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Difficulty: Very hardHematology and Oncology

A 58-year-old man is hospitalized for a newly diagnosed left lower extremity deep vein thrombosis. He has a history of hypertension and type 2 diabetes mellitus. On admission (Day 1), he was started on a continuous intravenous unfractionated heparin infusion and oral warfarin.

Today (Day 6 of hospitalization), the patient complains of severe pain and dark purple discoloration over his right toes and the heel of his left foot.

Vital signs are temperature 37.0°C (98.6°F), blood pressure 135/85 mm Hg, pulse 98/min, and respirations 16/min.

Physical examination reveals well-demarcated, necrotic, purpuric lesions on the toes of the right foot and the heel of the left foot. The left leg is edematous but unchanged from admission. Peripheral pulses are palpable bilaterally.

Laboratory results are as follows:

ParameterDay 1 (Admission)Day 6 (Today)
Hemoglobin14.2 g/dL13.8 g/dL
Platelets260,000/mm³115,000/mm³
Prothrombin time (PT)12 sec26 sec
INR1.12.4
Activated partial thromboplastin time (aPTT)30 sec58 sec
Creatinine1.0 mg/dL1.0 mg/dL

Which of the following is the most appropriate next step in the management of this patient?

  1. Discontinue heparin and warfarin, administer vitamin K, and initiate argatrobanAnswer
  2. B
    Discontinue heparin, continue warfarin, and initiate argatroban
  3. C
    Discontinue warfarin, administer vitamin K, and continue the heparin infusion
  4. D
    Discontinue both medications and administer a platelet transfusion
  5. E
    Continue both medications and order a lower extremity arterial Doppler ultrasound

Answer

The most appropriate next step is to discontinue both heparin and warfarin, administer vitamin K, and initiate a non-heparin anticoagulant such as argatroban.
The correct answer addresses both components of this patient's pharmacologic crisis: Heparin-Induced Thrombocytopenia (HIT) and Warfarin-induced venous limb gangrene. HIT is diagnosed by the classic >50% drop in platelets 5 to 10 days after heparin initiation. Pathophysiologically, HIT causes massive systemic thrombin generation. Concurrently, the initiation of warfarin rapidly depletes Protein C, a natural anticoagulant with a very short half-life. The combination of high thrombin (from HIT) and low Protein C (from warfarin) causes catastrophic hypercoagulability resulting in microvascular thrombosis and venous limb gangrene. The correct management requires three distinct actions: 1) immediately stop heparin to halt the HIT immune reaction, 2) stop warfarin and administer vitamin K to rapidly replete Protein C, and 3) initiate a non-heparin anticoagulant (such as the direct thrombin inhibitor argatroban) to manage the underlying deep vein thrombosis.

Step-by-Step Solution

1
Evaluate the laboratory trends from admission to Day 6.
Platelets dropped from 260,000/mm³ to 115,000/mm³ (a >50% decrease).
A >50% relative drop in platelets occurring 5-10 days after starting heparin strongly suggests Heparin-Induced Thrombocytopenia (HIT).
2
Identify the etiology of the necrotic skin lesions on the lower extremities.
The lesions represent venous limb gangrene caused by the combination of HIT and warfarin therapy.
Warfarin rapidly depletes Protein C (a natural anticoagulant). When combined with the massive thrombin generation characteristic of HIT, this leads to severe microvascular thrombosis and gangrene.
3
Determine the appropriate multi-step pharmacologic intervention.
Stop heparin, stop warfarin, administer vitamin K, and start a direct thrombin inhibitor.
Heparin must be stopped to halt immune-mediated platelet activation. Warfarin must be stopped and reversed with vitamin K to replete Protein C levels. Argatroban provides necessary anticoagulation for the underlying DVT without triggering HIT antibodies.

Key Concept

Management of Heparin-Induced Thrombocytopenia (HIT) complicated by Warfarin-induced venous limb gangrene.
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Topics

Hematology and Oncology

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