Abstract
Since SARS-CoV-2 spread through China at the end of 2019, COVID-19 has been probably the most difficult challenge in the last decades for healthcare systems all around the world, still representing a danger for fragile patients with different comorbidities. Chronic dialysis patients affected by COVID-19 experienced severe disease with a higher mortality rate compared to the general population. Morbidity and mortality of this severe acute respiratory syndrome depend on both acute respiratory failure and systemic immunological involvement with consequent inflammation-mediated injury. Indeed, the most important determining factor of COVID-19 severity is the strength of the so-called "cytokine storm" associated with SARS-CoV-2 infection. Therefore, this severe infection varies clinically from an asymptomatic condition to a generalized and violent inflammatory response and acute respiratory distress syndrome, with consequent pulmonary interstitial edema and a high risk of multi-organ failure. The use of extracorporeal therapies targeting cytokine clearance to improve patients' outcomes has been widely debated, especially in end-stage kidney disease's patients on maintenance dialysis or in individuals affected by acute kidney injury admitted to intensive care units. Different studies were conducted to demonstrate how specific dialyzers could decrease the COVID-19 inflammatory state. The aim of this narrative review was to summarize main studies about this topic, focusing primarily on the role of polymethylmethacrylate dialyzer and underlining pros and cons of this sorbent.