Rationale for Medium Cutoff Membranes in COVID-19 Patients Requiring Renal Replacement Therapy

Medium cut-off dialyzer for middle molecular uremic toxins in AKI and chronic dialysis

Uremic toxins accumulate in patients affected by renal failure and can deposit in different organs, including the kidneys and heart. Given their physicochemical characteristics, uremic toxins can contribute to organ dysfunction due to several pathobiological actions at cellular and molecular levels. Several uremic compounds have been described in serum and plasma from patients with acute kidney injury (AKI) and kidney failure; they are usually classified based on their molecular size and protein-binding properties. In this scenario, new dialytic approaches have been proposed in the last few years with the aim of improving uremic toxin removal. Recent studies which focused on the use of medium cut-off membranes in patients on chronic hemodialysis have shown a discrete ability to remove β2-microglobulin and other middle molecules, such as kappa and lambda free light chains, complement factor D and α1-microglobulin. However, current evidence is mainly based on the impact on short-term outcomes and, consequently, longer observational studies are necessary to confirm the efficacy and safety of the medium cut-off dialyzer. Here we present the state-of-the-art on the clinical application of medium cut-off membranes in AKI and chronic dialysis patients.

AKI in Adults with COVID-19 Infection: Mechanisms of Development and Role of Blood Filtration Devices in Treatment

During the coronavirus disease 2019 (COVID-19) pandemic, acute kidney injury (AKI) was a common sequela of COVID-19 infection and predicted disease severity and mortality. Extracorporeal blood purification techniques involving blood filtration devices are an emerging treatment for AKI in the setting of severe COVID-19 infections. In this review, we discuss potential mechanisms for the development of AKI in COVID-19 patients as well as the various available blood filtration devices and the role they may play in managing the AKI in COVID-19 patients. A total of seven blood filters currently available were compared based on their potential in treating AKI in COVID-19 patients. Blood filtration devices show potential as an emerging treatment modality for COVID-19-induced AKI, but further clinical trials are necessary before their widespread adoption and usage.

Arteriovenous fistula as the vascular access contributes to better survival of hemodialysis patients with COVID-19 infection

BACKGROUND

While COVID-19 in chronic hemodialysis patients has high mortality and the pandemic will not end in the near future, effective follow up strategies should be implemented for these patients. Surgeries have been triaged according to their level of urgencies and arteriovenous fistula (AVF) operations were among elective surgeries. This study aimed to analyze the effect of vascular access on the outcomes of hemodialysis patients who had COVID-19.

METHODS

One hundred four hemodialysis patients who had COVID-19 were retrospectively analyzed. Seventy-two of them had AVF as the vascular access while 32 of them had tunneled catheters. Inflammatory markers and outcomes of patients with AVFs and catheters were compared. A logistic regression analysis was performed in order to define factors that contribute to better outcomes in hemodialysis patients.

RESULTS

COVID-19 had high mortality rate in hemodialysis patients (36.5%). Patients with catheters have higher peak ferritin levels (p = 0.02) and longer hospital stay (p = 0.00). Having AVF as the vascular access (OR = 3.36; 95% CI: 1.05-10.72; p = 0.041) and using medium cut-off dialyzers (OR = 7.99; 95% CI: 1.53-41.65; p = 0.014) were related to higher survival of the patients. COVID severity was inversely proportional to the survival (p = 0.000).

CONCLUSIONS

AVFs contribute to higher survival of hemodialysis patients with COVID-19. Even in the pandemic era, end stage renal disease patients should be given the opportunity to have their vascular access properly created.

Anti-Inflammatory Approach in Chronic Dialysis Patients with SARS-CoV-2: ATA or PMMA Dialyzers?

INTRODUCTION

High-flux hemodialysis membranes may modulate the cytokine storm of SARS-CoV-2, but their impact on chronic hemodialysis (CHD) patients is unknown. The aim of the study was the evaluation of asymmetric cellulose triacetate (ATA) and polymethylmethacrylate (PMMA) dialyzers on inflammatory markers and clinical outcomes in CHD patients with SARS-CoV-2.

METHODS

A prospective, observational study on CHD patients with SARS-CoV-2 was carried out. Patients were enrolled from March 2020 to May 2021. Pre- and postdialysis C-reactive protein (CRP), procalcitonin (PCT), and interleukin-6 (IL-6) were determined at each session. Patients who underwent on-line hemodiafiltration (OLHDF) with a PMMA dialyzer were compared with those treated with OLHDF with a ATA dialyzer. The primary endpoint was the differences in the reduction ratio per session (RR) of CRP, PCT, IL-6, and IL-6 RR >25%.

RESULTS

We consecutively enrolled 74 CHD patients with COVID-19, 48 were treated with ATA membrane, and 26 with PMMA. Median IL-6 RR was higher in the ATA group compared to PMMA (17.08%, IQR -9.0 to 40.0 vs. 2.95%, IQR -34.63 to 27.32). Median CRP RR was 7.77% (IQR 2.47-13.77) in the ATA group versus 4.8% (IQR -2.65 to 11.38) in the PMMA group (p = 0.0017). Median PCT-RR% was 77.38% (IQR 70.92-82.97) in ATA group versus 54.59% (IQR 42.62-63.16) in the PMMA group (p < 0.0001). A multiple logistic regression analysis with IL-6 RR >25% as the outcome including the membrane employed, pre-dialysis IL-6, CRP, PCT, and ferritin showed that ATA led to a higher probability to reach the outcome (OR 1.891, 95% CI 1.273-2.840, p = 0.0018) while higher CRP favors the risk of lower IL-6 RR values (OR 0.910, 95% CI 0.868-0.949, p ≤ 0.0001).

CONCLUSIONS

In SARS-CoV-2 CHD patients treated with OLHDF, ATA showed a better anti-inflammatory profile, regarding IL-6 RR, compared to PMMA.

Fluctuations in Interleukin-6 Levels during Hemodialysis Sessions with Medium Cutoff Membranes: An Analysis on COVID-19 Case Series

INTRODUCTION

Interleukin-6 (IL-6) is one of the most important mediators of inflammation. It is also the culprit for a severe disease course in COVID-19. While COVID-19 has higher mortality in hemodialysis (HD) patients, medium cutoff (MCO) membranes were previously suggested as promising tools for better patient outcomes by purging inflammatory mediators. The aim of this study was to analyze changes in IL-6 levels of HD patients who were dialyzed via MCO membranes during their COVID-19 treatments.

METHODS

This is an observational study on a group of HD patients who were admitted with COVID-19 diagnosis in a university hospital and intermittently dialyzed using MCO membranes during their hospital stay. IL-6 levels of the patients were measured before and after consecutive dialysis sessions by a commercial kit. Measurements were interpreted together with the clinical data.

RESULTS

Nine patients with a total of 54 measurements were evaluated. IL-6 levels were significantly higher in patients who died (median and interquartile ranges [IQRs] of IL-6 levels for patients who died and survived were 112.0 pg/mL [48.3-399.4] and 5.3 pg/mL [2.2-27.4], respectively; p < 0.001). In the comparison of changes in IL-6 levels with dialysis sessions, patients who survived had lower post-dialysis levels (median: 4.5 pg/mL; IQR: 2.2-7.6). However, IL-6 levels had a tendency to increase with dialysis sessions in patients who could not survive COVID-19 (median: 237.0 pg/mL; IQR: 53.8-418.2).

CONCLUSION

This study describes over time variations in IL-6 levels of COVID-19 patients undergoing HD with MCO membranes. The trend for the changes of IL-6 levels during dialysis sessions was not uniform for all patients. Surviving patients had decreasing levels of IL-6 with consecutive dialysis sessions, while nonsurvivors had an increasing trend.

COVID-19 in Chronic Kidney Disease: The Impact of Old and Novel Cardiovascular Risk Factors

Cardiovascular disease is a frequent complication and the most common cause of death in patients with CKD. Despite landmark medical advancements, mortality due to cardiovascular disease is still 20 times higher in CKD patients than in the general population, which is mainly due to the high prevalence of risk factors in this group. Indeed, in addition to traditional cardiovascular risk factors, CKD patients are exposed to nontraditional ones, which include metabolic, hormonal, and inflammatory alterations. The global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has brought novel challenges for both cardiologists and nephrologists alike. Emerging evidence indicates that coronavirus disease 2019 (COVID-19) increases the risk of cardiovascular events and that several aspects of the disease may synergize with pre-existing cardiovascular risk factors in CKD patients. A better understanding of these mechanisms is pivotal for the prevention and treatment of cardiovascular events in this context, and we believe that additional clinical and experimental studies are needed to improve cardiovascular outcomes in CKD patients with COVID-19. In this review, we provide a summary of traditional and nontraditional cardiovascular risk factors in CKD patients, discussing their interaction with SARS-CoV-2 infection and focusing on CO-VID-19-related cardiovascular complications that may severely affect short- and long-term outcomes in this high-risk population.

Targeting Cytokine Storm in COVID-19: A Role of Online Hemodiafiltration with Asymmetric Cellulose Triacetate in Maintenance Hemodialysis Patients-A Report of 10 Cases

Early reports have suggested that maintenance hemodialysis (MHD) patients could be more susceptible to a severe course of COVID-19. Among the therapeutic approaches, the use of drugs that reduce the cytokine storm characteristic of this disease has been proposed. Some dialyzers, such as the new generation of asymmetric cellulose triacetate (ATA) membranes, could favor the effective elimination of medium-sized molecules and other inflammatory mediators. In this case series, we describe in depth the clinical, analytical, and radiological details, therapeutic aspects, and outcomes of the case series of 10 MHD patients of our dialysis unit, who tested positive for SARS-CoV-2 from 5 October to 30 November 2020. Furthermore, we evaluate the removal of hyperinflammatory parameters with the ATA membrane in postdilution online hemodiafiltration (OL-HDF) in these patients through a variety of biomarkers of systemic inflammation from the diagnosis until stripping. Biochemical blood analysis was carried out at baseline and at days 7 and 14 after diagnosis, respectively. 50% of the patients presented COVID-19 pneumonia and required hospital admission. Median hospitalization time was 21 days. A total of 4 patients developed severe pneumonia (3 of them died) and 1 patient developed moderate pneumonia. Patients who died (n = 3) were more likely to present bilateral pneumonia (100% vs 14.3%) at diagnosis and less reduction in interleukin 6 (IL-6) at day 14, as compared to those who survived. The use of the ATA membrane could be considered a therapeutic option, due to its immunomodulatory effect in MHD patients with SARS-CoV-2 infection, especially at the beginning of the disease, where the inflammatory component is predominant.

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.

Epidemiology and Outcomes of Acute Kidney Injury in COVID-19 Patients with Acute Respiratory Distress Syndrome: A Multicenter Retrospective Study

Background

Acute kidney injury (AKI) is associated with increased mortality in patients with acute respiratory distress syndrome (ARDS). However, the epidemiological features and outcomes of AKI among COVID-19 patients with ARDS are unknown.

Methods

We retrospectively recruited consecutive adult COVID-19 patients who were diagnosed with ARDS according to Berlin definition from 13 designated intensive care units in the city of Wuhan, China. Potential risk factors of AKI as well as the relation between AKI and in-hospital mortality were investigated.

Results

A total of 275 COVID-19 patients with ARDS were included in the study, and 49.5% of them developed AKI during their hospital stay. In comparison with patients without AKI, patients who developed AKI were older, tended to have chronic kidney disease, had higher Sepsis-Related Organ Failure Assessment score on day 1, and were more likely to receive invasive ventilation and develop acute organ dysfunction. Multivariate analysis showed that age, history of chronic kidney disease, neutrophil-to-lymphocyte ratio, and albumin level were independently associated with the occurrence of AKI. Importantly, increasing AKI severity was associated with increased in-hospital mortality when adjusted for other potential variables: odds ratio of stage 1 = 5.374 (95% CI: 2.147–13.452; p < 0.001), stage 2 = 6.216 (95% CI: 2.011–19.210; p = 0.002), and stage 3 = 34.033 (95% CI: 9.723–119.129; p < 0.001).

Conclusion

In this multicenter retrospective study, we found that nearly half of COVID-19 patients with ARDS experienced AKI during their hospital stay. The coexistence of AKI significantly increased the mortality of these patients.