MCO Membranes: Enhanced Selectivity in High-Flux Class

Most recently developed polyester polymer alloy dialyzer: A new medium cut-off membrane?

BACKGROUND

New versions of the polyester polymer alloy (PEPA) membrane have appeared over the years, with increases in both the pore size and the amount of polyvinylpyrrolidone (PVP) to optimize hydrophilicity performance. This study aimed to assess the efficacy of the most recently developed PEPA dialyzer, the FDY series, in hemodialysis (HD) modality in terms of uremic toxin removal and albumin loss and to compare it with that of several high-flux dialyzers currently used in HD and post-dilution hemodiafiltration (HDF) treatments.

METHODS

A prospective study was carried out in 21 patients. All patients underwent six dialysis sessions with the same routine dialysis parameters; only the dialyzer and/or the dialysis modality varied: FX80 in HD, FDY 180 in HD, Clearum HS17 in HDF, Elisio 19H in HDF, Vitapes 180 in HDF, and FX80 in post-dilution HDF. The reduction ratios (RR) of urea, creatinine, ß2-microglobulin, myoglobin, κFLC, prolactin, α1-microglobulin, α1-acid glycoprotein, λFLC, and albumin were compared intraindividually. Dialysate albumin loss was also measured.

RESULTS

Both membranes FDY and FX80 are high-flux dialyzers and are applied here in high-flux HD. The average RR of β2-microglobulin was slightly lower in the two HD treatments than in the HDF treatments. Comparison of dialysis treatments revealed that the PEPA FDY dialyzer in the HD modality was more effective than the FX80 dialyzer in high-flux HD and was as effective as post-dilution HDF, especially in terms of myoglobin, κFLC, prolactin, α1-microglobulin, and λFLC RRs. The FDY treatments obtained similar albumin RR in blood and slightly higher dialysate albumin loss, although the values were clinically acceptable.

CONCLUSIONS

The most recently developed PEPA dialyzers in the HD modality were as effective as all treatments in the HDF modality and were clearly superior to high-flux helixone HD treatment. These results confirm that this dialyzer should be categorized within the medium cut-off (MCO) membrane classification.

Effect of medium cut-off membranes on Pentosidine and N-(carboxymethyl) lysine levels in uncontrolled diabetic hemodialysis patients

INTRODUCTION

Patients on hemodialysis, especially with diabetes, face elevated cardiovascular events. A major contributor to complications associated with diabetes is advanced glycation end products (AGEs). Removing these compounds is challenging in traditional hemodialysis. Medium-cut-off (MCO) membranes potentially remove toxins without significant albumin loss. This study explored how MCO membranes impact AGEs levels in uncontrolled diabetic patients undergoing hemodialysis.

METHODS

Sixteen patients received MCO membrane dialysis, while others used high-flux (HF) membranes. After 12 sessions, the dialyzers were switched, totaling 24 sessions. Blood samples at trial initiation (T0), session 12 (T1) and session 24 (T2) tested for CML, Pentosidine, laboratory parameters.

RESULTS

Switching dialyzers showed increased albumin with MCO-to-HF and decreased with HF-to-MCO, albeit nonsignificant (p = 0.5/p = 0.1). Patients on MCO had lower albumin levels than HF (p = 0.03/p = 0.6, respectively). Hemodialysis with MCO demonstrated lower levels of CML/Pentosidine compared to HF (p = 0.09/p = 0.9 for CML; p = 0.04/p = 0.3 for Pentosidine). Transitioning to HF led to elevated levels (p = 0.4/p = 0.09 for CML; p = 0.3/p = 0.07 for Pentosidine).

CONCLUSION

MCO dialysis in diabetic individuals notably reduces AGE levels.

Hydrophilic Modification of Dialysis Membranes Sustains Middle Molecule Removal and Filtration Characteristics

While efficient removal of uremic toxins and accumulated water is pivotal for the well-being of dialysis patients, protein adsorption to the dialyzer membrane reduces the performance of a dialyzer. Hydrophilic membrane modification with polyvinylpyrrolidone (PVP) has been shown to reduce protein adsorption and to stabilize membrane permeability. In this study we compared middle molecule clearance and filtration performance of nine polysulfone-, polyethersulfone-, and cellulose-based dialyzers over time. Protein adsorption was simulated in recirculation experiments, while β2-microglobulin clearance as well as transmembrane pressure (TMP) and filtrate flow were determined over time. The results of this study showed that β2-microglobulin clearance (-7.2 mL/min/m2) and filtrate flow (-54.4 mL/min) decreased strongly during the first 30 min and slowly afterwards (-0.7 mL/min/m2 and -6.8 mL/min, respectively, for the next 30 min); the TMP increase (+37.2 mmHg and +8.6 mmHg, respectively) showed comparable kinetics. Across all tested dialyzers, the dialyzer with a hydrophilic modified membrane (FX CorAL) had the highest β2-microglobulin clearance after protein fouling and the most stable filtration characteristics. In conclusion, hydrophilic membrane modification with PVP stabilizes the removal capacity of middle molecules and filtration performance over time. Such dialyzers may have benefits during hemodiafiltration treatments which aim to achieve high exchange volumes.

Trial design of the MOTheR HDx study: a multicenter, open-label, prospective, randomized study to explore the morbidity and mortality in patients dialyzed with the Theranova HDx in comparison with online hemodiafiltration

Background

Dialysis patients have been maintaining a high rate of cardiovascular morbidity and mortality. For this reason, it is to introduce necessary new technical advances in clinical practice. There is a relation between toxins retention and inflammation, mortality and morbidity. Medium cut-off (MCO) membranes are a new generation of membranes that allow the removal of a greater number of medium-sized molecules compared with high-flux hemodialysis (HF-HD), but retaining albumin. MCO membranes have an increased permeability and the presence of internal filtration. Because of these special properties, MCO generated a new concept of therapy called expanded HD (HDx). Until now, online hemodiafiltration (OL-HDF) has demonstrated its superiority, in terms of survival, compared with HF-HD. However, the comparison between OL-HDF and HDx remains an unsolved question.

Methods

The MOTheR HDx study trial (NCT03714386) is an open-label, multicenter, prospective, 1:1 randomized, parallel-group trial designed to evaluate the efficacy and safety of HDx compared with OL-HDF in patients treated for dialysis in Spain for up to 36 months. The main endpoint is to determinate whether HDx is non inferior to OL-HDF at reducing the combined outcome of all-cause death and stroke (ischemic or hemorrhagic), acute coronary syndrome (angina and myocardial infarction), peripheral arterial disease (amputation or revascularization) and ischemic colitis (mesenteric thrombosis).

Results

The trial has already started.

Comparison of the medium cutoff dialyzer and postdilution hemodiafiltration on the removal of small and middle molecule uremic toxins

BACKGROUND

The medium cutoff (MCO) dialyzer increases the removal of several middle molecules more effectively than high-flux hemodialysis (HD). However, comparative data addressing the efficacy and safety of MCO dialyzers vs. postdilution hemodiafiltration (HDF) in Korean patients are lacking.

METHODS

Nine patients with chronic HD were included in this pre-post study. Patients underwent HD with an MCO dialyzer for 4 weeks, followed by a 2-week washout period using a high-flux dialyzer to minimize carryover effects, and then turned over to postdilution HDF for 4 weeks. Reduction ratios and differences in the uremic toxins before and after dialysis were calculated from the MCO dialysis, postdilution HDF, and high-flux HD. In the in vitro study, EA.hy926 cells were incubated with dialyzed serum.

RESULTS

Compared to postdilution HDF, the MCO dialyzer achieved significantly higher reduction ratios for larger middle molecules (myoglobin, kappa free light chain [κFLC], and lambda FLC [λFLC]). Similarly, the differences in myoglobin, κFLC, and λFLC concentrations before and after the last dialysis session were significantly greater in MCO dialysis than in postdilution HDF. The expression of Bax and nuclear factor κB was decreased in the serum after dialysis with the MCO dialyzer than with HDF.

CONCLUSION

Compared with high-volume postdilution HDF, MCO dialysis did not provide greater removal of molecules below 12,000 Da, whereas it was superior in the removal of larger uremic middle molecule toxins in patients with kidney failure. Moreover, these results may be expected to have an anti-apoptotic effect on the human endothelium.

Extracorporeal light-chain elimination in myeloma with simple medium cutoff membrane hemodialysis: a retrospective cohort study

Background

We determined the efficacy of free light chain (FLC) removal by regular dialysis equipment (high-flux filtration) with medium cutoff (MCO) membrane hemodialysis (HD) as an adjuvant treatment to standard chemotherapy for patients with acute kidney injury complicating multiple myeloma (MM) and its impact on further dialysis dependency.

Methods

Sixty patients with acute dialysis-dependent renal failure secondary to MM were treated with MCO-HD (55 patients) or HCO (high cutoff)-HD (5 patients) as a control. FLC serum concentration, total protein, immunoglobulins, and LDH were measured throughout the dialysis therapy. The kidney function of the patients was followed up for 1 year.

Results

The median age was 69 years; 25 female and 35 male patients were enrolled. HD significantly reduced FLC kappa levels in the MCO/HCO group by 58%/84% (MCO/HCO group; p < 0.05) and FLC lambda by 39%/33% (MCO/HCO group; p < 0.05). Single HD data (MCO) showed a relative reduction of 70% in kappa and 37% in lambda FLC concentration, as expected by the different sizes of the light chains. Renal function improved significantly and continuously from starting creatinine 5.7/3.8 mg/dl (MCO/HCO group) before HD to 1.4/2.0 mg/dl (MCO/HCO group; p < 0.001) after 1 year. No significant alteration of total protein, immunoglobulins, and LDH concentrations by HD (HCO and MCO group) was observed. After 1 year, 37 of 60 patients were alive and 34 of them were off dialysis.

Conclusion

FLC elimination with MCO-HD is effective, technically easy, and less cost-intensive as compared with HCO-HD. Kidney function recovery in MM patients is achievable.

High flux novel polymeric membrane for renal applications

Biocompatibility and the ability to mediate the appropriate flux of ions, urea, and uremic toxins between blood and dialysate components are key parameters for membranes used in dialysis. Oxone-mediated TEMPO-oxidized cellulose nanomaterials have been demonstrated to be excellent additives in the production and tunability of ultrafiltration and dialysis membranes. In the present study, nanocellulose ionic liquid membranes (NC-ILMs) were tested in vitro and ex vivo. An increase in flux of up to two orders of magnitude was observed with increased rejection (about 99.6%) of key proteins compared to that of polysulfone (PSf) and other commercial membranes. NC-ILMs have a sharper molecular weight cut-off than other phase inversion polymeric membranes, allowing for high throughput of urea and a uremic toxin surrogate and limited passage of proteins in dialysis applications. Superior anti-fouling properties were also observed for the NC-ILMs, including a > 5-h operation time with no systemic anticoagulation in blood samples. Finally, NC-ILMs were found to be biocompatible in rat ultrafiltration and dialysis experiments, indicating their potential clinical utility in dialysis and other blood filtration applications. These superior properties may allow for a new class of membranes for use in a wide variety of industrial applications, including the treatment of patients suffering from renal disease.

Improved β2-Microglobulin and Phosphorous Removal with Expanded Hemodialysis and Online Hemodiafiltration versus High-Flux Hemodialysis: A Cross-Over Randomized Clinical Trial

INTRODUCTION

Expanded hemodialysis (HDx) is expected to provide enhanced permeability of medium-sized molecules, selective solute retention, and better internal retrofiltration. The primary objective of this study was to compare the efficiency for removal of β2-microglobulin with 3 different extracorporeal therapies (ETs): high-flux hemodialysis (HF), online hemodiafiltration (OL-HDF), and HDx. The secondary objective was to evaluate the efficiency of removal of other uremic toxins, including urea, phosphate, CRP, IL-6, IL-10, TNF-⍺, indoxyl sulfate, and p-cresol.

METHODS

This single-center, randomized, and cross-over study was performed. Patients were randomized to determine the initial modality of treatment, each period lasted 4 weeks and between one modality and another, there was a washout period of 1 week. Reduction ratios (RRs) of different-size molecules and albumin were calculated for the different ET.

RESULTS

Twenty-two patients were included, β2-microglobulin RR was greater during both OL-HDF and HDx as compared to HF (RR 62% vs. 73% vs. 27%, respectively, p = <0.0001), and there was no significant difference between HDx and OL-HDF (p = 0.09). A decrease in serum phosphate levels was observed in the HDx and OL-HDF periods, contrary to an increase in HF (-0.79 mg/dL vs. -1.02 mg/dL vs. + 0.11 mg/dL, respectively, p = <0.0001). There was no difference in RRs of other molecules (BUN, CRP, IL-6, IL-10, TNF-⍺, indoxyl sulfate, and p-Cresol). There was no decrease in serum albumin in any ET.

CONCLUSION

HDx provides enhanced removal of β2-microglobulin and phosphate as compared to HF, and similar efficacy as with OL-HDF. HDx should be considered an alternative to chronic convective therapies.

Medium Cut-Off versus Low-Flux Dialyzers in Hemodialysis Patients with COVID-19: Clinical Outcomes and Reduction in Interleukin-6

INTRODUCTION

The coronavirus disease 2019 (COVID-19) pandemic has caused extensive morbidity and mortality worldwide. Hemodialysis (HD) patients are both vulnerable to COVID-19 infection and tend to suffer greater disease severity and mortality. This retrospective study aimed to compare medium cut-off (MCO) and low-flux (LF) membrane dialyzers in terms of interleukin-6 (IL-6) reduction, change in inflammatory state, intradialytic complications, and mortality in chronic HD patients with COVID-19.

METHOD

HD patients with a confirmed COVID-19 infection were admitted to the hospital for 10-14 days and underwent HD at the COVID-HD unit. Choice of dialyzer membrane used (MCO vs. LF) depended on the primary nephrologist(s). We collected data on demographics, baseline characteristics, laboratory results, diagnosis, treatments, HD prescription, hemodynamic status during HD, and mortality at 14 and 28 days after.

RESULTS

IL-6 reduction ratio (RR) in the MCO group was 9.7 (interquartile range, 71.1) percent, which was significantly higher than that of the LF group (RR, -45.7 [interquartile range, 70.2] percent). The incidence rate of intradialytic hypotension in the MCO group was 3.846 events per 100 dialysis hours (95% confidence interval [CI], 1.954-6.856), which was significantly lower than that of the LF group (9.057; 95% CI, 5.592-13.170). Overall, mortality was not significantly different between the two groups.

CONCLUSION

The MCO membrane was more effective in removing IL-6 and was better tolerated than the LF membrane. Large, randomized controlled trials are required to confirm the relative benefits of the MCO membrane, especially mortality. However, due to the COVID-19 pandemic, our results suggest that the MCO membrane may be beneficial in chronic HD patients with COVID-19.

Clinical performance comparison of two medium cut-off dialyzers

INTRODUCTION

Medium-cut-off (MCO) dialyzers may beneficially impact outcomes in patients on hemodialysis.

METHODS

In a randomized, controlled trial in maintenance hemodialysis patients, the new Nipro ELISIO-17HX MCO dialyzer was compared to the Baxter Theranova 400 filter regarding middle molecule removal. Furthermore, the suitability of two assays for free lambda-light chain (λFLC) detection (Freelite vs. N-Latex) was verified.

RESULTS

ELISIO-HX achieved slightly lower reduction ratios for β₂ -microglobulin (71.8 ± 6.0 vs. 75.3 ± 5.8%; p = 0.001), myoglobin (54.7 ± 8.6 vs. 64.9 ± 8.7%; p < 0.001), and kappa-FLC (62.1 ± 8.8 vs. 56.3 ± 7.7%; p = 0.021). λFLC reduction ratios were more conclusive with the Freelite assay and not different between ELISIO-HX and Theranova (28.4 ± 3.9 vs. 38.7 ± 13.4%; p = 0.069). The albumin loss of Theranova was considerably higher (2.14 ± 0.45 vs. 0.77 ± 0.25 g; p = 0.001) and the Global Removal Score_{Loss alb} largely inferior (30.6 ± 7.4 vs. 82.4 ± 29.2%/g; p = 0.006) to ELISIO-HX.

CONCLUSIONS

The new ELISIO-HX expands the choice of dialyzers for MCO hemodialysis.

Hemodiafiltration: Technical and Medical Insights

Despite the significant medical and technical improvements in the field of dialytic renal replacement modalities, morbidity and mortality are excessively high among patients with end-stage kidney disease, and most interventional studies yielded disappointing results. Hemodiafiltration, a dialysis method that was implemented in clinics many years ago and that combines the two main principles of hemodialysis and hemofiltration-diffusion and convection-has had a positive impact on mortality rates, especially when delivered in a high-volume mode as a surrogate for a high convective dose. The achievement of high substitution volumes during dialysis treatments does not only depend on patient characteristics but also on the dialyzer (membrane) and the adequately equipped hemodiafiltration machine. The present review article summarizes the technical aspects of online hemodiafiltration and discusses present and ongoing clinical studies with regards to hard clinical and patient-reported outcomes.

Expanded hemodialysis: a new concept of renal replacement therapy

Expanded hemodialysis (HDx) is an innovation that can increase the effectiveness of hemodialysis. The dialysis process is expected to promote more uremic toxins removal without causing significant hypoalbuminemia using the medium cut-off (MCO) membrane or also known as the high retention onset membrane. Compared with conventional membranes such as those of low-flux hemodialysis, high-flux hemodialysis, and hemodiafiltration, the MCO membrane in HDx is considered to be the closest to the physiology of the glomerular membrane. Several studies have shown the use of the MCO membrane in HDx provides clinical benefits and better outcome although further studies are needed to assess the long-term effect and greater impact for dialysis patients.

The use of medium cutoff dialyzers in patients with multiple myeloma and acute kidney injury requiring hemodialysis: A systematic review

BACKGROUND

Patients with multiple myeloma and high serum levels of circulating free light chains (FLC) have increased risk of acute kidney injury (AKI) secondary to cast nephropathy and is associated with poor survival. Despite removal of FLC by medium cutoff (MCO) dialyzer, the role of MCO hemodialysis (HD) in the treatment of cast nephropathy and its clinical benefits remain unknown.

METHODS

A systematic review was conducted to establish the effectiveness of MCO dialyzer and clinical outcomes, compared to other forms of dialyzers in the removal of FLC, in myeloma patients with AKI. The primary outcome was effectiveness of MCO-HD in reducing serum FLC. The secondary outcomes were HD independence, estimated glomerular filtrate rate, mortality rates, length of hospitalization, rebound of serum FLC before the next dialysis, removal of other molecules during dialysis, and adverse events.

RESULTS

We identified three case series, with a total of 17 patients. There were no randomized controlled trials (RCTs) or cohort studies. These case series showed that MCO dialyzer was effective in the removal of FLC and led to a reduction in FLC concentration post-dialysis. The majority of the case series did not have comparator arm and renal and/or other clinical outcomes.

CONCLUSION

MCO dialyzer appeared to be effective in the removal of FLC based on the existing limited data. However, more data, particularly large-scale RCTs, are needed to assess the use of MCO dialyzer in reducing serum FLC and its effect on clinical outcomes in patients with multiple myeloma and AKI.

Efficacy and Safety of the Medium Cut-Off Elisio HX Dialyzer

INTRODUCTION

The medium cut-off Elisio HX dialyzer by Nipro became commercially available in Europe in 2021, but there are still no reports of in vivo data. This study aimed to evaluate the safety and efficacy of it compared with previously evaluated hemodialysis (HD), expanded HD (HDx), and postdilution hemodiafiltration (HDF) treatments.

METHODS

A prospective study was carried out on 18 patients who underwent 5 dialysis sessions: FX80 Cordiax in HD, Elisio H19 in HD, Elisio HX19 in HDx, Theranova 400 in HDx, and FX80 Cordiax in HDF. The reduction ratios of urea, creatinine, ß2-microglobulin, myoglobin, kappa FLC, prolactin, α1-microglobulin, α1-acid glycoprotein, lambda FLC, and albumin were compared. Dialysate albumin loss was measured.

RESULTS

The comparison between the different dialysis modalities revealed no difference for small molecules, but HDx and HDF were significantly more efficient than HD for medium and large molecule removal. The efficacy of Elisio HX19 dialyzer in HDx was similar to the Theranova 400, superior to both dialyzers in HD, and slightly lower than HDF. Albumin losses in dialysate with HD dialyzers were less than 1 g, but between 1.5 and 2.5 g in HDx and HDF. The global removal score (GRS) values with HDx treatments were statistically significantly higher than those with HD. The highest GRS was obtained with the helixone dialyzer in HDF.

CONCLUSIONS

The new MCO dialyzer, Elisio HX, performs with excellent behavior and tolerance. It represents an upgrade compared to their predecessor and is very close to the removal capacity of HDF treatment.

Comparison of four medium cut-off dialyzers

BACKGROUND

Recently, several pharmaceutical companies have developed new medium cut-off (MCO) dialyzers for expanded hemodialysis (HDx). This study aimed to compare the safety and efficacy of four MCO dialyzers, against each other and versus high-flux hemodialysis (HD) and post-dilution hemodiafiltration (HDF).

METHODS

A prospective study was carried out on 23 patients who underwent six dialysis sessions: two sessions with the FX80 Cordiax in HD and HDF, and four HDx sessions with the Phylther 17-SD, Vie-18X, Elisio HX19 and Theranova 400 dialyzers. The reduction ratios (RRs) of urea, creatinine, β2-microglobulin, myoglobin, kappa free immunoglobulin light chain (κFLC), prolactin, α1-microglobulin, α1-acid glycoprotein, lambda (λFLC) and albumin were compared. Dialysate albumin loss was also measured.

RESULTS

The differences in efficacy between the evaluated dialyzers were minimal in small molecules and even up to the size of β2-microglobulin. The main differences were found between myoglobin, κFLC, prolactin, α1-microglobulin and λFLC RRs, in which all four MCO dialyzers, with similar efficacy, were clearly superior to HD and slightly inferior to HDF treatment. Albumin losses in the dialysate with HD dialyzers were <1 g and between 1.5 and 2.5 g in HDx and HDF. The global removal score values were similar in all four HDx treatments, and again significantly higher than those with HD.

CONCLUSIONS

The results of the four MCO dialyzers evaluated in this study showed good efficiency, with no significant performance differences between them while being completely safe in terms of albumin loss. Likewise, the study confirms the superiority of HDx over high-flux HD with an efficacy close to that of post-dilution HDF.

Open Pore Ultrafiltration Hollow Fiber Membrane Fabrication Method via Dual Pore Former with Dual Dope Solution Phase

Hollow-fiber membranes are widely used in various fields of membrane processes because of their numerous properties, e.g., large surface area, high packing density, mass production with uniform quality, obvious end-of-life indicators, and so on. However, it is difficult to control the pores and internal properties of hollow-fiber membranes due to their inherent structure: a hollow inside surrounded by a wall membrane. Herein, we aimed to control pores and the internal structure of hollow-fiber membranes by fabricating a dual layer using a dual nozzle. Two different pore formers, polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP), were separately prepared in the dope solutions and used for spinning the dual layer. Our results show that nanoscale pores could be formed on the lumen side (26.8-33.2 nm), and the open pores continuously increased in size toward the shell side. Due to robust pore structure, our fabricated membrane exhibited a remarkable water permeability of 296.2 ± 5.7 L/m²·h·bar and an extremely low BSA loss rate of 0.06 ± 0.02%, i.e., a high BSA retention of 99.94%. In consideration of these properties, the studied membranes are well-suited for use in either water treatment or hemodialysis. Overall, our membranes could be considered for the latter application with a high urea clearance of 257.6 mL/min, which is comparable with commercial membranes.

A randomized prospective cross over study on the effects of medium cut-off membranes on T cellular and serologic immune phenotypes in hemodialysis

Extended cut-off filtration by medium cut-off membranes (MCO) has been shown to be safe in maintenance hemodialysis (HD). The notion of using them for the control of chronic low-grade inflammation and positively influencing cellular immune aberrations seems tempting. We conducted an open label, multicenter, randomized, 90 day 2-phase cross over clinical trial (MCO- vs. high flux-HD). 46 patients underwent randomization of which 34 completed the study. Dialysate- or pre- and post-dialysis serum inflammatory mediators were assayed for each study visit. Ex vivo T cell activation was assessed from cryopreserved leucocytes by flow cytometry. Linear mixed models were used to compare treatment modalities, with difference in pre-dialysis serum MCP-1 levels after 3 months as the predefined primary endpoint. Filtration/dialysate concentrations of most mediators, including MCP-1 (mean ± SD: 10.5 ± 5.9 vs. 5.1 ± 3.8 pg/ml, P < 0.001) were significantly increased during MCO- versus high flux-HD. However, except for the largest mediator studied, i.e., YKL-40, this did not confer any advantages for single session elimination kinetics (post-HD mean ± SD: 360 ± 334 vs. 564 ± 422 pg/ml, P < 0.001). No sustained reduction of any of the studied mediators was found neither. Still, the long-term reduction of CD69+ (P = 0.01) and PD1+ (P = 0.02) activated CD4+ T cells was striking. Thus, MCO-HD does not induce reduction of a broad range of inflammatory mediators studied here. Long-term reduction over a 3-month period was not possible. Increased single session filtration, as evidenced by increased dialysate concentrations of inflammatory mediators during MCO-HD, might eventually be compensated for by compartment redistribution or increased production during dialysis session. Nevertheless, lasting effects on the T-cell phenotype were seen, which deserves further investigation.

Impact of Hydrophilic Modification of Synthetic Dialysis Membranes on Hemocompatibility and Performance

The dialyzer is the core element in the hemodialysis treatment of patients with end-stage kidney disease (ESKD). During hemodialysis treatment, the dialyzer replaces the function of the kidney by removing small and middle-molecular weight uremic toxins, while retaining essential proteins. Meanwhile, a dialyzer should have the best possible hemocompatibility profile as the perpetuated contact of blood with artificial surfaces triggers complement activation, coagulation and immune cell activation, and even low-level activation repeated chronically over years may lead to undesired effects. During hemodialysis, the adsorption of plasma proteins to the dialyzer membrane leads to a formation of a secondary membrane, which can compromise both the uremic toxin removal and hemocompatibility of the dialyzer. Hydrophilic modifications of novel dialysis membranes have been shown to reduce protein adsorption, leading to better hemocompatibility profile and performance stability during dialysis treatments. This review article focuses on the importance of performance and hemocompatibility of dialysis membranes for the treatment of dialysis patients and summarizes recent studies on the impact of protein adsorption and hydrophilic modifications of membranes on these two core elements of a dialyzer.

Effect of Membrane Surface Area on Solute Removal Performance of Dialyzers with Fouling

In a clinical situation, since membrane fouling often causes the reduction of solute removal performance of the dialyzer, it is necessary to evaluate the performance of the dialyzer, considering the effects of fouling even in aqueous in vitro experiments that are useful for the better design of dialyzers. We replicated the membrane fouling by immobilizing albumin on the membrane in a dialyzer using glutaraldehyde as a stabilizer. The modules of various membrane surface areas with and without replication of the fouling were used for performance evaluation of solute (creatinine, vitamin B12, and inulin) removal in dialysis experiments in vitro. Clearances for these solutes in the modules with fouling were lower than those without fouling. Furthermore, the smaller the surface area, the larger the fouling effect was observed in all solutes. Calculated pressure distribution in a module by using a mathematical model showed that the solute removal performance might be greatly affected by the rate of internal filtration that enhances the solute removal, especially for larger solutes. The increase in the rate of internal filtration should contribute to improving the solute removal performance of the dialyzer, with a higher effect in modules with a larger membrane surface area.

Semi-Quantitative Evaluation of Asymmetricity of Dialysis Membrane Using Forward and Backward Ultrafiltration

Performance of the dialysis membrane is strongly dependent upon the physicochemical structure of the membrane. The objective of this study is to devise a new in vitro evaluation technique to quantify the physicochemical structures of the membrane. Three commercial dialyzers with cellulose triacetate (CTA), asymmetric CTA (termed ATA^®), and polyether sulfone (PES) membranes (Nipro Co., Osaka, Japan) were employed for investigation. Forward and backward ultrafiltration experiments were performed separately with aqueous vitamin B₁₂ (MW 1355), α-chymotrypsin (MW 25,000), albumin (MW 66,000) and dextran solutions, introducing the test solution inside or outside the hollow fiber (HF), respectively. Sieving coefficients (s.c.) for these solutes were measured under the test solution flow rate of 200 mL/min and the ultrafiltration rate of 10 mL/min at 310 K, according to the guidelines provided by Japanese academic societies. We defined the ratio of s.c. in the backward ultrafiltration to that in the forward ultrafiltration and termed it the index for asymmetricity (IA). The IA values were unity for vitamin B₁₂ and α-chymotrypsin in all three of the dialyzers. The IA values for albumin, however, were 1.0 in CTA, 1.9 in ATA^®, and 3.9 in PES membranes, respectively, which corresponded well with the fact that CTA is homogeneous, whereas ATA^® and PES are asymmetrical in structure. Moreover, the asymmetricity of ATA^® and PES may be different by twofold. This fact was verified in continuous basis by employing dextran solution before and after being fouled with albumin. These findings may contribute to the development of a novel membrane for improved success of dialysis therapy.

Impact of medium cut-off membranes on S100A12 and soluble receptor for advanced glycation end products

INTRODUCTION

Of the most remarkable molecules associated with atherosclerosis and the cardiovascular outcome are S100A12 (10,379.5 Da) and soluble receptor for advanced glycation end products (sRAGE-42,803 Da) in the hemodialysis (HD) population. We designed a study investigating the effects of the medium cut-off (MCO) dialyzers focusing on S100A12 and sRAGE in HD patients compared with low-flux and high-flux dialyzers.

METHODS

This single-site, prospective, observational study comprises age and sex-matched HD groups (low-flux, high-flux, and MCO). Blood samples were drawn at baseline (predialysis and postdialysis) and the sixth month (predialysis).

RESULTS

Groups had similar demographic features and laboratory parameters. Baseline S100A12 levels of the groups were similar [34.3 (±66.5), 30.9 (±42.7), and 40.6 (±29.6); p = 0.13]. Compared to their baseline, the sixth-month S100A12 levels were constant in low-flux and high-flux group and significantly lower in MCO group (p = 0.16, p = 0.33, and p = 0.004). Baseline sRAGE levels of the groups were similar at baseline [2.8 (±0.8), 2.7 (±0.6), and 2.6 (±0.7); p = 0.65], and the sixth-month [2.9 (±0.5), 2.4 (±0.7), and 2.4 (±0.8); p = 0.24]. sRAGE levels remained constant in all groups [p = 0.84, p = 0.13, and p = 0.39]. S100A12/sRAGE ratio at baseline and sixth month was constant in low-flux [22.3 (±63.7) and 18.1 (±24.8); p = 0.17] and high-flux groups [11.9 (±15.3) and 13.1 (±5.8); p = 0.26], the ratio decreased significantly in MCO group [16.5 (±11.6) to 7.8 (±5.5); p = 0.03].

CONCLUSION

Our study suggests that prolonged use of MCO dialyzers is associated with better S100A12 and sRAGE levels. Long-term studies with larger samples are needed to understand the effects of a better S100A12-sRAGE profile provided by MCO dialyzers on HD patients' cardiovascular outcomes.

Effects of Medium Cut-Off Polyarylethersulfone and Polyvinylpyrrolidone Blend Membrane Dialyzers in Hemodialysis Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The use of medium cut-off (MCO) polyarylethersulfone and polyvinylpyrrolidone blend membrane is an emerging mode in hemodialysis. Recent studies have shown that MCO membranes exhibit a middle high molecular weight uremic toxin clearance superior to standard high flux hemodialysis. We conducted a systematic literature review and meta-analysis of randomized controlled trials to investigate whether MCO membranes efficiently increase the reduction ratio of middle molecules, and to explore the potential clinical applications of MCO membranes. We selected articles that compared beta 2-microglobulin (β2M), kappa free light chain (κFLC), lambda free light chain (λFLC), interleukin-6 (IL-6), and albumin levels among patients undergoing hemodialysis. Five randomized studies with 328 patients were included. The meta-analysis demonstrated a significantly higher reduction ratio of serum β2M (p < 0.0001), κFLC (p < 0.0001), and λFLC (p = 0.02) in the MCO group. No significant difference was found in serum IL-6 levels after hemodialysis. Albumin loss was observed in the MCO group (p = 0.04). In conclusion, this meta-analysis study demonstrated the MCO membranes’ superior ability to clear β2M, κFLC, and λFLC. Serum albumin loss is an issue and should be monitored. Further studies are expected to identify whether MCO membranes could significantly improve clinical outcomes and overall survival.

Hemodiafiltration (HDF) versus expanded hemodialysis (HDx)

Medium cutoff (MCO) membranes have resulted in a novel dialyzer class designed to improve membrane permeability and have been postulated as an alternative to online hemodiafiltration since MCO membranes may achieve similar solute clearances. These membranes have been incorporated into clinical practice, and the term expanded HD (HDx) has been proposed to differentiate from high-flux hemodialysis. Efficacy, safety, and quality of life comparison of HDF versus HDx have been reviewed in this article.

Mass Transport in High-Flux Hemodialysis: Application of Engineering Principles to Clinical Prescription

An understanding of the processes underlying mass transfer is paramount for the attainment of adequate solute removal in the dialytic treatment of patients with kidney failure. In this review, engineering principles are applied to characterize the physical mechanisms behind the two major modes of mass transfer during hemodialysis, namely diffusion and convection. The manner in which flow rate, dialyzer geometry, and membrane microstructure affect these processes is discussed, with concepts such as boundary layers, effective membrane diffusivity, and sieving coefficients highlighted as critical considerations. The objective is to improve clinicians' understanding of these concepts as important factors influencing the prescription and delivery of hemodialysis therapy.

Effects of Expanded Hemodialysis with Medium Cut-Off Membranes on Maintenance Hemodialysis Patients: A Review

Kidney failure is associated with high morbidity and mortality. Hemodialysis, the most prevalent modality of renal replacement therapy, uses the principle of semipermeable membranes to remove solutes and water in the plasma of patients with kidney failure. With the evolution of hemodialysis technology over the last half century, the clearance of small water-soluble molecules in such patients is adequate. However, middle molecules uremic toxins are still retained in the plasma and cause cardiovascular events, anemia, and malnutrition, which significantly contribute to poor quality of life and high mortality in maintenance hemodialysis patients. A new class of membrane, defined as a medium cut-off (MCO) membrane, has emerged in recent years. Expanded hemodialysis with MCO membranes is now recognized as the artificial kidney model closest to natural kidney physiology. This review summarizes the unique morphological characteristics and internal filtration–backfiltration mechanism of MCO membranes, and describes their effects on removing uremic toxins, alleviating inflammation and cardiovascular risk, and improving quality of life in maintenance hemodialysis patients.

Lesión renal aguda en COVID-19: puesta al día y revisión de la literatura

Los coronavirus humanos son virus que se asocian a varias patologías respiratorias como el síndrome respiratorio agudo severo y el síndrome respiratorio del Medio Oriente. Esto ha puesto a esta familia de virus en el centro de atención de la comunidad científica debido a la alta patogenicidad en humanos, especialmente ahora con la nueva pandemia por la enfermedad por coronavirus del 2019 (COVID-19). La COVID-19 se manifiesta principalmente como enfermedad respiratoria aguda con compromiso respiratorio bajo, pero puede afectar múltiples órganos como lo es el riñón, lo cual a conlleva a peores desenlaces. En este manuscrito revisaremos el compromiso renal por los diferentes coronavirus, en especial en la COVID-19, al igual que las terapias que juegan algún papel en el tratamiento de esta.

Classification of Uremic Toxins and Their Role in Kidney Failure

Advances in our understanding of uremic retention solutes, and improvements in hemodialysis membranes and other techniques designed to remove uremic retention solutes, offer opportunities to readdress the definition and classification of uremic toxins. A consensus conference was held to develop recommendations for an updated definition and classification scheme on the basis of a holistic approach that incorporates physicochemical characteristics and dialytic removal patterns of uremic retention solutes and their linkage to clinical symptoms and outcomes. The major focus is on the removal of uremic retention solutes by hemodialysis. The identification of representative biomarkers for different classes of uremic retention solutes and their correlation to clinical symptoms and outcomes may facilitate personalized and targeted dialysis prescriptions to improve quality of life, morbidity, and mortality. Recommendations for areas of future research were also formulated, aimed at improving understanding of uremic solutes and improving outcomes in patients with CKD.

Effects of Medium Cutoff Membranes on Pro-Inflammatory Cytokine and Oxidative Marker Levels in Patients with Sepsis Who Developed Acute Kidney Injury

INTRODUCTION

There is insufficient data on the role of the medium cutoff (MCO) membranes in the clearance of pro-inflammatory cytokines and oxidant radicals in patients with sepsis requiring hemodialysis.

METHODS

The study consisted of 38 septic patients who developed acute kidney injury (AKI) and who were scheduled to undergo 2 sessions of hemodialysis. Nineteen patients underwent their first dialysis session with the MCO membrane and 19 patients with the high-flux (HF) membrane. In the second session, the membranes were switched. Pro-inflammatory cytokine and oxidative marker levels were measured in blood samples obtained before and after both dialysis sessions. Reduction ratios were compared for the 2 types of hemodialysis membranes.

RESULTS

After the first session, there was a greater reduction in tumor necrosis factor (TNF)-α with the MCO membrane (28.2 ± 21.1 vs. 8.0 ± 6.6, p = 0.001). After the second session, there was a greater reduction in interleukin (IL)-6 (27.8 ± 26.5 vs. 5.9 ± 13.3, p = 0.003) and IL-1β (20.5 ± 21.1 vs. 4.0 ± 6.5, p = 0.004) with the MCO membrane. When the first and second sessions of all 38 patients were compared, the reductions in TNF-α, IL-6, and IL-1β were consistently greater for MCO than HF (p = 0.001, p = 0.006, p < 0.001, respectively). The reductions in total antioxidant status, total oxidant status, and myeloperoxidase were not statistically different for the 2 types of dialysis membranes.

CONCLUSIONS

MCO membrane was superior to HF membrane in the removal of cytokines in septic patients with AKI. However, a similar effect was not observed for oxidative stress markers.

Recent advances in dialysis membranes

PURPOSE OF REVIEW

Improvement in hemodialysis treatment and membrane technology are focused on two aims: the first one is to achieve a better control of circulating uremic solutes by enhancing removal capacity and by broadening molecular weight spectrum of solutes cleared; the second one is to prevent inflammation by improving hemocompatibility of the global dialysis system.

RECENT FINDINGS

Despite impressive progresses in polymers chemistry few hazards are still remaining associated with leaching or sensitization to polymer additives. Research has focused on developing more stable polymers by means of additives or processes aiming to minimize such risks. Membrane engineering manufacturing with support of nanocontrolled spinning technology has opened up membrane to middle and large molecular weight substances, while preserving albumin losses. Combination of diffusive and enhanced convective fluxes in the same hemodialyzer module, namely hemodiafiltration, provides today the highest solute removal capacity over a broad spectrum of solutes.

SUMMARY

Dialysis membrane is a crucial component of the hemodialysis system to optimize solute removal efficacy and to minimize blood membrane biological reactions. Hemodialyzer is much more than a membrane. Dialysis membrane and hemodialyzer choice are parts of a treatment chain that should be operated in optimized conditions and adjusted to patient needs and tolerance, to improve patient outcomes.

Toward an individualized determination of dialysis adequacy: a narrative review with special emphasis on incremental hemodialysis

INTRODUCTION

The search for the 'perfect' renal replacement therapy has been paralleled by the search for the perfect biomarkers for assessing dialysis adequacy. Three main families of markers have been assessed: small molecules (prototype: urea); middle molecules (prototype β2-microglobulin); comprehensive and nutritional markers (prototype of the simplified assessment, albumin levels; composite indexes as malnutrition-inflammation score). After an era of standardization of dialysis treatment, personalized dialysis schedules are increasingly proposed, challenging the dogma of thrice-weekly hemodialysis.

AREAS COVERED

In this review, we describe the advantages and limitations of the approaches mentioned above, focusing on the open questions regarding personalized schedules and incremental hemodialysis.

EXPERT OPINION

In the era of personalized dialysis, the assessment of dialysis adequacy should be likewise personalized, due to the limits of 'one size fits all' approaches. We have tried to summarize some of the relevant issues regarding the determination of dialysis adequacy, attempting to adapt them to an elderly, highly comorbidity population, which would probably benefit from tailor-made dialysis prescriptions. While no single biomarker allows precisely tailoring the dialysis dose, we suggest using a combination of clinical and biological markers to prescribe dialysis according to comorbidity, life expectancy, residual kidney function, and small and medium-size molecule depuration.

Disruptive technologies for hemodialysis: medium and high cutoff membranes. Is the future now?

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.

Comparative analysis of therapeutic effects between medium cut-off and high flux dialyzers using metabolomics and proteomics: exploratory, prospective study in hemodialysis

In this single-center prospective study of 20 patients receiving maintenance hemodialysis (HD), we compared the therapeutic effects of medium cut-off (MCO) and high flux (HF) dialyzers using metabolomics and proteomics. A consecutive dialyzer membrane was used for 15-week study periods: 1st HF dialyzer, MCO dialyzer, 2nd HF dialyzer, for 5 weeks respectively. ¹H-nuclear magnetic resonance was used to identify the metabolites and liquid chromatography-tandem mass spectrometry (LC–MS/MS) analysis was used to identify proteins. To compare the effects of the HF and MCO dialyzers, orthogonal projection to latent structure discriminant analysis (OPLS-DA) was performed. OPLS-DA showed that metabolite characteristics could be significantly classified by 1st HF and MCO dialyzers. The Pre-HD metabolites with variable importance in projection scores ≥ 1.0 in both 1st HF versus MCO and MCO versus 2nd HF were succinate, glutamate, and histidine. The pre-HD levels of succinate and histidine were significantly lower, while those of glutamate were significantly higher in MCO period than in the HF period. OPLS-DA of the proteome also substantially separated 1st HF and MCO periods. Plasma pre-HD levels of fibronectin 1 were significantly higher, and those of complement component 4B and retinol-binding protein 4 were significantly lower in MCO than in the 1st HF period. Interestingly, as per Ingenuity Pathway Analysis, an increase in epithelial cell proliferation and a decrease in endothelial cell apoptosis occurred during the MCO period. Overall, our results suggest that the use of MCO dialyzers results in characteristic metabolomics and proteomics profiles during HD compared with HF dialyzers, which might be related to oxidative stress, insulin resistance, complement-coagulation axis, inflammation, and nutrition.

Expanded hemodialysis as effective alternative to on-line hemodiafiltration: A randomized mid-term clinical trial

Expanded hemodialysis (HDx), using medium cut-off membrane, is a novel therapy that effectively clears middle molecules (MMs). We aimed to compare HDx to hemodiafiltration (HDF) in an open randomized clinical study. Patients currently on HDF (age 18-80 years; on HDF >3 months) were randomized to switch to HDx (N = 21) or continue HDF (N = 22) with a 24-week follow-up. Pre- to post-dialysis reduction ratios (RR) and changes in pre-dialysis levels over time were evaluated for MMs and clinical biomarkers. Use of erythropoiesis-stimulating agents (ESAs) was assessed. HDx showed greater RR for YKL-40 while RR appeared similar between groups for beta₂ -microglobulin, FGF-23, and free light chains. Intradialytic changes in inflammatory biomarkers (IL-6, CRP, PTX3) did not differ between therapies. Changes from baseline to 12 and 24 weeks did not differ between groups for MMs, inflammatory markers, albumin, fibrinogen, hemoglobin, PTH, and phosphorus. Use of ESAs tended to decrease in HDx arm while remaining stable in HDF arm. HDx appeared safe with similar clinical effectiveness as HDF. With fewer requirements and resource needs, HDx provides an attractive alternative to HDF.

High-performance dialyzers and mortality in maintenance hemodialysis patients

Few data are available regarding the association of dialyzer type with prognosis. In Japan, dialyzers are classified as types I, II, III, IV, and V based on β₂-microglobulin clearance rates of < 10, < 30, < 50, < 70, and ≥ 70 mL/min, respectively. We investigated the relationship of the 5 dialyzer types with 1-year mortality. This nationwide cohort study used data collected at the end of 2008 and 2009 by the Japanese Society for Dialysis Therapy Renal Data Registry. We enrolled 203,008 patients on maintenance hemodialysis who underwent hemodialysis for at least 1 year and were managed with any of the 5 dialyzer types. To evaluate the association of dialyzer type with 1-year all-cause mortality, Cox proportional hazards models and propensity score-matched analyses were performed. After adjustment of the data with clinicodemographic factors, the type I, II, and III groups showed significantly higher hazard ratios (HRs) than the type IV dialyzers (reference). After adjustment for Kt/V and β₂-microglobulin levels, the HRs were significantly higher in the type I and II groups. After further adjustment for nutrition- and inflammation-related factors, the HRs were not significantly different between the type IV and type I and II groups. However, type V dialyzers consistently showed a significantly lower HR. With propensity score matching, the HR for the type V dialyzer group was significantly lower than that for the type IV dialyzer group. Additional long-term trials are required to determine whether type V dialyzers, which are high-performance dialyzers, can improve prognosis.

Cardiovascular Risk Comparison between Expanded Hemodialysis Using Theranova and Online Hemodiafiltration (CARTOON): A Multicenter Randomized Controlled Trial

Expanded hemodialysis (HDx) with medium cutoff (MCO) membranes, which remove middle-to-large molecules well, may be a good option to replace online hemodiafiltration (online-HDF). To provide more evidence, this randomized controlled trial compared several cardiovascular parameters between patients undergoing HDx and online-HDF. Eighty patients undergoing thrice-weekly hemodialysis were randomly assigned to receive either HDx with a Theranova membrane (n = 43) or online-HDF (n = 37). The primary endpoints were changes in brachial-ankle pulse wave velocity (baPWV), echocardiographic parameters, and coronary artery calcium (CAC) scores over 1 year, and the secondary endpoints included blood cardiovascular biomarkers, mortality, and patient-reported outcomes. A linear mixed model and log-rank test were used to estimate the group differences. 65 patients had completed the trial. The changes in baPWV and echocardiographic parameters did not differ between the two groups. The CAC scores remained stable in the online-HDF group, whereas an increasing trend was shown in the HDx group (P = 0.012). Other endpoints, including cardiovascular and all-cause mortalities, were similar between the two groups. The changes in cardiovascular parameters did not differ between HDx with an MCO membrane and online-HDF. However, attention may be needed in patients with high CAC scores or scores with an increasing tendency when online-HDF is replaced with HDx with an MCO membrane.

Effect of a medium cut-off dialyzer on protein-bound uremic toxins and mineral metabolism markers in patients on hemodialysis

INTRODUCTION

Hemodialysis (HD) with medium cut-off (MCO) dialyzers may expand molecular clearance, predominantly larger middle molecules (molecular weight 25-60 kDa). However, the impact of MCO dialyzers on long-term clearance of various other components of the uremic milieu is unknown. The tRial Evaluating Mid cut-Off Value membrane clearance of Albumin and Light chains in HemoDialysis patients (REMOVAL-HD) provided an opportunity to assess the effect of MCO dialyzers on protein-bound uremic toxins and novel markers of mineral metabolism.

METHODS

This exploratory sub-study of REMOVAL-HD evaluated changes in protein-bound solutes (total and free indoxyl sulfate [IS] and p-cresyl sulfate [PCS]) and mineral metabolism markers (intact fibroblast growth factor-23 [iFGF23], fetuin-A and endogenous calciprotein particles [CPP-1 and CPP-2]). Mid-week, pre-HD serum samples were collected at baseline and after 12 and 24 weeks of MCO use in stable adult patients. Change from baseline to Week 12 and 24 was estimated using linear mixed effects models.

FINDINGS

Eighty-nine participants were studied (mean age 67 ± 15 years, 38% female, 51% diabetic, median urine output 200 ml/24 h). Serum iFGF23 was reduced at Week 12 compared to baseline (-26.8% [95%CI -39.7, -11.1], p = 0.001), which was sustained at Week 24 (-21.7% [95%CI -35.7, -4.5], p = 0.012). There was no significant change in serum IS, PCS, fetuin-A, CPP-1, or CPP-2.

DISCUSSION

The use of a MCO dialyzer over 24 weeks was associated with a sustained reduction in FGF23, while other measured components of the uremic milieu were not significantly altered. Further studies are required to determine whether FGF23 reduction is associated with improved patient outcomes.

Continuous renal replacement therapy and extended indications

Extracorporeal blood purification (EBP) techniques provide support for critically ill patients with single or multiple organ dysfunction. Continuous renal replacement therapy (CRRT) is the modality of choice for kidney support for those patients and orchestrates the interactions between the different artificial organ support systems. Intensive care teams should be familiar with the concept of sequential extracorporeal therapy and plan on how to incorporate new treatment modalities into their daily practices. Importantly, scientific evidence should guide the decision-making process at the bedside and provide robust arguments to justify the costs of implementing new EBP treatments. In this narrative review, we explore the extended indications for CRRT as an adjunctive treatment to provide support for the heart, lung, liver, and immune system. We detail practicalities on how to run the treatments and how to tackle the most frequent complications regarding each of the therapies, whether applied alone or integrated. The physicochemical processes and technologies involved at the molecular level encompassing the interactions between the molecules, membranes, and resins are spotlighted. A clinical case will illustrate the timing for the initiation, maintenance, and discontinuation of EBP techniques.

Medium Cut-Off Membrane Can Be a New Treatment Tool in Amanita phalloides Poisoning

Mushroom poisoning is a common health problem that can be seen seasonally and geographically. Most mushroom poisoning requiring treatment worldwide is due to Amanita phalloides. Although liver failure and kidney injury are frequent, poisoning can also lead to more serious clinical situations, such as shock, pancreatitis, encephalopathic coma, cardiac failure, disseminated intravascular coagulation, and multiple organ dysfunction syndrome, and may cause death. In addition, when standard treatment approaches fail, extracorporeal treatment methods are often used. We report 2 cases in which hemodialysis with medium cut-off membrane was performed. We observed an improvement in liver and kidney function in both of our cases. The first case recovered, but the second case proved fatal owing to Acinetobacter sepsis, despite an improvement in renal function. Medium cut-off membrane hemodialysis may be an alternative option in the treatment of Amanita phalloides poisoning.

Updates on hemodialysis techniques with a common denominator: The personalization of the dialytic therapy

Hemodialysis (HD) is a life-saving therapy for patients with end-stage renal disease. In dialyzed patients, the prevalence of multi-morbidity is rising driven by various factors, such as the population aging, the incomplete correction of uremia, and the side effects of the dialysis therapy itself. Each dialyzed patient has their own specific clinical and biochemical problems. It is therefore unthinkable that the same dialysis procedure can be able to meet the needs of every patient on chronic dialysis. We have very sophisticated dialysis machines and different dialysis techniques and procedures beyond conventional HD, such as hemodiafiltration (HDF) with pre- and post-dilution, acetate-free biofiltration (AFB), hemofiltration (HF), and expanded HD. Each of these techniques has its own specific characteristics. To solve some intradialytic clinical issues, such as arterial hypotension and arrhythmias, we have biofeedback systems with automatic regulation of the blood volume, body temperature, arterial pressure, as well as potassium profiling techniques in the dialysis bath. New technical innovations, such as citrate-containing dialysate or heparin-coated membranes, could reduce the risk of bleeding. To better address to patient needs, the strengths and weaknesses of each of these systems must be well-known, in order to have a personalized dialysis prescription for each patient.

High cut-off dialysis mitigates pro-calcific effects of plasma on vascular progenitor cells

Mortality of patients with end-stage renal disease tremendously exceeds that of the general population due to excess cardiovascular morbidity. Large middle-sized molecules (LMM) including pro-inflammatory cytokines are major drivers of uremic cardiovascular toxicity and cannot be removed sufficiently by conventional high-flux (HFL) hemodialysis. We tested the ability of plasma from 19 hemodialysis patients participating in a trial comparing HFL with high cut-off (HCO) membranes facilitating removal of LMM to induce calcification in mesenchymal stromal cells (MSC) functioning as vascular progenitors. HCO dialysis favorably changed plasma composition resulting in reduced pro-calcific activity. LMM were removed more effectively by HCO dialysis including FGF23, a typical LMM we found to promote osteoblastic differentiation of MSC. Protein-bound uremic retention solutes with known cardiovascular toxicity but not LMM inhibited proliferation of MSC without direct toxicity in screening experiments. We could not attribute the effect of HCO dialysis on MSC calcification to distinct mediators. However, we found evidence of sustained reduced inflammation that might parallel other anti-calcifying mechanisms such as altered generation of extracellular vesicles. Our findings imply protection of MSC from dysfunctional differentiation by novel dialysis techniques targeted at removal of LMM. HCO dialysis might preserve their physiologic role in vascular regeneration and improve outcomes in dialysis patients.

Impact of Medium Cut-Off Dialyzers on Patient-Reported Outcomes: COREXH Registry

INTRODUCTION

A new generation of hemodialysis (HD) membranes called medium cut-off (MCO) membranes possesses enhanced capacities for middle molecule clearance, which have been associated with adverse outcomes in this population. These improvements could potentially positively impact patient-reported outcomes (PROs).

OBJECTIVE

The objective of this study was to evaluate the impact of MCO membranes on PROs in a cohort of HD patients in Colombia.

METHODS

This was a prospective, multicenter, observational cohort study of 992 patients from 12 renal clinics in Colombia who were switched from high-flux HD to MCO therapy and observed for 12 months. Changes in Kidney Disease Quality of Life 36-Item Short Form Survey (KDQoL-SF36) domains, Dialysis Symptom Index (DSI), and restless legs syndrome (RLS) 12 months after switching to MCO membranes were compared with time on high-flux membranes. Repeated measures of ANOVA were used to evaluate changes in KDQoL-SF36 scores; severity scoring was used to assess DSI changes over time; Cochran's Q test was used to evaluate changes in frequency of diagnostic criteria of RLS.

RESULTS

During 12 months of follow-up, 3 of 5 KDQoL-SF36 domains improved compared with baseline: symptoms (p < 0.0001), effects of kidney disease (p < 0.0001), and burden of kidney disease (p < 0.001). The proportion of patients diagnosed with RLS significantly decreased from 22.1% at baseline to 10% at 12 months (p < 0.0001). No significant differences in the number of symptoms (DSI, p = 0.1) were observed, although their severity decreased (p = 0.009).

CONCLUSIONS

In conventional HD patients, the expanded clearance of large middle molecules with MCO-HD membranes was associated with higher health-related quality of life scores and a decrease in the prevalence of RLS.

Comparison of Hemodialysis Using a Medium Cutoff Dialyzer versus Hemodiafiltration: A Controlled Cross-Over Study

Purpose

Conventional hemodialysis (HD) treatment has an acceptable removal of small uremic molecules, but so-called "middle molecules" in the range of 0.5-60 kDa are poorly cleared with HD compared to a native kidney, which may contribute to morbidity in the dialysis population. Hemodiafiltration (HDF) has a better removal of middle molecules compared to HD but is technically demanding and requires well-functioning dialysis access. The newly introduced medium cutoff (MCO) filters have been developed to enhance middle molecule clearance in HD-mode. The aim of this study was to compare reduction ratios (RRs) of molecules with different molecular weights (0.06-150 kDa) during dialysis with MCO dialyzer (used in HD-mode) compared to online-hemodiafiltration (ol-HDF) treatment with a conventional high-flux dialyzer.

Patients and Methods

This is a prospective controlled single-center cross-over study, including 16 patients in Malmö, Sweden. All patients had ongoing post-dilution ol-HDF treatment before the study. The study compared reduction ratios of small-, middle-, and large-sized molecules during a single 4h dialysis treatment with post-dilution ol-HDF (Polyflux 210H) to a 4h dialysis treatment with MCO dialyzer (Theranova 500) in HD-mode. Between treatments, the patients had a washout period of at least two weeks of their ordinary HDF treatment to reach their ordinary steady state.

Results

ol-HDF had significantly higher RR for cystatin C (13 kDa), compared to MCO (RR 68.1 vs 65.8, p=0.003), during a 4h dialysis treatment (mean convection volume of 24.5 L for HDF, and mean Q_b of 324 mL/min for HDF and 323 mL/min for MCO). There was no significant difference in the RR for other middle molecules, or for smaller or larger molecules.

Conclusion

Overall, the RRs were comparable for ol-HDF and MCO-HD. There was a slightly higher RR of cystatin C (a small middle molecule) for HDF compared to MCO but no difference in other measured molecules.

Medium cut-off dialyzer improves erythropoiesis stimulating agent resistance in a hepcidin-independent manner in maintenance hemodialysis patients: results from a randomized controlled trial

The response to erythropoiesis stimulating agents (ESAs) is affected by inflammation linked to middle molecules in hemodialysis (HD) patients. We evaluated the effect of a medium cut-off (MCO) dialyzer on ESA resistance in maintenance HD patients. Forty-nine patients who underwent high-flux HD were randomly allocated to the MCO or high-flux group. The primary outcome was the changes of erythropoietin resistance index (ERI; U/kg/wk/g/dL) between baseline and 12 weeks. The MCO group showed significant decrease in the ESA dose, weight-adjusted ESA dose, and ERI compared to the high-flux group at 12 weeks (p < 0.05). The generalized estimating equation models revealed significant interactions between groups and time for the ESA dose, weight-adjusted ESA dose, and ERI (p < 0.05). Serum iron and transferrin saturation were higher in the MCO group at 12 weeks (p < 0.05). The MCO group showed a greater reduction in TNF-α and lower serum TNF-α level at 12 weeks compared to the high-flux group (p < 0.05), whereas no differences were found in the reduction ratio of hepcidin and serum levels of erythropoietin, erythroferrone, soluble transferrin receptor and hepcidin between groups. HD with MCO dialyzer improves ESA resistance over time compared to high-flux HD in maintenance HD patients. The MCO dialyzer provides superior removal of the inflammatory cytokine and thus improves iron metabolism in a hepcidin-independent manner.

Efficacy and Safety of Expanded Hemodialysis with the Theranova 400 Dialyzer: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Expanded hemodialysis therapy enabled by medium cut-off membranes may promote greater clearance of larger middle molecules that comprise putative uremic solutes than conventional high-flux dialysis. This randomized trial evaluated the efficacy and safety of hemodialysis treatment with a medium cut-off dialyzer.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Clinically stable patients on maintenance hemodialysis were randomized to receive dialysis with either a medium cut-off dialyzer (Theranova 400) or a high-flux dialyzer (Elisio-17H) over 24 weeks of treatment. The primary safety end point was the predialysis serum albumin level after 24 weeks of treatment. The primary efficacy end point was the reduction ratio of free λ light chains at 24 weeks of treatment.

RESULTS

Among 172 patients on maintenance hemodialysis, mean age was 59±13 years, 61% were men, 40% were Black, and mean dialysis vintage was 5±4 years. Of the 86 patients randomized to each dialyzer, 65 completed the trial in each group. The reduction ratio for the removal of free λ light chains was significantly higher in the Theranova 400 group compared with the Elisio-17H group after 4 weeks (39% versus 20%) and 24 weeks (33% versus 17%; both P<0.001). Among secondary end points, the Theranova 400 group demonstrated significantly larger reduction ratios at 4 and 24 weeks for complement factor D, free κ light chains, TNFα, and β2-microglobulin (P<0.001 for all), but not for IL-6. Predialysis serum albumin levels were similar between groups after 24 weeks (4 g/dl with the Theranova 400 and 4.1 g/dl with the Elisio-17H), consistent with noninferiority of the Theranova 400 dialyzer in maintaining predialysis serum albumin levels after 24 weeks of treatment.

CONCLUSIONS

Hemodialysis therapy with the Theranova 400 dialyzer provides superior removal of larger middle molecules, as exemplified by free λ light chains, compared with a similar size high-flux dialyzer, while maintaining serum albumin level.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

A Multi-Center, Prospective, Randomized, Controlled, Open-Label, Parallel Study to Evaluate the Safety and Efficacy of the Theranova 400 Dialyzer in End Stage Renal Disease (ESRD) Patients, NCT03257410.

Contrast-Enhanced Ultrasonography as a Novel Method for the Dynamic Visualization of Blood Flow and Fiber Blockage in Dialyzers: A Feasibility Study

The capillary dialyzer represents the central element of the extracorporeal blood circuit of a therapy system for hemodialysis. The aim of this study was to assess the blood-flow characteristics of dialyzers with the help of modern ultrasound techniques. Five brand-new dialyzers (FX80 classix, Fresenius Medical Care, Bad Homburg, Germany) and five dialyzers after a dialysis session were analyzed by different ultrasound techniques to detect functional and structural changes. B-mode and Doppler techniques were not suitable to describe differences in brand-new and clinically applied dialyzers. Contrast-enhanced ultrasonography, however, was able to visualize blood-flow profiles in the capillaries. Although dialyzers displayed no signs of clinical dysfunction, contrast-enhanced ultrasonography was able to detect blocked capillaries of varying degrees after a dialysis session in all five examined dialyzers. Consequently, the blood-flow velocity was higher in the remaining unblocked capillaries in comparison to the velocity in the brand-new dialyzers. This information may be helpful for improving the geometric design of dialyzers, including their capillary membranes, and optimizing anti-coagulation strategies in hemodialysis patients.

Efficacy of enoxaparin in preventing coagulation during high-flux haemodialysis, expanded haemodialysis and haemodiafiltration

Background

Low-molecular-weight heparins (LMWHs) are easily dialysable with high-flow membranes; however, it is not clear whether the LMWH dose should be adjusted according to the membrane type and dialysis technique. This study aimed to evaluate the influence of the dialyser on anticoagulation of the extracorporeal dialysis circuit.

Methods

Thirteen patients received the same dose of LMWH through the arterial port via three dialysis techniques: high-flux haemodialysis (HF-HD), online haemodiafiltration (HDF) and expanded haemodialysis (HDx). All dialysis was performed under similar conditions: duration, 4 h; blood flow, 400 mL/min; and dialysate flow, 500 mL/min. Antifactor Xa (aXa) activity and activated partial thromboplastin time (APTT) were measured before and after the dialysis. Clotting time of the vascular access site after haemodialysis, visual clotting score of the dialyser and any complications with the extracorporeal circuit or bleeding were registered.

Results

Post-dialysis aXa activity in HF-HD (0.26 ± 0.02 U/mL) was significantly different from that in HDF (0.21 ± 0.02 U/mL, P = 0.024), and there was a trend in HDx (0.22 ± 0.01 U/mL, P = 0.05). APTT post-dialysis in HF-HD (30.5 ± 0.7 s) was significantly different from that in HDx (28.2 ± 0.64 s, P = 0.009) and HDF (28.8 ± 0.73 s, P = 0.009).

Conclusions

AXa activity in HDF was significantly lower than that in HF-HD, possibly because of more losses of LMWH through the dialyser. Given the higher anticoagulant loss in HDF and probably in HDx than in HF-HD, the enoxaparin dose administered may be adjusted according to the dialysis technique.