Hemocompatibility of Polysulfone Hemodialyzers – Exploratory Studies on Impact of Treatment Modality and Dialyzer Characteristics

Preparation and Hemocompatibility of Novel Antioxidant-Modified Polyethersulfone Membranes as Red Blood Cell Thrombosis Inhibitors

The contact between the dialysis membrane and blood can induce oxidative stress and thrombosis, causing oxidative organ damage and impaired toxin clearance. To date, the selection of anticoagulants has focused on mechanisms inhibiting white, but not red (erythrocytes) thrombus formation. In the present study, polyethersulfone (PES) membranes are modified with the antioxidant drug tiopronin; the physicochemical properties and dialysis performance of the Tio-PES membranes are evaluated. The effects on erythrocyte thrombosis are evaluated in terms of erythrocyte morphology, prothrombotic properties (adhesion, aggregation, viscosity, sedimentation, and hemolysis), and fibrinogen (FIB)-erythrocyte interactions. The regular anticoagulant and antiplatelet properties are also assessed. Superoxide dismutase, malondialdehyde, plasma protein, and complement C3a are further determined. Finally, the biosafety of the Tio-PES membranes is evaluated both in vitro and in vivo. The Tio-PES membranes exhibit excellent physicochemical properties and improved dialysis performance. It is found that the Tio-PES membranes stabilize erythrocyte morphology, reduce erythrocyte prothrombotic properties, decrease FIB adsorption, and prevent red thrombus formation. In addition, the Tio-PES membranes exhibit excellent antioxidant properties and show biosafety in primary toxicity studies. Thus, Tio-PES membranes hold promise as novel, safe, and effective dialysis materials for potential clinical application.

Efficacy and Safety of Modified Polyethersulfone Hemodialysis Filters in Comparison to Conventional Filters: A Non-inferiority Clinical Trial

Background: The efficacy and quality of hemodialysis (HD) are closely related to the dialyzer characteristics. Objectives: This study aimed to determine the efficacy and complications of modified polyethersulfone (m-PES) -1.5 hollow fiber filters in comparison to conventional filters during HD. Methods: This non-inferiority crossover randomized clinical trial was performed in adult dialysis units at three HD centers within May 2019 to March 2020. The patients were randomly enrolled in two groups. Group A was first put on HD for six sessions with a low or high flux smart flux filter (m-PES-1.5 hollow fiber), which was made in Italy by Medica S.P.A. Group. Group B was hemodialyzed with a corresponding low or high flux filter made in Iran by Meditechsys Company. After a two-week clearance phase, the patients were dialyzed for six sessions with the opposite filter of the first six sessions. Laboratory variables, such as blood urea nitrogen and creatinine, were measured. Kt/V (i.e., a measurement of HD efficacy) and urea reduction ratio (URR) were calculated. Additionally, blood pressure was monitored. Results: A total of 40 patients were entered into the final analysis. No matter which filter was used, no statistically significant differences were observed in URR, creatinine, Kt/V, and blood pressure at different times during dialysis between the two types of filters. Packaging problems (P < 0.001) and blood clotting (P = 0.009) were two more frequent complications in the m-PES group. Conclusions: This study showed that smart flux m-PES-1.5 hollow fiber filters are similar to Meditechsys Company filters.

Effect of dialyzer geometry on coagulation activation in the extracorporeal circuit in maintenance hemodialysis patients: Prospective randomized trial

BACKGROUND AND OBJECTIVES

The coagulation cascade is activated during hemodialysis (HD) due to interaction of blood with the dialysis circuit. There is a paucity of data on the effect of the physical structure of the dialyzers on coagulation activation during HD. We conducted this study to compare the effect of Helixone FX80 versus Platinum H4 dialyzers on coagulation activation during HD.

METHODS

Twenty patients on maintenance HD were enrolled in this randomized prospective crossover study. Each patient was dialyzed using Helixone FX80 and Platinum H4 dialyzers. Serum thrombin-antithrombin complex (TAT) was measured before (T0h) and at the end (T4H) of HD.

RESULTS

The absolute changes of serum TAT were comparable with the two dialyzers (median [IQR]: 1.15 [0.65, 1.75] for Helixone FX80 vs. 1.15 [0.67, 2.05] for Platinum H4, p = 0.371).

CONCLUSION

Helixone FX80 and Platinum H4 dialyzers have similar effects on coagulation activation during HD.

Hidden risks associated with conventional short intermittent hemodialysis: A call for action to mitigate cardiovascular risk and morbidity

The development of maintenance hemodialysis (HD) for end stage kidney disease patients is a success story that continues to save many lives. Nevertheless, intermittent renal replacement therapy is also a source of recurrent stress for patients. Conventional thrice weekly short HD is an imperfect treatment that only partially corrects uremic abnormalities, increases cardiovascular risk, and exacerbates disease burden. Altering cycles of fluid loading associated with cardiac stretching (interdialytic phase) and then fluid unloading (intradialytic phase) likely contribute to cardiac and vascular damage. This unphysiologic treatment profile combined with cyclic disturbances including osmotic and electrolytic shifts may contribute to morbidity in dialysis patients and augment the health burden of treatment. As such, HD patients are exposed to multiple stressors including cardiocirculatory, inflammatory, biologic, hypoxemic, and nutritional. This cascade of events can be termed the dialysis stress storm and sickness syndrome. Mitigating cardiovascular risk and morbidity associated with conventional intermittent HD appears to be a priority for improving patient experience and reducing disease burden. In this in-depth review, we summarize the hidden effects of intermittent HD therapy, and call for action to improve delivered HD and develop treatment schedules that are better tolerated and associated with fewer adverse effects.

Randomized comparison of three high-flux dialyzers during high-volume online hemodiafiltration—the comPERFORM study

Background

Dialyzers should be designed to efficiently eliminate uraemic toxins during dialysis treatment, given that the accumulation of small and middle molecular weight uraemic solutes is associated with increased mortality risk of patients with end-stage renal disease. In the present study we investigated the novel FX CorAL dialyzer with a modified membrane surface for performance during online hemodiafiltration (HDF) in a clinical setting.

Methods

comPERFORM was a prospective, open, controlled, multicentric, interventional, crossover study with randomized treatment sequences. It randomized stable patients receiving regular post-dilution online HDF to FX CorAL 600 (Fresenius Medical Care Deutschland), xevonta Hi 15 (B. Braun) and ELISIO 150H (Nipro) each for 1 week. The primary outcome was β2-m removal rate (β2-m RR) during online HDF. Secondary endpoints were RR and/or clearance of β2-m and other molecules. Albumin removal over time was an exploratory endpoint. Non-inferiority and superiority of FX CorAL 600 versus comparators were tested.

Results

Fifty-two patients were included and analysed. FX CorAL 600 showed the highest β2-m RR (75.47%), followed by xevonta Hi 15 (74.01%) and ELISIO 150H (72.70%). Superiority to its comparators was statistically significant (P = 0.0216 and P < 0.0001, respectively). Secondary endpoints related to middle molecules affirmed these results. FX CorAL 600 demonstrated the lowest albumin removal up to 60 minutes and its sieving properties changed less over time than with comparators.

Conclusions

FX CorAL 600 efficiently removed middle and small molecules and was superior to the two comparators in β2-m RR. Albumin sieving kinetics point to reduced formation of a secondary membrane.

Hemodialysis-Related Complement and Contact Pathway Activation and Cardiovascular Risk: A Narrative Review

Individuals receiving long-term hemodialysis are at increased risk of developing cardiovascular disease (CVD). Traditional cardiovascular risk factors do not fully explain the high CVD risk in this population. During hemodialysis, blood interacts with the biomaterials of the hemodialysis circuit. This interaction can activate the complement system and the factor XII-driven contact system. FXII activation triggers both the intrinsic pathway of coagulation and the kallikrein-kinin pathway, resulting in thrombin and bradykinin production, respectively. The complement system plays a key role in the innate immune response, but also contributes to the pathogenesis of numerous disease states. Components of the complement pathway, including mannose binding lectin and C3, are associated with CVD risk in people with end-stage kidney disease (ESKD). Both the complement system and the factor XII-driven contact coagulation system mediate proinflammatory and procoagulant responses that could contribute to or accelerate CVD in hemodialysis recipents. This review summarizes what is already known about hemodialysis-mediated activation of the complement system and in particular the coagulation contact system, emphasizing the potential role these systems play in the identification of new biomarkers for CVD risk stratification and the development of potential therapeutic targets or innovative therapies that decrease CVD risk in ESKD patients.

Complement activation by dialysis membranes and its association with secondary membrane formation and surface charge

Activation of the complement system may occur during blood-membrane interactions in hemodialysis and contribute to chronic inflammation of patients with end-stage renal disease. Hydrophilic modification with polyvinylpyrrolidone (PVP) has been suggested to increase the biocompatibility profile of dialysis membranes. In the present study we compared the complement activation of synthetic and cellulose-based membranes, including the polysulfone membrane with α-tocopherol-stabilized PVP-enriched inner surface of the novel FX CorAL dialyzer, and linked the results to their physical characteristics. Eight synthetic and cellulose-based dialyzers (FX CorAL, FX CorDiax [Fresenius Medical Care]; Polyflux, THERANOVA [Baxter]; ELISIO, SUREFLUX [Nipro]; xevonta [B. Braun]; FDX [Nikkisio Medical]) were investigated in the present study. Complement activation (C3a, C5a, and sC5b-9) was evaluated in a 3 hours ex vivo recirculation model with human blood. Albumin sieving coefficients were determined over a 4 hours ex vivo recirculation model with human plasma as a surrogate of secondary membrane formation. Zeta potential was measured as an indicator for the surface charge of the membranes. The FX CorAL dialyzer induced the lowest activation of the three complement factors (C3a: -39.4%; C5a: -57.5%; and sC5b-9: -58.9% compared to the reference). Highest complement activation was found for the cellulose-based SUREFLUX (C3a: +154.0%) and the FDX (C5a: +335.0% and sC5b-9: +287.9%) dialyzers. Moreover, the FX CorAL dialyzer had the nearest-to-neutral zeta potential (-2.38 mV) and the lowest albumin sieving coefficient decrease over time. Albumin sieving coefficient decrease was associated with complement activation by the investigated dialyzers. Our present results indicate that the surface modification implemented in the FX CorAL dialyzer reduces the secondary membrane formation and improves the biocompatibility profile. Further clinical studies are needed to investigate whether these observations will result in a lower inflammatory burden of hemodialysis patients.