Multipass haemodialysis: a novel dialysis modality

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

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

Analytical solution of phosphate kinetics for hemodialysis

Chronic kidney diseases imply an ongoing need to remove toxins, with hemodialysis as the preferred treatment modality. We derive analytical expressions for phosphate clearance during dialysis, the single pass (SP) model corresponding to a standard clinical hemodialysis and the multi pass (MP) model, where dialysate is recycled and therefore makes a smaller clinical setting possible such as a transportable dialysis suitcase. For both cases we show that the convective contribution to the dialysate is negligible for the phosphate kinetics and derive simpler expressions. The SP and MP models are calibrated to clinical data of ten patients showing consistency between the models and provide estimates of the kinetic parameters. Immediately after dialysis a rebound effect is observed. We derive a simple formula describing this effect which is valid both posterior to SP or MP dialysis. The analytical formulas provide explanations to observations of previous clinical studies.

Bayesian parameter estimation for phosphate dynamics during hemodialysis

Hyperphosphatemia in patients with renal failure is associated with increased vascular calcification and mortality. Hemodialysis is a conventional treatment for patients with hyperphosphatemia. Phosphate kinetics during hemodialysis may be described by a diffusion process and modeled by ordinary differential equations. We propose a Bayesian model approach for estimating patient-specific parameters for phosphate kinetics during hemodialysis. The Bayesian approach allows us to both analyze the full parameter space using uncertainty quantification and to compare two types of hemodialysis treatments, the conventional single-pass and the novel multiple-pass treatment. We validate and test our models on synthetic and real data. The results show limited identifiability of the model parameters when only single-pass data are available, and that the Bayesian model greatly reduces the relative standard deviation compared to existing estimates. Moreover, the analysis of the Bayesian models reveal improved estimates with reduced uncertainty when considering consecutive sessions and multiple-pass treatment compared to single-pass treatment.

Clearance of Sclerostin, Osteocalcin, Fibroblast Growth Factor 23, and Osteoprotegerin by Dialysis

INTRODUCTION

Fibroblast growth factor (FGF23), sclerostin, osteocalcin, and osteoprotegerin are important factors that control mineral bone metabolism. End-stage renal disease is associated with the pronounced dysregulation of mineral bone metabolism; however, the impact and clearance of mineral bone metabolism factors during dialysis remain largely undescribed.

METHODS

In a cross-sectional study, 10 chronic hemodialysis patients were treated with hemodialysis for 8 h using a high-flux filter and a dialysate bath of 50% calculated total body water continuously recycled at a rate of 500 mL/min. Plasma and dialysate concentrations of FGF23, sclerostin, osteoprotegerin, and osteocalcin were measured at 1, 2, 4, 6, and 8 h permitting the estimation of dialysis clearance.

RESULTS

Clearance of FGF23 was 7.7 mL/min, of sclerostin was 7.6 mL/min, of osteoprotegerin was 1.2 mL/min, and of osteocalcin was 19.7 mL/min. Clearance of FGF23 was correlated to sclerostin and osteoprotegerin clearance and also to the ultrafiltration rate. Although, osteocalcin blood concentrations decreased during dialysis, they rebounded within 6 h. Overall, no significant changes in blood concentrations of the measure mineral bone metabolism factors were observed.

CONCLUSIONS

The intradialytic clearance of osteocalcin, FGF23, sclerostin, and osteoprotegerin occurs; however, only clearance of FGF23 is directly correlated with the ultrafiltration rate. The effects of dialytic clearance on mineral bone metabolism are, however, uncertain and intradialytic plasma concentrations of the studied substrates remained largely unchanged.

Cost of renal replacement: how to help as many as possible while keeping expenses reasonable?

The treatment of kidney diseases consumes a substantial amount of the health budget for a relatively small fraction of the overall population. If the nephrological community and society do not develop mechanisms to contain those costs, it will become impossible to continue assuring optimal outcomes and quality of life while treating all patients who need it. In this article, we describe several mechanisms to maintain sustainability of renal replacement therapy. These include (i) encouragement of transplantation after both living and deceased donation; (ii) stimulation of alternative dialysis strategies besides classical hospital haemodialysis, such as home haemodialysis, peritoneal dialysis or self-care and necessitating less reimbursement; (iii) promotion of educational activities guiding the patients towards therapies that are most suited for them; (iv) consideration of one or more of cost containment incentives such as bundling of reimbursement (if not affecting quality of the treatment), timely patient referral, green dialysis, start of dialysis based on clinical necessity rather than renal function parameters and/or prevention of CKD or its progression; (v) strategically planned adaptations to the expected growth of the ageing population in need of renal replacement; (vi) the necessity for support of research in the direction of helping as large as possible patient populations for acceptable costs; and (vii) the need for more patient-centred approaches. We also extend the discussion to the specific situation of kidney diseases in low- and middle-income countries. Finally, we point to the dramatic differences in accessibility and reimbursement of different modalities throughout Europe. We hope that this text will offer a framework for the nephrological community, including patients and nurses, and the concerned policy makers and caregivers on how to continue reaching all patients in need of renal replacement for affordable expenses.

Protein-bound solute removal during extended multipass versus standard hemodialysis

Background

Multipass hemodialysis (MPHD) is a recently described dialysis modality, involving the use of small volumes of dialysate which are repetitively recycled. Dialysis regimes of 8 hours for six days a week using this device result in an increased removal of small water soluble solutes and middle molecules compared to standard hemodialysis (SHD). Since protein-bound solutes (PBS) exert important pathophysiological effects, we investigated whether MPHD results in improved removal of PBS as well.

Methods

A cross-over study (Clinical Trial NCT01267760) was performed in nine stable HD patients. At midweek a single dialysis session was performed with either 4 hours SHD using a dialysate flow of 500 mL/min or 8 hours MPHD with a dialysate volume of 50% of estimated body water volume. Blood and dialysate samples were taken every hour to determine concentrations of p-cresylglucuronide (PCG), hippuric acid (HA), indole acetic acid (IAA), indoxyl sulfate (IS), and p-cresylsulfate (PCS). Dialyser extraction ratio, reduction ratio, and solute removal were calculated for these solutes.

Results

Already at 60 min after dialysis start, the extraction ratio in the hemodialyser was a factor 1.4-4 lower with MPHD versus SHD, resulting in significantly smaller reduction ratios and lower solute removal within a single session. Even when extrapolating our findings to 3 times 4 h SHD and 6 times 8 h MPHD per week, the latter modality was at best similar in terms of total solute removal for most protein-bound solutes, and worse for the highly protein-bound solutes IS and PCS. When efficiency was calculated as solute removal/litre of dialysate used, MPHD was found superior to SHD.

Conclusion

When high water consumption is a concern, a treatment regimen of 6 times/week 8 h MPHD might be an alternative for 3 times/week 4 h SHD, but at the expense of a lower total solute removal of highly protein-bound solutes.

Improving outcomes by changing hemodialysis practice patterns

PURPOSE OF REVIEW

This review examines recent advances in understanding of how clinical outcomes for hemodialysis patients may be improved by achieving longer or more frequent treatment times, lower ultrafiltration rates (UFRs), improving nutritional status, and individualizing dialysate composition. This review also discusses the controversy related to timing of dialysis initiation.

RECENT FINDINGS

Many observational studies and several randomized controlled trials indicate longer dialysis treatment times, particularly nocturnal dialysis, and/or more frequent dialysis improve morbidity and mortality. Recent evidence also suggests that lower UFR and more consistent achievement of 'dry weight' may help minimize the damage from myocardial stunning and chronic volume overload that occurs in the majority of patients who receive conventional hemodialysis during the day with a standard schedule of 3-5 h, 3 times a week. Other aspects of the dialysis procedure such as appropriate estimated glomerular filtration rate for dialysis initiation and individualizing dialysate composition may also minimize cardiovascular risk. Finally, several studies have highlighted the benefits of oral nutritional supplementation (ONS) during dialysis.

SUMMARY

Greater treatment times per week with slower UFR, consistent attainment of 'dry weight', individualized dialysate prescriptions, and administration of ONS to malnourished patients are likely to reduce hospitalizations and improve survival in this high-risk population of end-stage renal disease patients.