Anemia is common in intensive care unit (ICU) patients and often appears early in the ICU course. The optimal management red blood cells RBC transfusion in critically ill patients remains controversial and clinical studies in this field have usually been based on transfusion thresholds. In the "TRICC" Trial, patients assigned to a restrictive transfusion strategy (transfusion if Hb<7 g/dL) had similar mortality to patients transfused if Hb<10 g/dL. Notably, none of the large RCT tried to focus on a personalize RBC transfusion protocol, i.e. a transfusion protocol which address the individual need for transfusion basing on physiological approach. We therefore hypothesized that patients with high extraction of oxygen could benefit more of RBCs transfusion regardless their hemoglobin levels.

Inclusion Criteria:

• Hemoglobin level <10 g/dL during the first 72 hours of ICU

Exclusion Criteria:

• Acute bleeding
• Hemoglobin level less than 7 g/dL

Unselected critically ill patients admitted to intensive care unit