Dose for Reversal of Heparin After Cardiopulmonary Bypass

Heparin is routinely administered during cardiopulmonary bypass (CPB) to prevent clot formation in the extracorporeal circuit. At the end of CPB, protamine sulfate is used to neutralize the anticoagulant effect of heparin. The conventional protamine dosing strategy is 1 mg of protamine for every 100 IU of the initial heparin dose administered. However, emerging evidence suggests that this standard dosing regimen may result in excessive protamine exposure, which has been associated with adverse effects such as hypotension, pulmonary hypertension, platelet dysfunction, and paradoxical anticoagulation.

Recent studies have suggested that reduced protamine dosing strategies may achieve adequate reversal of heparin anticoagulation while minimizing potential complications associated with protamine administration. However, the optimal protamine-to-heparin ratio remains uncertain.

This randomized clinical study aims to compare different protamine dosing strategies for heparin reversal after cardiopulmonary bypass in adult patients undergoing cardiac surgery. Participants will be randomized to receive one of three protamine dosing regimens based on the initial heparin dose administered during CPB: the conventional 1:1 ratio (1 mg protamine per 100 IU heparin), a reduced dose ratio of 0.8:1, or a further reduced ratio of 0.75:1.

The study will evaluate the effectiveness of these dosing strategies in achieving adequate heparin reversal as measured by activated clotting time (ACT), as well as clinical outcomes including the need for additional protamine administration, postoperative bleeding, transfusion requirements, protamine-related adverse events, re-exploration for bleeding, and duration of intensive care unit stay.

Inclusion criteria

• Age ≥18 years
• Patients scheduled for elective cardiac surgery requiring cardiopulmonary bypass (CABG, valve surgery, or combined procedures)
• Patients receiving systemic heparinization according to the institutional cardiopulmonary bypass protocol
• Ability to provide written informed consent before surgery

Exclusion criteria

• Known allergy or hypersensitivity to protamine
• Pre-existing coagulopathy or bleeding disorders
• Patients receiving chronic anticoagulation that cannot be safely discontinued before surgery
• Severe renal dysfunction
• Severe hepatic dysfunction
• Emergency cardiac surgery
• Pregnancy
• Off-pump cardiac surgery