% confidence intervals) was 0.65 (0.45-0.94), and sub-hazard ratio also 0.65 (0.45-0.95).

CONCLUSIONS

Our study has certain limitations resulting from the limited number of co-variates available for modelling, missing data for some co-variates, and the lack of verification of data against source documentation. Notwithstanding, there is evidence of clinical benefit from HDF in China, and potential to improve patient outcomes through the greater removal of middle and larger uremic solutes.

High convective volumes are associated with improvement in metabolic profile in diabetic patients on online haemodiafiltration

BACKGROUND AND OBJECTIVE

Online haemodiafiltration (OL-HDF) with high convective transport volumes improves patient survival in haemodialysis. Limiting the amount of convective volume has been proposed in patients with diabetes mellitus due to glucose load that is administered with replacement fluid. The objective of the study was to analyse the influence of substitution volume on the evolution of the metabolic profile and body composition of incident diabetic patients on OL-HDF.

MATERIAL AND METHODS

Prospective observational study in 29 incident diabetic patients on postdilution OL-HDF. Baseline data included clinical and demographic data, laboratory parameters (metabolic, nutritional and inflammatory profile) and body composition with bioimpedance spectroscopy (BIS). Laboratory parameters and mean substitution volume per session were collected every 4 months, and in 23 patients a further BIS was performed after a minimum of one year. Variations in glycosylated haemoglobin (HbA1c), triglycerides, total cholesterol, LDL-c, HDL-c, albumin, prealbumin and C reactive protein (CRP) were calculated at one year, 2 years, 3 years, and at the end of follow-up. Quarterly and annual variations were calculated as independent periods, and changes in body composition were analysed.

RESULTS

Age at baseline was 69.7±13.6 years, 62.1% were male, 72.3±13.9kg, 1.78±0.16m², with 48 (35.5-76) months on dialysis. Approximately 81.5% received insulin, 7.4% antidiabetic drugs and 51.9% statins. Mean substitution volume was 26.9±2.9L/session and follow-up period (time on OL-HDF) was 40.4±26 months. A significant correlation was observed between mean substitution volume and the increase in HDL-c (r=0.385, p=0.039) and prealbumin levels (r=0.404, p=0.003) throughout follow-up. Moreover, substitution volume was correlated with a reduction in CRP levels at one year (r=-0.531, p=0.005), 2 years (r=-0.463, p=0.046), and at the end of follow-up (r=-0.498, p=0.007). Patients with mean substitution volume >26.9L/session had a higher reduction in triglycerides and CRP, and an increase in HDL-c levels. These patients with >26.9L/session finished the study with higher HDL-c (48.1±9.4mg/dL vs. 41.2±11.6mg/dL, p=0.025) and lower CRP levels (0.21 [0.1-2.22] mg/dL vs. 1.01 [0.15-6.96] mg/dL, p=0.001), with no differences at baseline. Quarterly comparisons between substitution volume and laboratory changes [n=271] showed a significant correlation with a reduction in HbA1c (r=-0.146, p=0.021). Similar findings were obtained with annual comparisons [n=72] (r=-0.237, p=0.045). An annual mean substitution volume over 26.6L/session (29.3±1.7L/session vs. 23.9±1.9L/session) was associated with a reduction in HbA1c (-0.51±1.24% vs. 0.01±0.88%, p=0.043). No correlation was observed between substitution volume and changes in weight, body mass index or BIS parameters.

CONCLUSION

There is not enough evidence to restrict convective transport in diabetic patients on OL-HDF due to the glucose content of the replacement fluid.

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.

Hemodynamic Instability during Dialysis: The Potential Role of Intradialytic Exercise

Acute haemodynamic instability is a natural consequence of disordered cardiovascular physiology during haemodialysis (HD). Prevalence of intradialytic hypotension (IDH) can be as high as 20–30%, contributing to subclinical, transient myocardial ischemia. In the long term, this results in progressive, maladaptive cardiac remodeling and impairment of left ventricular function. This is thought to be a major contributor to increased cardiovascular mortality in end stage renal disease (ESRD). Medical strategies to acutely attenuate haemodynamic instability during HD are suboptimal. Whilst a programme of intradialytic exercise training appears to facilitate numerous chronic adaptations, little is known of the acute physiological response to this type of exercise. In particular, the potential for intradialytic exercise to acutely stabilise cardiovascular hemodynamics, thus preventing IDH and myocardial ischemia, has not been explored. This narrative review aims to summarise the characteristics and causes of acute haemodynamic instability during HD, with an overview of current medical therapies to treat IDH. Moreover, we discuss the acute physiological response to intradialytic exercise with a view to determining the potential for this nonmedical intervention to stabilise cardiovascular haemodynamics during HD, improve coronary perfusion, and reduce cardiovascular morbidity and mortality in ESRD.

Differential hemoglobin A sequestration between hemodialysis modalities

This report evaluates plasma protein patterns, dialysates and protein analysis of used dialysis membranes from the same patient under hemodialysis in three separate modalities, using high-flux membranes in concentration-driven transport (HD), convection-driven hemofiltration (HF) and combined hemodialfiltration (HDF). The plasma protein changes induced by each of the three dialysis modalities showed small differences in proteins identified towards our previous plasma analyses of chronic kidney disease (CKD) patients. The used dialysate peptide concentrations likewise exhibited small differences among the modalities and varied in the same relative order as the plasma changes, with protein losses in the order HD>HDF>HF. The membrane protein deposits allowed quantification of the relative Hb removal ratios as ~1.7 for HD and ~1.2 for HDF vs. ~1.0 for HF. Hence, plasma protein alterations, dialysate peptide contents and membrane Hb deposits all identify HD as the modality with the most extensive filtration results and exemplifies the accessibility of protein analysis of used membrane filters for evaluation of dialysis efficiencies.

Evaluation of the dialyser inner diameter in online haemodiafiltration

INTRODUCTION

Online haemodiafiltration (OL-HDF) has been associated with increased survival. To date, the influence of the inner diameter of the hollow fibres of the dialyser on convective volume has not been well established. The objective of the study was to evaluate the effect of increasing the inner diameter of the dialyser on the convective volume and removal capacity.

MATERIAL AND METHODS

We included 16 patients in posdilutional OL-HDF with autosubstitution. Each patient was analysed in 4 sessions in which the inner diameter varied; 185μm (FX60 Cordiax and FX80 Cordiax) versus 210μm (FX600 Cordiax and FX800 Cordiax). Different solutes were measured at the beginning and end of each dialysis session.

RESULTS

No differences in the convective volume were found with an increased inner diameter: 32.3±3.1 vs. 31.8±3.6 l/session (FX60 vs. FX600) and 33.7±4.3 vs. 33.5±3.8 l/session (FX80 vs. FX800). The reduction percentages also did not differ: urea 83.7±4.5 vs. 84.1±3.4 for FX60 and FX600, and 82.7±4.1 vs. 83.6±3.8 for FX80 vs. FX800; creatinine similar 78.2±5.6 vs. 77.8±4.6 y 77.1±5.4 vs. 78.1±4.9; β₂-microglobulin 82.2±4.3 vs. 82.9±4.2, and 82.9±4.7 vs. 84.0±3.8; myoglobin 71.0±10 vs. 70.2±9 and 72.8±11 vs. 75.0±10; prolactin 70.4±9 vs. 68.1±9, and 72.2±10 vs. 73.4±8.2; and α₁-microglobulin 22.9±10 vs. 21.6±10, and 26.5±12 vs. 28.8±11, respectively.

CONCLUSION

The increase in the inner diameter of the hollow fibres did not result in improved convective volume and removal capacity.

A new generation of cellulose triacetate suitable for online haemodiafiltration

BACKGROUND

Online haemodiafiltration (OL-HDF) is currently the most effective dialysis technique that also improves survival. To date, high permeability membranes with low albumin loss, such as polysulfone, polyamide and polyacrylonitrile membranes have been the most widely used. However, the initially restricted use of cellulose triacetate (CTA) membranes in OL-HDF has expanded. The aim of the study was to ascertain whether the latest generation asymmetric CTA membranes are more effective in obtaining high convective transport.

PATIENTS AND METHODS

A total of 16 patients (10 males and 6 females) undergoing OL-HDF were studied. Each patient underwent 4 different sessions, with haemodialysis or OL-HDF, and/or with CTA or asymmetric CTA 1.9 m² membranes. Each session was assigned in a randomised order. Serum levels of urea, creatinine, β₂-microglobulin, myoglobin, prolactin, α₁-microglobulin, α₁-acid glycoprotein and albumin where measured at the beginning and end of each session to obtain the reduction rate. The loss of solutes and albumin was quantified from the dialysate.

RESULTS

A significantly greater replacement volume in OL-HDF (32.1±3.1 vs. 19.7±4.5 l, P<.001) was obtained by using asymmetrical CTA membranes compared to conventional CTA membranes. Regarding uraemic toxin removal, both membranes obtained similar results for small molecules, whereas asymmetric CTA membranes achieved better results for large molecules, increasing the reduction ratio by 29% for β₂-microglobulin, 27.7% for myoglobin, 19.5% for prolactin, 49% for α₁-microglobulin and double for α₁-acid glycoprotein (P<0.001 in all situations). The loss of albumin was less than 2g for all treatment sessions.

CONCLUSION

Latest-generation asymmetric CTA have proven to be effective in attaining OL-HDF objectives without increased albumin loss.

Phosphate Kinetic Models in Hemodialysis: A Systematic Review

BACKGROUND

Understanding phosphate kinetics in dialysis patients is important for the prevention of hyperphosphatemia and related complications. One approach to gain new insights into phosphate behavior is physiologic modeling. Various models that describe and quantify intra- and/or interdialytic phosphate kinetics have been proposed, but there is a dearth of comprehensive comparisons of the available models. The objective of this analysis was to provide a systematic review of existing published models of phosphate metabolism in the setting of maintenance hemodialysis therapy.

STUDY DESIGN

Systematic review.

SETTING & POPULATION

Hemodialysis patients.

SELECTION CRITERIA FOR STUDIES

Studies published in peer-reviewed journals in English about phosphate kinetic modeling in the setting of hemodialysis therapy.

PREDICTOR

Modeling equations from specific reviewed studies.

OUTCOMES

Changes in plasma phosphate or serum phosphate concentrations.

RESULTS

Of 1,964 nonduplicate studies evaluated, 11 were included, comprising 9 different phosphate models with 1-, 2-, 3-, or 4-compartment assumptions. Between 2 and 11 model parameters were included in the models studied. Quality scores of the studies using the Newcastle-Ottawa Scale ranged from 2 to 11 (scale, 0-14). 2 studies were considered low quality, 6 were considered medium quality, and 3 were considered high quality.

LIMITATIONS

Only English-language studies were included.

CONCLUSIONS

Many parameters known to influence phosphate balance are not included in existing phosphate models that do not fully reflect the physiology of phosphate metabolism in the setting of hemodialysis. Moreover, models have not been sufficiently validated for their use as a tool to simulate phosphate kinetics in hemodialysis therapy.

The importance of considering competing treatment affecting prognosis in the evaluation of therapy in trials: the example of renal transplantation in hemodialysis trials

Background

During the follow-up in a randomized controlled trial (RCT), participants may receive additional (non-randomly allocated) treatment that affects the outcome. Typically such additional treatment is not taken into account in evaluation of the results. Two pivotal trials of the effects of hemodiafiltration (HDF) versus hemodialysis (HD) on mortality in patients with end-stage renal disease reported differing results. We set out to evaluate to what extent methods to take other treatments (i.e. renal transplantation) into account may explain the difference in findings between RCTs. This is illustrated using a clinical example of two RCTs estimating the effect of HDF versus HD on mortality.

Methods

Using individual patient data from the Estudio de Supervivencia de Hemodiafiltración On-Line (ESHOL; n  =  902) and The Dutch CONvective TRAnsport STudy (CONTRAST; n  = 714) trials, five methods for estimating the effect of HDF versus HD on all-cause mortality were compared: intention-to-treat (ITT) analysis (i.e. not taking renal transplantation into account), per protocol exclusion (PP excl ; exclusion of patients who receive transplantation), PP cens (censoring patients at the time of transplantation), transplantation-adjusted (TA) analysis and an extension of the TA analysis (TA ext ) with additional adjustment for variables related to both the risk of receiving a transplant and the risk of an outcome (transplantation-outcome confounders). Cox proportional hazards models were applied.

Results

Unadjusted ITT analysis of all-cause mortality led to differing results between CONTRAST and ESHOL: hazard ratio (HR) 0.95 (95% CI 0.75-1.20) and HR 0.76 (95% CI 0.59-0.97), respectively; difference between 5 and 24% risk reductions. Similar differences between the two trials were observed for the other unadjusted analytical methods (PP cens, PP excl , TA) The HRs of HDF versus HD treatment became more similar after adding transplantation as a time-varying covariate and including transplantation-outcome confounders: HR 0.89 (95% CI 0.69-1.13) in CONTRAST and HR 0.80 (95% CI 0.62-1.02) in ESHOL.

Conclusions

The apparent differences in estimated treatment effects between two dialysis trials were to a large extent attributable to differences in applied methodology for taking renal transplantation into account in their final analyses. Our results exemplify the necessity of careful consideration of the treatment effect of interest when estimating the therapeutic effect in RCTs in which participants may receive additional treatments.

Hemodiafiltration Reduces All-Cause and Cardiovascular Mortality in Incident Hemodialysis Patients: A Propensity-Matched Cohort Study

BACKGROUND

The majority of studies suggesting that online hemodiafiltration reduces the risk of mortality compared to hemodialysis (HD) have been performed in dialysis-prevalent populations. In this report, we conducted an epidemiologic study of mortality in incident dialysis patients, comparing post-dilution online hemodiafiltration and high-flux HD, with propensity score matching (PSM) used to correct indication bias.

METHODS

Our study cohort comprised 3,075 incident dialysis patients treated in 64 Spanish Fresenius Medical Care clinics between January 2009 and December 2012. The primary outcome of this study was to investigate the impact of the type of renal replacement on all-cause mortality. An analysis of cardiovascular mortality was defined as the secondary outcome. To achieve these objectives, patients were followed until December 2016. Patients were categorized as high-flux HD patients if they underwent this treatment exclusively. If >90% of their treatment was with online hemodiafiltration, then the patient was grouped to that modality.

RESULTS

After PSM, a total of 1,012 patients were matched. Compared with patients on high-flux HD, those on online hemodiafiltration received a median replacement volume of 23.45 (interquartile range 21.27-25.51) L/session and manifested 24 and 33% reductions in all-cause and cardiovascular mortality (all-cause mortality hazards ratio [HR] 0.76, 95% CI 0.62-0.94 [p = 0.01]; and cardiovascular mortality HR 0.67, 95% CI 0.50-0.90 [p = 0.008]).

CONCLUSIONS

This study shows that post-dilution online hemodiafiltration reduces all-cause and cardiovascular mortality compared to high-flux HD in an incident HD population.