Does online high-volume hemodiafiltration offer greater efficiency and sustainability compared with high-flux hemodialysis?

Dive into this study in Clinical Kidney Journal: Does online high-volume hemodiafiltration offer greater efficiency and sustainability compared with high-flux hemodialysis? A detailed simulation analysis anchored in real-world data" by Bernard Canaud et al., selected by the Sustainable Nephrology Task Force of the ERA. Article by Gülay Demirtaṣ Ertan, Member of SNTF and the Social Media Team of ERA.

🌿💧Sustainability in dialysis is crucial!

Let's explore this with the study of Canaud et al., chosen by the Sustainable Nephrology Task Force of the ERA to highlight how optimized post-dilution Hemodiafiltration (HDF) can be a greener alternative to high-flux hemodialysis (HD) in renal replacement therapy.

📈 Recent findings suggest that high-volume HDF outperforms high-flux HD in improving patient outcomes, reducing all-cause mortality by up to 23% (CONVINCE trial).

🧩 The big question 🤔

Does high-volume HDF’s improved efficacy come at the expense of sustainability? Might higher substitution volumes (>23L/session) mean more water and energy use, raising environmental concerns?

🔃 Both HD and HDF require ultrapure water, each dialysis session produces about 320 liters of ultrapure water (QD ranging 300-800 ml/min), but HD machines use only 120–144 L during treatment. This leads to significant wastage due to system processes like rinsing and flushing.

💧In fact, only about 45% of the treated water is utilized during a dialysis session; the rest is discarded. This wastage is consistent across both HD and HDF modalities, highlighting a big area for improvement.

⚖️ In online HDF, a portion of this dialysis fluid (15%–35% of QD, tot) is diverted and used as a substitution fluid (QSUB). This substitution fluid is ultrapure and is infused directly into the patient's bloodstream. In post-dilution mode, the substitution fluid is added after the dialyzer (venous segment).

🔃 Modern HDF machines can optimize water and dialysate consumption by adjusting the dialysate flow to match the blood flow rate (QD/QB ratio) and efficiently managing substitution flow. This maximizes the filtration fraction, enriching dialysate with solutes and reducing dialysis fluid consumption.

💡For instance, lowering the QD/QB ratio in HDF from · 1.4 (QD, tot 520 mL/min, while maintaining the same substitution flow QSUB 105 mL/min; VSUB 25.2 L) to · 1.1 (QD, tot 410 mL/min, while maintaining the same substitution flow QSUB 105 mL/min; VSUB 25.2 L) can reduce water consumption from 125 liters to 99 liters per session, yet still achieve comparable urea clearance to HD!

📈 Real-world data backs this up. A study of over 26,000 patients showed that optimized HDF settings led to effective treatment doses (Kt/V ~1.70) while saving up to 25 liters of dialysis fluid per session compared to standard HD.

🧪 Solute clearance efficiency markers: Blood Extraction Coefficient (BEC), Instantaneous Solute Clearance (K), and Dialysate Saturation Coefficient (DSC). These help compare the effectiveness of HDF vs. HD in removing solutes like urea and β2-microglobulin.

📊 Simulations show that post-dilution HDF is superior to HD in all cases for the two markers selected, reflecting low- (urea) and middle-sized (β2M) molecular weight solutes. This finding holds true despite a significant reduction of dialysis flow through the dialyzer down to 430 mL/min.

🌱 The saturation ratio of the dialysate is key for assessing "green dialysis" efficiency. Postdilution HDF boosts this ratio, indicating better performance and resource conservation. More research is needed to confirm if these benefits hold true across diverse populations with different medical profiles. 🌍🔍

🏆 The takeaway?

The study challenges the notion that HDF consumes more resources and suggests that, with optimal prescription and automated management, post-dilution HDF may be the greener, more efficient dialysis option, offering enhanced solute removal and reduced water usage.

📖 For a deeper dive into this study, check out the full paper here