Certified Registered Nurse Infusion (CRNI) Practice Exam 2025 – All-in-One Comprehensive Guide to Exam Success!

Heparin sodium primarily acts as an anticoagulant by enhancing the activity of antithrombin III, which inhibits thrombin. At low doses, heparin specifically prevents the conversion of prothrombin to thrombin. Thrombin is a key enzyme in the coagulation cascade that ultimately leads to the formation of fibrin from fibrinogen, thereby playing a crucial role in blood clot formation. By inhibiting thrombin, low doses of heparin effectively reduce the formation of clots, making it an essential medication in the management of various thromboembolic conditions.

The other substances mentioned, such as fibrin, platelets, and prothrombinase, are involved in the coagulation process but are not the primary target of low-dose heparin. Fibrin is the end product of the coagulation cascade, while platelets are involved in the initial stages of clot formation. Prothrombinase is a complex that converts prothrombin to thrombin, but at low doses, heparin’s direct action is primarily on thrombin itself.