difficult enrollment after the primary investigator left the centre

An hematocrit of 21-25% is supposed to perform the best organ protection during cardiopulmonary bypass for cardiac surgery.

The investigators want to establish the best timing for a transfusion (in patients with a predicted low hematocrit during cardiopulmonary bypass) and the efficacy of preprocedural hemodilution (in patients with a predicted high hematocrit during cardiopulmonary bypass) in patients undergoing cardiac surgery.

Inclusion Criteria:

• Undergoing cardiac surgery

Exclusion Criteria:

• Age < 18 years old
• Not signing written consent
• Age < 65 years old (subgroup 1)
• Emergency, aortic stenosis, main left coronary stenosis (subgroup 2)