Protocol of VV-ECMO in Adult ARDS

Figure ​Figure11 summarizes our therapeutic protocol of VV-ECMO used for ARDS in adults. Our techniques of VV-ECMO are also described in our previous publications.^12,15–17 We use the Capiox emergent bypass system (Terumo Inc, Tokyo, Japan) and the 2-cannula method (DLP Medtronic, Minneapolis, MN; femoral inflow cannula: 19–23 French, jugular outflow cannula: 17–21 French) to perform VV-ECMO via percutaneous cannulation. Initially, we maximize the sweep gas flow (10 L/min, pure oxygen) to rapidly remove CO₂, and gradually increase the ECMO pump flow to achieve the best pulse oximetry-detected oxyhemoglobin saturation (S_pO₂). To rest the lungs, we downgrade the setting of MV to a lung-protective level step-by-step. At first, we use a pressure-control ventilation (PCV) with a peak airway pressure (PIP) ≤35 cmH₂O and a moderate positive end expiratory pressure (PEEP; often 12–16 cmH₂O) to obtain an estimated V_T ≤6 mL/kg/min under VV-ECMO. Then we take the arterial and the post-oxygenator blood samples repeatedly to adjust the sweep gas flow and the blood flow of VV-ECMO to provide an optimal arterial oxygenation that allows a downgrade in the PIP (to ≤30 cmH₂O) and the F_iO₂ (to 0.4) of MV. The hemoglobin (Hb) is kept ≥ 10 g/dL to increase the capacity of oxygenation. A modest volume replacement with packed red blood cell is provided to maintain a steady ECMO blood flow ≥3 L/min. We use loop diuretics (usually Furosemide in continuous dripping) or continuous renal replacement therapy (CRRT, in patients with renal shutdown) to achieve a negative fluid balance to dry the lungs.^18,19 We use systemic heparinization to anticoagulate the patient-ECMO circulation and keep the activated partial thromboplastin time (aPTT) around 40 to 55 seconds. If the patient shows significant improvements, we would try to wean him/her from VV-ECMO as long as the arterial oxygenation could be maintained under the LPV (PIP ≤35cmH₂O and MV F_iO₂ ≤0.6).

The therapeutic protocol of severe acute respiratory distress syndrome in adults. APTT = activated partial thromboplastin time, ARDS = acute respiratory distress syndrome, F_iO₂ = fraction of inspired oxygen, Hb = hemoglobin, MAP = mean arterial pressure, MV = mechanical ventilation, NO = nitric oxide, P_aO₂ = arterial oxygen tension, P_aCO₂ = arterial tension of carbon dioxide, PEEP = positive end-expiratory pressure, PIP = peak inspiratory pressure, SaO2 = arterial oxygen saturation, V_T = tidal volume, VV-ECMO = venovenous extracorporeal membrane oxygenation.