Abstract
In the past decade, a new class of hemodialysis (HD) membranes (high retention onset class) became available for clinical use. The high cutoff (HCO) and the medium cutoff (MCO) membranes have wider pores and more uniformity in pore size, allowing an increased clearance of uremic toxins. Owing to the mechanism of backfiltration/internal filtration, middle molecules are dragged by the convective forces, and no substitution solution is needed. The HCO dialyzer is applied in septic patients with acute kidney injury requiring continuous kidney replacement therapy. The immune response is modulated thanks to the removal of inflammatory mediators. Another current application for the HCO dialyzer is in hematology, for patients on HD secondary to myeloma-kidney, since free light chains are more efficiently removed with the HCO membrane, reducing their deleterious effect on the renal tubules. In its turn, the MCO dialyzer is used for maintenance HD patients. A myriad of clinical trials published in the last three years consistently demonstrates the ability of this membrane to remove uremic toxins more efficiently than the high-flux membrane, an evolutionary disruption in the HD standard of care. Safety concerns regarding albumin loss as well as blood contamination from pyrogens in the dialysate have been overcome. In this update article, we explore the rise of new dialysis membranes in the light of the scientific evidence that supports their use in clinical practice.
Highlights
A typical adult dialyzer has around 15,000 hollow fibers tightly packet, forming a compact bundle placed inside a 20 cm plastic tube
This was a proof of concept study, demonstrating that the permeability of the medium cutoff (MCO) and high cutoff (HCO) membranes to middle molecules favors a one-way direction since the external layer of these membranes and the tridimensional configuration repeal middle molecules and only allow the entrance of small molecules dragged in by the backfiltration mechanism (Figure 2)
The REMOVAL-HD trial[35] showed a higher reduction ratio (RR) and a sustained reduction in the pre-dialysis concentration of free light chains (FLC) favoring MCOHD over HF-HD. It is highly debatable if the better clinical outcomes achieved with HF-HDF13 can be extrapolated for MCO-HD, based on the fact that the removal of middle molecules is similar for both modalities
Summary
A typical adult dialyzer has around 15,000 hollow fibers tightly packet, forming a compact bundle placed inside a 20 cm plastic tube. The results demonstrated a similar concentration of endotoxins in the blood compartment, irrespective of the membrane This was a proof of concept study, demonstrating that the permeability of the MCO and HCO membranes to middle molecules favors a one-way direction since the external layer of these membranes and the tridimensional configuration repeal middle molecules and only allow the entrance of small molecules dragged in by the backfiltration mechanism (Figure 2). The REMOVAL-HD trial[35] showed a higher RR and a sustained reduction in the pre-dialysis concentration of FLC favoring MCOHD over HF-HD It is highly debatable if the better clinical outcomes achieved with HF-HDF13 can be extrapolated for MCO-HD, based on the fact that the removal of middle molecules is similar for both modalities. The possibility of utilizing the MCO filter for CKRT seems appealing as it merges the advantages of CVVHD (increased filter life span) and CVVH/CVVHDF (higher clearance of inflammatory mediators)[39]
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