Warfarin skin necrosis occurs within the first 2 to 3 days after starting warfarin therapy because:

a. The platelet count decreases to fewer than 100 ´ 109/L, and significant bleeding occurs.
b. Protein C decreases significantly before full anticoagulation, and skin thrombosis results.
c. Prothrombin decreases rapidly generating less thrombin, and significant bleeding occurs.
d. Plasminogen increases, and rapid clot lysis occurs.

ANS: B
Protein C has a 6-hour half-life, and so it rapidly decreases when warfarin therapy is begun, along with factor VII (both are vitamin K–dependent proteins). Full anticoagulation with warfarin is not obtained until factors X and prothrombin are decreased to less than 50%, requANS: B
Protein C has a 6-hour half-life, and so it rapidly decreases when warfarin therapy is begun, along with factor VII (both are vitamin K–dependent proteins). Full anticoagulation with warfarin is not obtained until factors X and prothrombin are decreased to less than 50%, requiring 4 to 7 days based on their half-lives. Because protein C is important in controlling clot formation, its decrease actually puts the patient in a prethrombotic state until full anticoagulation is obtained.
iring 4 to 7 days based on their half-lives. Because protein C is important in controlling clot formation, its decrease actually puts the patient in a prethrombotic state until full anticoagulation is obtained.