Coronary artery and coronary sinus lactate levels and myocardial oxygen extraction during the protocol. Lactate levels (panel A) steeply rise during cardiac arrest in both arms. In the FS arm, lactate rise persists even during the first ECMO treatment and reaches significantly higher plateau levels than in the FF arm both for arterial and CS values (P = 0.016 and P = 0.035, respectively). Significantly higher levels in the FS arm persist during the rest of the protocol, however in both arms a downward trend can be detected, though more pronounced in the FF arm. Myocardial oxygen extraction in ml O2/L (panel B) markedly increases during cardiac arrest followed by a steep decline after starting both ECMO regimens. Values after ECMO start are not significantly different (see text).