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Difficulty: MediumHemodynamic and Coagulation Processes

An inpatient in their sixties is currently receiving treatment on the medical ward for a severe exacerbation of chronic obstructive pulmonary disease. Their therapeutic regimen includes intravenous methylprednisolone, scheduled bronchodilators, and subcutaneous unfractionated heparin for deep venous thrombosis prophylaxis. Upon admission 66 days ago, their platelet count was 310,000 /mm3310,000 \text{ /mm}^3 and hemoglobin was 14.8 g/dL14.8 \text{ g/dL}. Today, the patient reports acute, progressive pain in the left lower extremity. Physical examination demonstrates asymmetric swelling, warmth, and tenderness of the left calf. A bedside compression ultrasonography reveals an acute, non-compressible thrombus in the left popliteal vein. Stat laboratory evaluation shows a current platelet count of 145,000 /mm3145,000 \text{ /mm}^3, with a normal prothrombin time and activated partial thromboplastin time. Based on the most likely diagnosis, which of the following is the most appropriate next step in the pharmacologic management of this patient?

  1. A
    Discontinue unfractionated heparin and initiate subcutaneous enoxaparin
  2. B
    Discontinue prophylactic unfractionated heparin and initiate a therapeutic unfractionated heparin infusion
  3. Discontinue unfractionated heparin and initiate an argatroban infusionAnswer
  4. D
    Discontinue unfractionated heparin and immediately initiate oral warfarin
  5. E
    Continue unfractionated heparin and administer a prophylactic platelet transfusion

Answer

Discontinue unfractionated heparin and initiate an argatroban infusion.
This patient's clinical presentation is highly suspicious for heparin-induced thrombocytopenia (HIT) Type II. HIT is an immune-mediated prothrombotic disorder caused by IgG antibodies directed against heparin-platelet factor 4 (PF4) complexes. It typically presents 55 to 1010 days after heparin initiation with a platelet count drop of greater than 50%50\% and paradoxical thrombosis (venous or arterial). The immediate and most critical step in management is to discontinue all forms of heparin (including prophylactic doses and heparin flushes) and initiate a non-heparin anticoagulant, such as a direct thrombin inhibitor (e.g., argatroban, bivalirudin).

Step-by-Step Solution

1
Calculate the 4T score to assess the probability of heparin-induced thrombocytopenia (HIT).
The patient has a >50%>50\% drop in platelets (310,000310,000 to 145,000145,000), appropriate timing (day 66 of therapy), and a new thrombosis (deep venous thrombosis), indicating a high probability of HIT.
A high 4T score necessitates the immediate cessation of all heparin-containing products to halt the immune-mediated prothrombotic cascade.
2
Identify the appropriate alternative anticoagulant for acute management.
A non-heparin anticoagulant, such as a direct thrombin inhibitor (e.g., argatroban, bivalirudin) or fondaparinux, must be initiated.
These agents do not cross-react with circulating HIT antibodies, whereas low-molecular-weight heparins (like enoxaparin) do and are contraindicated.

Key Concept

Management of Heparin-Induced Thrombocytopenia (HIT) Type II
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Topics

Hemodynamic and Coagulation Processes

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