Less is more: We are administering too much protamine in cardiac surgery

Protamine is routinely administered to neutralize the anticlotting effects of heparin, traditionally at a dose of 1 mg for every 100 IU of heparin-a 1:1 ratio protamine sparing effects-but this is based more on experience and practice than literature evidence. The use of Hemostasis Management System (HMS) allows an individualized heparin and protamine titration. This usually results in a decreased protamine dose, thus limiting its side effects, including paradox anticoagulation.

This study aims to assess how the use of HMS allows to reduction of protamine administration while restoring the basal activated clotting time (ACT) at the end of cardiac surgery.

A retrospective observational study in a tertiary care university hospital.

We analyzed data from 42 consecutive patients undergoing cardiopulmonary bypass (CPB) for cardiac surgery. For all patients HMS tests were performed before and after CPB, to determine how much heparin was needed to reach target ACT, and how much protamine was needed to reverse it.

At the end of cardiopulmonary bypass, 2.2 ± 0.5 mg/kg of protamine was sufficient to reverse heparin effects. The protamine-to-heparin ratio was 0.56:1 over heparin total dose (a 44% reduction) and 0.84:1 over heparin initial dose (a 16% reduction).

A lower dose of protamine was sufficient to revert heparin effects after cardiopulmonary bypass. While larger studies are needed to confirm these findings and detect differences in clinically relevant outcomes, the administration of a lower protamine dose is endorsed by current guidelines and may help to avoid the detrimental effects of protamine overdose, including paradox bleeding.