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

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.

Rediscovering Beta-2 Microglobulin As a Biomarker across the Spectrum of Kidney Diseases

There is currently an unmet need for better biomarkers across the spectrum of renal diseases. In this paper, we revisit the role of beta-2 microglobulin (β₂M) as a biomarker in patients with chronic kidney disease and end-stage renal disease. Prior to reviewing the numerous clinical studies in the area, we describe the basic biology of β₂M, focusing in particular on its role in maintaining the serum albumin levels and reclaiming the albumin in tubular fluid through the actions of the neonatal Fc receptor. Disorders of abnormal β₂M function arise as a result of altered binding of β₂M to its protein cofactors and the clinical manifestations are exemplified by rare human genetic conditions and mice knockouts. We highlight the utility of β₂M as a predictor of renal function and clinical outcomes in recent large database studies against predictions made by recently developed whole body population kinetic models. Furthermore, we discuss recent animal data suggesting that contrary to textbook dogma urinary β₂M may be a marker for glomerular rather than tubular pathology. We review the existing literature about β₂M as a biomarker in patients receiving renal replacement therapy, with particular emphasis on large outcome trials. We note emerging proteomic data suggesting that β₂M is a promising marker of chronic allograft nephropathy. Finally, we present data about the role of β₂M as a biomarker in a number of non-renal diseases. The goal of this comprehensive review is to direct attention to the multifaceted role of β₂M as a biomarker, and its exciting biology in order to propose the next steps required to bring this recently rediscovered biomarker into the twenty-first century.

Treatment tolerance and patient-reported outcomes favor online hemodiafiltration compared to high-flux hemodialysis in the elderly

Large cohort studies suggest that high convective volumes associated with online hemodiafiltration may reduce the risk of mortality/morbidity compared to optimal high-flux hemodialysis. By contrast, intradialytic tolerance is not well studied. The aim of the FRENCHIE (French Convective versus Hemodialysis in Elderly) study was to compare high-flux hemodialysis and online hemodiafiltration in terms of intradialytic tolerance. In this prospective, open-label randomized controlled trial, 381 elderly chronic hemodialysis patients (over age 65) were randomly assigned in a one-to-one ratio to either high-flux hemodialysis or online hemodiafiltration. The primary outcome was intradialytic tolerance (day 30-day 120). Secondary outcomes included health-related quality of life, cardiovascular risk biomarkers, morbidity, and mortality. During the observational period for intradialytic tolerance, 85% and 84% of patients in high-flux hemodialysis and online hemodiafiltration arms, respectively, experienced at least one adverse event without significant difference between groups. As exploratory analysis, intradialytic tolerance was also studied, considering the sessions as a statistical unit according to treatment actually received. Over a total of 11,981 sessions, 2,935 were complicated by the occurrence of at least one adverse event, with a significantly lower occurrence in online hemodiafiltration with fewer episodes of intradialytic symptomatic hypotension and muscle cramps. By contrast, health-related quality of life, morbidity, and mortality were not different in both groups. An improvement in the control of metabolic bone disease biomarkers and β2-microglobulin level without change in serum albumin concentration was observed with online hemodiafiltration. Thus, overall outcomes favor online hemodiafiltration over high-flux hemodialysis in the elderly.

Is Hemodialysis Patient Survival Dependent upon Small Solute Clearance (Kt/V)?: If So How Can Kt/V be Adjusted to Prevent Under Dialysis in Vulnerable Groups?

Small solute clearance achieved during a single hemodialysis session has been traditionally evaluated by urea clearance, normalized for total body water (Kt/Vurea) for more than 30 years. By consensus, the target sessional KtVurea for thrice weekly treatments has been increased from 0.9 to 1.2 over the years. Although this is supported by observational studies, there is a fundamental lack of prospective studies to support this threshold target. In clinical practice achieving sessional Kt/Vurea targets are most closely followed in the US. Yet there appears to be a paradox in that by following Kt/Vurea targets in the US hemodialysis patient survival is better for men and the obese, the opposite of what is seen in the general population. Delivery of a lower dose of hemodialysis to women and smaller men can be explained by underestimation of total body water. The advent of bioimpedance techniques which can measure both body water and body composition will potentially allow a rescaling and re-evaluation of the importance of small solute clearances (Kt/Vurea) in the hemodialysis patient population.

A Randomized, Single-Blind, Crossover Trial of Recovery Time in High-Flux Hemodialysis and Hemodiafiltration

Background

The choice between hemodiafiltration (HDF) or high-flux hemodialysis (HD) to treat end-stage kidney disease remains a matter of debate. The duration of recovery time after treatment has been associated with mortality, affects quality of life, and may therefore be important in informing patient choice. We aimed to establish whether recovery time is influenced by treatment with HDF or HD.

Study Design

Randomized patient-blinded crossover trial.

Settings & Participants

100 patients with end-stage kidney disease were enrolled from 2 satellite dialysis units in Glasgow, United Kingdom.

Intervention

8 weeks of HD followed by 8 weeks of online postdilution HDF or vice versa.

Outcomes

Posttreatment recovery time, symptomatic hypotension events, dialysis circuit clotting events, and biochemical parameters.

Measurements

Patient-reported recovery time in minutes, incidence of adverse events during treatments, hematology and biochemistry results, quality-of-life questionnaire.

Results

There was no overall difference in recovery time between treatments (medians for HDF vs HD of 47.5 [IQR, 0-240] vs 30 [IQR, 0-210] minutes, respectively; P = 0.9). During HDF treatment, there were significant increases in rates of symptomatic hypotension (8.0% in HDF vs 5.3% in HD; relative risk [RR], 1.52; 95% CI, 1.2-1.9; P < 0.001) and intradialytic tendency to clotting (1.8% in HDF vs 0.7% in HD; RR, 2.7; 95% CI, 1.5-5.0; P = 0.002). Serum albumin level was significantly lower during HDF (3.2 vs 3.3 g/dL; P < 0.001). Health-related quality-of-life scores were equivalent.

Limitations

Single center; mean achieved HDF convection volume, 20.6 L.

Conclusions

Patients blinded to whether they were receiving HD or HDF in a randomized controlled crossover study reported similar posttreatment recovery times and health-related quality-of-life scores.

Intradialytic Cardiac Magnetic Resonance Imaging to Assess Cardiovascular Responses in a Short-Term Trial of Hemodiafiltration and Hemodialysis

Hemodynamic stress during hemodialysis (HD) results in recurrent segmental ischemic injury (myocardial stunning) that drives cumulative cardiac damage. We performed a fully comprehensive study of the cardiovascular effect of dialysis sessions using intradialytic cardiac magnetic resonance imaging (MRI) to examine the comparative acute effects of standard HD versus hemodiafiltration (HDF) in stable patients. We randomly allocated 12 patients on HD (ages 32-72 years old) to either HD or HDF. Patients were stabilized on a modality for 2 weeks before undergoing serial cardiac MRI assessment during dialysis. Patients then crossed over to the other modality and were rescanned after 2 weeks. Cardiac MRI measurements included cardiac index, stroke volume index, global and regional contractile function (myocardial strain), coronary artery flow, and myocardial perfusion. Patients had mean±SEM ultrafiltration rates of 3.8±2.9 ml/kg per hour during HD and 4.4±2.5 ml/kg per hour during HDF (P=0.29), and both modalities provided a similar degree of cooling. All measures of systolic contractile function fell during HD and HDF, with partial recovery after dialysis. All patients experienced some degree of segmental left ventricular dysfunction, with severity proportional to ultrafiltration rate and BP reduction. Myocardial perfusion decreased significantly during HD and HDF. Treatment modality did not influence any of the cardiovascular responses to dialysis. In conclusion, in this randomized, crossover study, there was no significant difference in the cardiovascular response to HDF or HD with cooled dialysate as assessed with intradialytic MRI.

Cost-effectiveness analysis of online hemodiafiltration versus high-flux hemodialysis

Background

Clinical studies suggest that hemodiafiltration (HDF) may lead to better clinical outcomes than high-flux hemodialysis (HF-HD), but concerns have been raised about the cost-effectiveness of HDF versus HF-HD. Aim of this study was to investigate whether clinical benefits, in terms of longer survival and better health-related quality of life, are worth the possibly higher costs of HDF compared to HF-HD.

Methods

The analysis comprised a simulation based on the combined results of previous published studies, with the following steps: 1) estimation of the survival function of HF-HD patients from a clinical trial and of HDF patients using the risk reduction estimated in a meta-analysis; 2) simulation of the survival of the same sample of patients as if allocated to HF-HD or HDF using three-state Markov models; and 3) application of state-specific health-related quality of life coefficients and differential costs derived from the literature. Several Monte Carlo simulations were performed, including simulations for patients with different risk profiles, for example, by age (patients aged 40, 50, and 60 years), sex, and diabetic status. Scatter plots of simulations in the cost-effectiveness plane were produced, incremental cost-effectiveness ratios were estimated, and cost-effectiveness acceptability curves were computed.

Results

An incremental cost-effectiveness ratio of €6,982/quality-adjusted life years (QALY) was estimated for the baseline cohort of 50-year-old male patients. Given the commonly accepted threshold of €40,000/QALY, HDF is cost-effective. The probabilistic sensitivity analysis showed that HDF is cost-effective with a probability of ~81% at a threshold of €40,000/QALY. It is fundamental to measure the outcome also in terms of quality of life. HDF is more cost-effective for younger patients.

Conclusion

HDF can be considered cost-effective compared to HF-HD.

Technology innovation for patients with kidney disease

The loss of kidney function is a life-changing event leading to life-long dependence on healthcare. Around 5000 people are diagnosed with kidney failure every year. Historically, technology in renal medicine has been employed for replacement therapies. Recently, a lot of emphasis has been placed on technologies that aid early identification and prevent progression of kidney disease, while at the same time empowering affected individuals to gain control over their chronic illness. There is a shift in diversity of technology development, driven by collaborative innovation initiatives such the National Institute's for Health Research Healthcare Technology Co-operative for Devices for Dignity. This has seen the emergence of the patient as a key figure in designing technologies that are fit for purpose, while business involvement has ensured uptake and sustainability of these developments. An embodiment of this approach is the first successful Small Business Research Initiative in the field of renal medicine in the UK.

Hemodiafiltration Versus Hemodialysis and Survival in Patients With ESRD: The French Renal Epidemiology and Information Network (REIN) Registry

BACKGROUND

Recent randomized trials report that mortality is lower with high-convection-volume hemodiafiltration (HDF) than with hemodialysis (HD).

STUDY DESIGN

We used data from the French national Renal Epidemiology and Information Network (REIN) registry to investigate trends in HDF use and its relationship with mortality in the total population of incident dialysis patients.

SETTING & PARTICIPANTS

The study included those who initiated HD therapy from January 1, 2008, through December 31, 2011, and were dialyzed for more than 3 months; follow-up extended to the end of 2012.

FACTOR

HDF use at the patient and facility level.

OUTCOMES

All-cause and cardiovascular mortality, using Cox models to estimate HRs of HDF as time-dependent covariate at the patient level, with age as time scale and fully adjusted for comorbid conditions and laboratory data at baseline, catheter use, and facility type as time-dependent covariates. Analyses completed by Cox models for HRs of the facility-level exposure to HDF updated yearly.

RESULTS

Of 28,407 HD patients, 5,526 used HDF for a median of 1.2 (IQR, 0.9-1.9) years; 2,254 of them used HDF exclusively. HRs for all-cause and cardiovascular mortality associated with HDF use were 0.84 (95% CI, 0.77-0.91) and 0.73 (95% CI, 0.61-0.88), respectively. In patients treated exclusively with HDF, these HRs were 0.77 (95% CI, 0.67-0.87) and 0.66 (95% CI, 0.50-0.86). At the facility level, increasing the percentage of patients using HDF from 0% to 100% was associated with HRs for all-cause and cardiovascular mortality of 0.87 (95% CI, 0.77-0.99) and 0.72 (95% CI, 0.54-0.96), respectively.

LIMITATIONS

Observational study.

CONCLUSIONS

Whether analyzed as a patient- or facility-level predictor, HDF treatment was associated with better survival.

Cost-Effectiveness Analysis of High-Efficiency Hemodiafiltration Versus Low-Flux Hemodialysis Based on the Canadian Arm of the CONTRAST Study

AIM

The aim of this study was to assess the cost effectiveness of high-efficiency on-line hemodiafiltration (OL-HDF) compared with low-flux hemodialysis (LF-HD) for patients with end-stage renal disease (ESRD) based on the Canadian (Centre Hospitalier de l'Université de Montréal) arm of a parallel-group randomized controlled trial (RCT), the CONvective TRAnsport STudy.

METHODS

An economic evaluation was conducted for the period of the RCT (74 months). In addition, a Markov state transition model was constructed to simulate costs and health benefits over lifetime. The primary outcome was costs per quality-adjusted life-year (QALY) gained. The analysis had the perspective of the Quebec public healthcare system.

RESULTS

A total of 130 patients were randomly allocated to OL-HDF (n = 67) and LF-HD (n = 63). The cost-utility ratio of OL-HDF versus LF-HD was Can$53,270 per QALY gained over lifetime. This ratio was fairly robust in the sensitivity analysis. The cost-utility ratio was lower than that of LF-HD compared with no treatment (immediate death), which was Can$93,008 per QALY gained.

CONCLUSIONS

High-efficiency OL-HDF can be considered a cost-effective treatment for ESRD in a Canadian setting. Further research is needed to assess cost effectiveness in other settings and healthcare systems.

Haemodiafiltration and mortality in end-stage kidney disease patients: a pooled individual participant data analysis from four randomized controlled trials

BACKGROUND

Mortality rates remain high for haemodialysis (HD) patients and simply increasing the HD dose to remove more small solutes does not improve survival. Online haemodiafiltration (HDF) provides additional clearance of larger toxins compared with standard HD. Randomized controlled trials (RCTs) comparing HDF with conventional HD on all-cause and cause-specific mortality in end-stage kidney disease (ESKD) patients reported inconsistent results and were at high risk of bias. We conducted a pooled individual participant data analysis of RCTs to provide the most reliable evidence to date on the effects of HDF on mortality outcomes in ESKD patients.

METHODS

Individual participant data were used from four trials that compared online HDF with HD and were designed to examine the effects of HDF on mortality endpoints. Bias by informative censoring of patients was resolved. Hazard ratios (HRs) and 95% confidence intervals (95% CI) comparing the effect of online HDF versus HD on all-cause and cause-specific mortality were calculated using the Cox proportional hazard regression models. The relationship between convection volume and the study outcomes was examined by delivered convection volume standardized to body surface area.

RESULTS

After a median follow-up of 2.5 years (Q1-Q3: 1.9-3.0), 769 of the 2793 participants had died (292 cardiovascular deaths). Online HDF reduced the risk of all-cause mortality by 14% (95% CI: 1%; 25%) and cardiovascular mortality by 23% (95% CI: 3%; 39%). There was no evidence for a differential effect in subgroups. The largest survival benefit was for patients receiving the highest delivered convection volume [>23 L per 1.73 m(2) body surface area (BSA) per session], with a multivariable-adjusted HR of 0.78 (95% CI: 0.62; 0.98) for all-cause mortality and 0.69 (95% CI: 0.47; 1.00) for cardiovascular disease mortality.

CONCLUSIONS

This pooled individual participant analysis on the effects of online HDF compared with conventional HD indicates that online HDF reduces the risk of mortality in ESKD patients. This effect holds across a variety of important clinical subgroups of patients and is most pronounced for those receiving a higher convection volume normalized to BSA.

Is There an 'Optimal Dose' of Hemodiafiltration?

BACKGROUND

Retrospective randomized clinical studies have shown that online hemodiafiltration (OL-HDF) is associated with a lower risk reduction of mortality than standard hemodialysis.

SUMMARY

In all of these large randomized studies, the convective volume seemed to be an important issue, but the optimal OL-HDF dose has not yet been defined. This article, to make a EUDIAL working group position, reviews the association between survival and convective volume, the minimum recommended replacement volume, the importance of the infusion flow rate, and the main limiting factors in achieving a high convective volume. Finally, the article discusses whether the convective dose should be normalized to body size. Key Messages: At present, there is sufficient scientific evidence to indicate that OL-HDF treatment reduces mortality risk and that it should be the first-line option in hemodialysis patients. It seems reasonable to recommend that patients should receive the highest possible convective dose and that the largest possible blood flow should be used to obtain the highest possible infusion flow rate. Based on the results of secondary analyses of the main clinical trials, the current recommendation of the optimal dose of OL-HDF, in the postdilutional mode and on a thrice-weekly treatment schedule, would be a convective volume higher than 23 liters/session. There is insufficient scientific evidence to recommend that the convective dose should be normalized to body size.

Current Evidence in Haemodiafiltration

BACKGROUND

Standard low-flux haemodialysis (HD) is not very efficacious, and patient morbidity and mortality rates are still very high. According to the initial study design, the MPO study reported that high-flux HD (hf-HD) showed a significant 37% relative risk reduction of mortality in patients with serum albumin ≤4 g/dl; online haemodiafiltration (HDF) is considered the most efficient technique of using high-flux membranes, as clearances of small solutes, like urea, are higher than in haemofiltration and clearances of middle solutes, like β2-microglobulin, are higher than in hf-HD.

SUMMARY

Three randomized trials have recently been published analysing the effect of online HDF on mortality. Two trials were unable to demonstrate a positive effect of HDF on survival, while 1 showed a significantly better survival in patients randomized to HDF in comparison to those randomized to hf-HD. It is intriguing that post hoc analyses of these 3 studies showed that the patients randomized to online HDF who received the highest convection volumes had a lower risk of mortality and cardiovascular events than those randomized to HD. Four very recently published meta-analyses have shown inconsistent results concerning the effect of convective treatments in improving patient general and cardiovascular survival, while they have consistently shown a significant reduction of the intradialytic symptomatic hypotension in patients treated with convective techniques in comparison with those treated with prevalent diffusive ones. Key Messages: The results of the randomized trials on the effect of HDF in improving patient survival are inconclusive. Moreover, trials specifically designed for testing the effect of increased convection of online HDF on patient survival and morbidity in comparison to patients treated with hf-HD are still awaited.

Kt/V (and especially its modifications) remains a useful measure of hemodialysis dose

Removal of small molecular weight solutes shows a strong relationship to hemodialysis outcomes. In contrast, survival with high-flux dialysis or hemodiafiltration is only slightly better than with low-flux hemodialysis. Despite laboratory evidence regarding toxicity of protein-bound uremic solutes, few data exist showing that increased removal of this class of molecules impacts outcomes. In the FHN trials, there was no effect of frequent dialysis, including frequent and long dialysis, on nutrition or control of anemia, outcomes expected to be sensitive to uremic toxin removal; the main benefit appeared to be better volume control. Scaling of hemodialysis dose to total body water may not be optimal. Kt/V scaling to body surface area and use of a continuous measure such as standard Kt/V reduces the likelihood of underdialysis of small patients, including children, and women. Minimum hemodialysis time may best be considered in respect to ultrafiltration rate, and a maximum target ultrafiltration rate unscaled to body size may be optimal. Intensive, extended dialysis may cause adverse effects to residual kidney function, and more information needs to be collected to better understand how urine volume modifies dose requirements, and how to maximize the chances of preserving residual kidney function.

Treatment Time or Convection Volume in HDF: What Drives the Reduced Mortality Risk?

BACKGROUND/AIMS

Treatment time is associated with survival in hemodialysis (HD) patients and with convection volume in hemodiafiltration (HDF) patients. High-volume HDF is associated with improved survival. Therefore, we investigated whether this survival benefit is explained by treatment time.

METHODS

Participants were subdivided into four groups: HD and tertiles of convection volume in HDF. Three Cox regression models were fitted to calculate hazard ratios (HRs) for mortality of HDF subgroups versus HD: (1) crude, (2) adjusted for confounders, (3) model 2 plus mean treatment time. As the only difference between the latter models is treatment time, any change in HRs is due to this variable.

RESULTS

114/700 analyzed individuals were treated with high-volume HDF. HRs of high-volume HDF are 0.61, 0.62 and 0.64 in the three models, respectively (p values <0.05). Confidence intervals of models 2 and 3 overlap.

CONCLUSION

The survival benefit of high-volume HDF over HD is independent of treatment time.

Assessment of dialyzer surface in online hemodiafiltration; objective choice of dialyzer surface area

INTRODUCTION

Online hemodiafiltration (OL-HDF) is currently the most effective technique. Several randomized studies and meta-analyses have observed a reduction in mortality as well as a direct association with convective volume. Currently, it has not been well established whether a larger dialyzer surface area could provide better results in terms of convective and depurative effectiveness. The aim of this study was to assess the effect of larger dialyzer surface areas on convective volume and filtration capacity.

MATERIAL AND METHODS

A total of 37 patients were studied, including 31 men and 6 women, who were in the OL-HDF program using a 5008 Cordiax monitor with auto-substitution. Each patient was analyzed in 3 sessions in which only the dialyzer surface area varied (1.0, 1.4 or 1.8 m(2)). The concentrations of urea (60 Da), creatinine (113 Da), β2-microglobulin (11800 Da), myoglobin (17200 Da) and α1-microglobulin (33000 Da) were determined in serum at the beginning and end of each session in order to calculate the percent reduction of these solutes.

RESULTS

The convective volume reached was 29.8 ± 3.0 with 1.0 m(2), 32.7 ± 3.1 (an increase of 6%) with 1.4 m(2), and 34.7 ± 3.3 L (an increase of 16%) with 1.8 m(2) (p<.001). The increased surface of the dialyzer showed an increase in the dialysis dose as well as urea and creatinine filtration. The percentage of β2m reduction increased from 80.0 ± 5.6 with 1.0 m(2) to 83.2 ± 4.2 with 1.4 m(2) and to 84.3 ± 4.0% with 1.8 m(2). As for myoglobin and a1-microglobulin, significant differences were observed between smaller surface area (1.0 m(2)) 65.6 ± 11 and 20.1 ± 9.3 and the other two surface areas, which were 70.0 ± 8.1 and 24.1 ± 7.1 (1.4 m(2)) and 72.3 ± 8.7 and 28.6 ± 12 (1.8 m(2)).

CONCLUSION

The 40% and 80% increases in surface area led to increased convective volumes of 6 and 16% respectively, while showing minimal differences in both the convective volume as well as the filtration capacity when the CUF was higher than 45 ml/h/mmHg. It is recommended to optimize the performance of dialyzers with the minimal surface area possible when adjusting the treatment prescription.

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

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

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

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

Portable and wearable dialysis devices for the treatment of patients with end-stage kidney failure: Wishful thinking or just over the horizon?

Dialysis is a life-sustaining treatment for patients with end-stage kidney disease. In a different context, for many patients this treatment is the focal point around which their life revolves, not only due to the time spent travelling to and from treatment sessions and the time dedicated to the dialysis treatment itself, but also due to the accompanying dietary and fluid restrictions and medication burden. Wearable and portable dialysis devices could potentially improve patient quality of life by allowing patients to continue with their daily activities of life while undergoing dialysis, as well as by loosening-or removing entirely-dietary and fluid restrictions and reducing pill burden. Advances in nanotechnology manufacturing coupled with advances in electronics and miniaturisation have allowed a new generation of wearable and portable dialysis devices to be developed which are now undergoing large animal and patient clinical trials. We are therefore potentially at a new dawn in the treatment of dialysis patients with the first generation of wearable and portable dialysis devices, which may well revolutionise the treatment and quality of life for patients with end-stage kidney disease.

New insights into the effect of haemodiafiltration on mortality: the Romanian experience

BACKGROUND

Haemodiafiltration (HDF), by successfully removing the larger solutes and protein-bound compounds, may offer a feasible approach to improve dialysis outcomes. Recently, three large, randomized, controlled trials have tested this hypothesis, but only one showed an improved survival associated with HDF treatment, when compared with haemodialysis (HD).

METHODS

This is a retrospective analysis of the entire Romanian dialysed population from the European Clinical Database (EUCLID) Fresenius Medical Care Database. We conducted two types of analysis. First, we used an intention-to-treat approach including all patients who were in dialysis (either HDF or HD) at 1 March 2010--'prevalent cohort analysis'. We then considered only the incident patients who started dialysis (either HDF or HD) after 1 March 2010--'incident cohort analysis'. In both analyses, patients were followed until 31 April 2013.

RESULTS

In the prevalent cohort, we included 1546 patients who were already performing dialysis at the first time point-1322 on HD and 224 on HDF. When compared with HD, HDF treatment was associated with reduced mortality in both univariate and multivariate survival analysis (HR = 0.67, 95% CI 0.46-0.96 and HR = 0.58, 95% CI 0.36-0.93, respectively). In the incident cohort, 2447 patients started dialysis (2181 HD and 266 HDF) during the observation period. Patients in the HDF group maintained a reduced risk for all-cause mortality (HR = 0.20, 95% CI 0.11-0.38 for the univariate and HR = 0.24, 95% CI 0.13-0.46 for the fully adjusted model).

CONCLUSIONS

This study suggests that HDF treatment could reduce all-cause mortality in incident and prevalent patients even after correction for different confounders. Interestingly, an additional survival benefit could be observed in incident patients. However, as with any observational study, there could have been other unmeasured confounders that could have influenced our final results.