Expanded Hemodialysis as an Alternative to Hemodiafiltration
Expanded hemodialysis is a new type of therapy that effectively removes middle molecules from the blood of dialysis patients. The aim of the Spanish authors was to compare its efficiency with hemodiafiltration in terms of clearance of middle molecules in an open randomized clinical study.
Introduction
The effectiveness of blood purification by hemodialysis (HD) depends on vascular access, type of dialyzer membrane, duration of treatment, and blood flow rate. The choice of membrane is particularly important for the effective removal of medium-sized uremic toxins (MM – middle molecular uremic toxins), for which the permeability characteristics of the membrane are key. The most studied MM is β2-microglobulin (β2m) with a molecular weight of 11.8 kDA, which plays a role in the development of dialysis-related amyloidosis and is associated with an increased risk of mortality in dialysis patients.
Options for Addressing Long-term Dialysis Complications
Recent advancements have led to the development of MCO membranes (medium cut-off dialysis) designed for expanded hemodialysis (HDx), which improves the clearance of large MM without the need for external fluid replacement, as is the case with hemodiafiltration (HDF). Previous studies have confirmed the safety of long-term HDx, and initial data suggest its beneficial impact on hospitalization rates, medication usage, and costs compared to conventional HD.
Methodology and Course of the Study
The efficacy of HDx and HDF was compared in an open, prospective, randomized study with dialysis patients aged 18–80 years, lasting 24 weeks. Patients were randomized (in a 1:1 ratio) either to transition to HDx or to continue with HDF.
HDx was performed using the Theranova 500 dialyzer (polyarylethersulfone/polyvinylpyrrolidone membrane, surface area 2.0 m2). HDF was conducted in post-dilution mode using the Polyflux 170H dialyzer (polyarylethersulfone/polyamide/polyvinylpyrrolidone membrane, surface area 1.7 m2) with a target convection volume of at least 23 l.
Results
HDx was initiated in 21 patients and 22 continued with HDF.
The study measured the removal of 4 large middle molecules (FGF-23, kappa FLC, lambda FLC, and YKL-40), whose high plasma levels are predictors of adverse outcomes in patients with chronic kidney disease (CKD). HDx exhibited a greater reduction ratio for YKL-40, while the reduction ratios for β2m, FGF-23, and free light chains were comparable in both groups. No differences were found between the HDx and HDF groups in terms of changes in inflammatory biomarker levels (IL-6, CRP, PTX3) during dialysis. Changes in markers of inflammation, albumin, fibrinogen, hemoglobin, parathyroid hormone (PTH), and phosphorus from the start of the study to weeks 12 and 24 did not differ between groups. A decrease in the need for erythropoiesis-stimulating agents was observed in the HDx group.
Adverse events were reported in 37 (86%) patients in total (18 in the HDx group and 19 in the HDF group). The most common were hypotension, muscle cramps, and hypertension.
Conclusion
As suggested by this study, expanded hemodialysis using the MCO membrane removes large middle molecules at least as effectively as hemodiafiltration. Expanded hemodialysis showed a trend towards lower consumption of erythropoiesis-stimulating agents without achieving worse clinical efficacy than hemodiafiltration. Due to its easy implementation, fewer equipment requirements, and lower costs, expanded hemodialysis appears to be an attractive option for long-term dialysis.
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Source: Hadad-Arrascue F., Nilsson L.-G., Rivera A. S. et al. Expanded hemodialysis as effective alternative to on-line hemodiafiltration: a randomized mid-term clinical trial. Ther Apher Dial 2021 Jun 14, doi: 10.1111/1744-9987.13700 [Epub ahead of print].
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