Warfarin necrosis

Warfarin Necrosis

Diagram of the coagulation cascade, illustrating the complex interactions involved in blood clotting.

Warfarin necrosis is a rare but serious complication associated with the use of the anticoagulant medication warfarin. It is characterized by the development of skin necrosis, which typically occurs within the first few days of starting warfarin therapy. This condition is a result of an imbalance in the coagulation system, leading to excessive clotting in small blood vessels and subsequent tissue death.

Pathophysiology

Warfarin acts by inhibiting the synthesis of vitamin K-dependent clotting factors, specifically factors II, VII, IX, and X, as well as proteins C and S. Protein C and Protein S are natural anticoagulants that help regulate the coagulation cascade. When warfarin is initiated, there is a rapid decline in protein C levels due to its shorter half-life compared to the procoagulant factors. This transient hypercoagulable state can lead to the formation of microthrombi in the dermal vasculature, resulting in skin necrosis.

Clinical Presentation

Warfarin necrosis typically presents within 3 to 10 days after the initiation of warfarin therapy. Patients may initially notice pain and erythema in affected areas, which are most commonly the breasts, thighs, buttocks, and abdomen. These areas can rapidly progress to purpura, bullae, and eventually necrosis. The necrotic tissue may become black and escharotic, requiring surgical debridement in severe cases.

Risk Factors

Several risk factors have been identified for the development of warfarin necrosis, including:

• Female gender
• Obesity
• High initial doses of warfarin
• Deficiency of protein C or protein S
• Previous history of thromboembolic events

Diagnosis

The diagnosis of warfarin necrosis is primarily clinical, based on the characteristic presentation and temporal relationship with the initiation of warfarin therapy. Laboratory tests may reveal a prolonged prothrombin time (PT) and a decrease in protein C and S levels. A skin biopsy can confirm the presence of microvascular thrombosis and necrosis.

Management

The management of warfarin necrosis involves the immediate discontinuation of warfarin and the administration of alternative anticoagulation, such as heparin. Vitamin K may be given to reverse the effects of warfarin. In cases of protein C deficiency, replacement therapy with protein C concentrate or fresh frozen plasma may be beneficial. Surgical intervention may be necessary for debridement of necrotic tissue.

Prevention

To prevent warfarin necrosis, it is recommended to start warfarin at a low dose and gradually increase it while overlapping with heparin until the therapeutic range is achieved. Monitoring of protein C and S levels may be considered in high-risk individuals.

Related Pages

• Warfarin
• Coagulation
• Protein C deficiency
• Anticoagulation