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Difficulty: HardPharmacologic Interventions

A 6262-year-old woman is evaluated in the hospital for new-onset swelling and pain in her right lower extremity. She was admitted 66 days ago for an acute pulmonary embolism and was immediately started on a continuous intravenous infusion of unfractionated heparin. Her respiratory status has significantly improved, but today she reports severe calf pain. Vital signs are within normal limits. Physical examination shows a right calf that is swollen, erythematous, and tender to palpation. Duplex ultrasonography confirms a new deep vein thrombosis in the right popliteal vein. Laboratory studies show a platelet count of 95,000/μL95,000/\mu L, a significant decline from her admission platelet count of 260,000/μL260,000/\mu L. Renal and hepatic function tests are within normal limits. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

  1. Discontinue unfractionated heparin and initiate an argatroban infusionAnswer
  2. B
    Discontinue unfractionated heparin and initiate oral warfarin therapy
  3. C
    Switch from unfractionated heparin to subcutaneous enoxaparin
  4. D
    Discontinue unfractionated heparin and transfuse pooled donor platelets
  5. E
    Discontinue unfractionated heparin and administer intravenous protamine sulfate

Answer

Discontinue unfractionated heparin and initiate an argatroban infusion
The correct intervention is to discontinue unfractionated heparin and initiate a direct thrombin inhibitor, such as argatroban. This patient's presentation of a new thrombotic event (deep vein thrombosis) coupled with a platelet count drop of greater than 50% within 5 to 10 days of heparin initiation is classic for type 2 heparin-induced thrombocytopenia (HIT). HIT is a life-threatening, immune-mediated prothrombotic disorder caused by antibodies against heparin-platelet factor 4 (PF4) complexes. The cornerstone of management is the immediate cessation of all heparin products and the initiation of a non-heparin anticoagulant to treat the active thrombosis and underlying hypercoagulable state.

Step-by-Step Solution

1
Evaluate the clinical presentation and laboratory timeline.
The patient developed a new thrombosis (DVT) and a >50% drop in platelet count exactly 6 days after starting unfractionated heparin.
This specific temporal relationship and clinical picture (thrombosis plus thrombocytopenia) yields a high 4T score, strongly indicating type 2 Heparin-Induced Thrombocytopenia (HIT).
2
Determine the necessary acute intervention for the primary drug involved.
All forms of heparin (unfractionated and low-molecular-weight) must be immediately discontinued.
HIT is caused by IgG antibodies against the heparin-platelet factor 4 (PF4) complex, leading to widespread platelet activation. Ongoing exposure will perpetuate the prothrombotic state.
3
Select the appropriate alternative pharmacologic therapy for the new thrombosis.
A non-heparin anticoagulant, such as a direct thrombin inhibitor (e.g., argatroban, bivalirudin) or fondaparinux, must be initiated.
The patient has an active new DVT and an underlying hypercoagulable state requiring immediate, safe anticoagulation without cross-reactivity.

Key Concept

Management of Heparin-Induced Thrombocytopenia (HIT)
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Topics

Pharmacologic Interventions

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