The primary aim of the study is to compare the number of RBC units transfused by group (standard group or optimization group) over a period of 5 days counted from the first decision of transfusion taken post-operative. Considering the randomisation and considering the 50 % reduction of the decisions of transfusion in the group optimization, the absolute blood savings is estimated 25 % for the whole population. Secondary end points include the number of side effects associated with transfusion or when avoiding transfusion, length of hospital stay, and hospital mortality as well as major adverse events.