Lung (extracorporeal CO2 removal) and renal (continuous renal replacement therapy) support: the role of ultraprotective strategy in Covid 19 and non-Covid 19 ARDS. A case-control study

Background: Preliminary studies suggest that moderate ARDS and acute renal failure might benefit from extracorporeal CO2 removal (ECCO2R) coupled with CRRT. However, evidence is limited and potential for this coupled treatment may need to be explored. The aim of the present study was to evaluate whether a protective driving pressure was obtained applying low-flow ECCO2-R plus CRRT in patients affected by moderate ARDS with COVID-19 compared to an historical group without COVID-19. Methods: A case-control study has been conducted comparing a group of consecutive moderate ARDS patients presenting AKI and affected by COVID-19, who needed low-flow ECCO2-R plus CRRT to achieve an ultra-protective ventilatory strategy, with historical group without COVID-19 that matched for clinical presentation and underwent the same ultra-protective treatment. VT was set at 6 mL/kg predicted body weight then ECCO2R was assessed to facilitate ultra-protective low VT ventilation to preserve safe Pplat and low driving pressure. Results: ECCO2R+CRRT reduced the driving pressure from 17 (14-18) to 11.5 (10-15) cmH2O (p<0.0004) in the fourteen ARDS patients by decreasing VT from 6.7 ml/kg PBW (6.1-6.9) to 5.1 (4.2-5.6) after 1 hour (p <0.0001). In the ARDS patients with COVID-19, the driving pressure reduction was more effective from baseline 18 (14-24) cmH2O to 11 (10-15) cmH2O (p<0.004), compared to the control group from 15 (13-17) to 12(10-16) cmH2O (p< 0.03), after one hour. ECCO2R+CRRT did not affected 28 days mortality in the two groups, while we observed a shorter duration of mechanical ventilation (19 {7-29} vs 24 {22-38} days; p=0.24) and ICU length of stay (19 {7-29} vs 24 {22-78} days; p=0.25) in moderate ARDS patients with COVID-19 compared to control group. Conclusions: In moderate ARDS patients with or without COVID-19 disease, ECCO2R+CRRT may be and effective supportive treatment to reach protective values of driving pressure unless severe oxygenation defects arise requiring ECMO therapy initiation.