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 ECCO_2-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 ECCO_2-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. V_T was set at 6 mL/kg predicted body weight then ECCO₂R was assessed to facilitate ultra-protective low V_T 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 V_T 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.