Electronic supplementary material (ESM)

Lower tidal volume strategy (≈ 3 ml/kg) combined with extracorporeal CO2 removal versus ‘conventional’ protective ventilation (6 ml/kg) in severe ARDS *

* the prospective randomized Xtravent-study

Thomas Bein1*, Steffen Weber-Carstens2*, Anton Goldmann2, Thomas Müller3, Thomas Staudinger4, Jörg Brederlau5, Ralf Muellenbach6, Rolf Dembinski7, Bernhard M Graf1 , Marlene Wewalka8, Alois Philipp9, Klaus-Dieter Wernecke 2,10, Matthias Lubnow3, Arthur S Slutsky9

1. Evaluation, cannulation and clinical monitoring for avECCO2-R

Evaluation, cannulation and clinical monitoring for avECCO2-R followed a strict algorithm in all participating centers. Patients had to have a platelet count > 60.000/µl and a partial thromboplastin time (PTT) < 60 sec. prior to cannulation. After ultrasonographic assessment of the diameters of the femoral artery and of the contralateral femoral vein, cannulation was performed by experienced physicians using Seldinger’s technique. The size of the arterial cannula never exceeded 15 French (Fr) and was individually selected, based on vessel diameter to ensure a residual lumen cross-sectional area ≥ 30%. The venous cannula was typically selected two sizes larger (17 Fr) to maintain low flow resistance. The iLA system runs with “low dose” heparin (600-800 IU/h) infusion, which does not exceed normal antithrombotic anticoagulation requirements (PTT 40-50 sec). Perfusion monitoring of the lower extremities included continuous limb pulse oxymetry distal to the arterial cannulation site, determination of serum lactate and creatine kinase levels, as well as clinical inspection for any signs of decreased perfusion and/or ischemia.

2. Termination of the avECCO2-R therapy and decannulation:

After the patient’s lung disease improved (FiO2 < 0.5, PEEP £ 12 cm H2O, assisted spontaneous breathing) and intensity of mechanical ventilation was decreased, weaning from the iLA-system was initiated by starting a “cessation trial” (reduction of sweep oxygen gas flow to 1 l/min) for a duration of 2 hrs. If no major deterioration of gas exchange variables was observed and no significant increase in patient`s minute volume ventilation or tachypnea (> 40 breath per min) occurred, the cannulae were manually removed, followed by continuous compression of cannulation sites for at least 30 min. Thereafter, a pressure bandage was applied for 24 hrs. Deterioration of the patient during the cessation trial resulted in an increase of sweep gas flow and a repetition of the trial next day.

3. Figure 5: Assessment of awakeness (RASS score), daily cumulative infusion of benzodiazepines (midazolam) in the treatment and control groups during the study period.

Fig. 5A: Mean RASS score, Fig. 5B: Daily cumulative midazolam infusion

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