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Ronco C, Bagshaw SM, Bellomo R, Clark WR, Husain-Syed F, Kellum JA, Ricci Z, Rimmelé T, Reis T, Ostermann M: Extracorporeal Blood Purification and Organ Support in the Critically Ill Patient during COVID-19 Pandemic: Expert Review and Recommendation. Blood Purification DOI 10.1159/000508125
The COVID-19 pandemic has presented many challenges in treatment and organ support. The “cytokine storm” commonly associated with severe forms of COVID-19 raises the possibility of using extracorporeal blood purification technologies for treatment.
Ronco and colleagues provide an in-depth review of the rationale, pathophysiology, and possible benefits of this approach, collectively known as extracorporeal organ support, or ECOS. These strategies incorporate continuous renal replacement therapy (CRRT), extracorporeal membrane oxygenation (ECMO), and extracorporeal carbon dioxide removal (ECCO2R). The utility of ECOS in restoring a balanced systemic immune response (relieving “cytokine storm”) involves strategies such as high-volume hemofiltration, hemoperfusion, plasmapheresis, coupled filtration adsorption, high cut-off (HCO), and membranes with enhanced adsorptive profiles (CytoSorb and oXiris).
CRRT has advantages over intermittent hemodialysis in hemodynamically unstable patients, but whether it provides better outcomes in COVID-19 patients with acute kidney injury (AKI) is uncertain. CRRT can be combined with ECMO or ECCO2R in certain circumstances. More effective removal of cytokines can be accomplished with CytoSorb or oXiris devices. The CytoSorb device has been given conditional approval for use in COVID-19 patients with severe disease by the FDA. So far there have been no comparisons of systemic immunomodulatory therapy (e.g., IL-6 inhibition by tocilizumab or steroids) with ECOS. Importantly, efficacy has not yet been proven for these adsorptive devices by RCT. ECCO2R may be particularly useful in patients with hypercapnic acute respiratory failure unaccompanied by the need for substantial oxygen support.
HCO membranes have been tried in multiorgan failure due to endotoxemia and sepsis, but the results have been disappointing. The timing of application of these devises may be crucial, and the “window of opportunity” short in duration.
AKI is very common (20–40%) in severe COVID-19 requiring ventilatory support. The pathogenesis of this event is poorly understood, but in most cases does not seem to be due to direct invasion by the SARS-CoV-2 virus itself. CRRT is very useful in treating the AKI but clotting of the filters is a major issue because of the thrombophilic state engendered by COVID-19. Special anticoagulation regimens and predilution continuous veno-venous hemodialysis (CVVHD) may help to partially alleviate this problem.
All in all, this review is a very useful and detailed guide to the current state of ECOS in COVID-19. All caregivers with extensive exposure to COVID-19 patients would benefit from reading it in its original form.
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