See Heparin

Protein C is a vit. K-dependent anticoagulant activated by bound thrombin in the presence of endothelial thrombomodulin.

Protein C acts together with protein S to inactivate the activated forms of factors V and VIII, which are necessary for the production of thrombin.

Hypercoagulable States/ Thrombophilia

The most common cause is factor V Leiden mutation.

Tx - warfarin , target INR 2-3 for 6 months

Antiphospholipid Syndromes

2 main syndromes are the lupus anticoagulant and the anticardiolipin antibody. Both cause thrombosis.

Anticardiolipin antibodies are associated with multiple spontaneous abortions

They are the only cause of thrombophilia with an abnormality in the aPTT.

Dx

the best initial test = mixing study - aPTT will remain elevated even after the mix

The most accurate test = Russell viper venom test

Fondaparinux is a selective Xa inhibitor with a half-life of 17 hours administered subcutaneously and once daily in patients with NSTACS.

Although there is no risk of HIT, fondaparinux is renally excreted and is not recommended if estimated GFR is <20 ml/min/1.73 m2 .

Direct Thrombin Inhibitors

Bivalirudin (related to hirudin, the anticoagulant used by leeches), Argatroban, Dabigatran (only oral agent in class)