Blood samples and laboratory tests
In all patients enrolled in the present study two series of blood samples were performed at T1 (before the start of CPB, after sternum opening, before UFH administration) and at T2 (after the end of CPB, after protamine administration and before any blood component transfusion). Laboratory tests included blood count, INR, aPTT, Fibrinogen and functional assay of coagulation factors (AT III, factors II, V, VII, VIII, IX, X, XI, XII, proteins C and S), with results expressed as percentage of activity. An additional sample was obtained (both at T1 and T2) for performing ROTEM analysis.