The study will compare a novel calculation model (HeProCalc AB) with a standard weight-based and activated clotting time adjusted calculation for the dosing of Heparin and protamine and assess the impact on postoperative bleeding and blood transfusions after cardiac surgery.

During cardiac surgery with cardiopulmonary bypass (CPB), efficient anticoagulation is required in order to avoid microscopic clot formation or, in worst case, massive lift threatening thrombus formation. Heparin is by far the most common drug used to prevent blood from coagulating during CPB. Activated clotting time (ACT) is a point-of-care test of fibrin clotting time that has to be well prolonged to initiate safe CPB.

Following weaning from CPB, heparin is reversed by protamine. Administration of excess doses of protamine may have a deleterious effect on coagulation and contribute to postoperative bleeding with need of blood transfusions. In connection with CPB management, heparin and protamin doses are commonly calculated using body weight and ACT. However, a new Heparin-Protamin-Calculation computer program (HeProCalc) has been developed to provide patient titrated dosing of both heparin and protamin. However, any benefits regarding postoperative bleeding and transfusions has not been thoroughly investigated.

Inclusion Criteria:

• Patients undergoing cardiac surgery with the use of cardiopulmonary bypass
• Indication and planned use of heparin and protamine

Exclusion Criteria:

• Inability to leave informed consent or understanding the outline of the study
• Known coagulation disorder

On a group level in the planned publication. Upon request we will will share de-identified original data.