Objective: Nowadays, the coagulation status of the cardiac surgical patient is monitored using standard laboratory parameters. However, these tests involve long turnaround times, a critical limitation in settings where the patient’s coagulation status can change very quickly.  The aim of the present study is to describe, through serial blood controls, traditional tests and Point Of Care (POC), the coagulation status of patients undergoing cardiopulmonary bypass (CPB). Design: Observational study. Setting: Azienda Ospedaliero Universitaria Città della Salute e della Scienza di Torino, University of Turin, Italy. Partecipants: We enrolled 29 patients undergoing cardiopulmonary bypass for cardiac surgery at the ‘Città della Salute e della Scienza’ University Hospital in Turin  between March and June 2021. Interventions: In all patients 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 transfusions). 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). An additional sample was obtained (both at T1 and T2)  for ROTEM analysis. Measurements and Main results: Between the beginning and the end of the bypass we observed a significant decrease in coagulation factors II, X, XI, XII, protein C and S with an average percentage decrease of 32.58%, 34.11%, 36.69 %, 47.45%, 33.65% and 30.20%, respectively.  Regarding viscoelastic parameters, we recorded a median  increase of 22.64% of CT in Intem during CPB, with a reduction in MCF in Fibtem of 16.66%, as well as platelet contribution (MCF Extem-Fibtem), which was reduced by 7.69%. Conclusions: CPB-induced coagulopathy involve dilution, activation and consumption of all components of haemostasis, together with the need for profound anticoagulation.  Our data seem to confirm the important reduction of all coagulation factors and platelets, together with a consensual change in traditional laboratory and viscoelastic parameters.