Years later, similar findings were described in cardiac surgery patients.26 Interestingly, hemolysis is also involved in pulmonary hypertension, a frequent complication of severe ARDS.27 To our knowledge, the current study is the first to describe an association of indirect signs of hemolysis such as COHb and haptoglobin with vascular tone in ECMO patients. Here, HP is linked to acute respiratory distress syndrome.