A 62-year-old man is evaluated on the medical ward for new-onset right calf swelling and p… — USMLE Step 3

A $62$ -year-old man is evaluated on the medical ward for new-onset right calf swelling and pain. He was admitted $6$ days ago for severe community-acquired pneumonia and was started on intravenous antibiotics and subcutaneous unfractionated heparin for deep vein thrombosis prophylaxis. Vital signs are temperature $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure $128/82\text{ mmHg}$ , pulse $88/\text{min}$ , and respirations $16/\text{min}$ . Physical examination reveals a swollen, erythematous, and tender right calf. A lower extremity venous duplex ultrasound confirms a proximal deep vein thrombosis in the right popliteal vein. Laboratory studies from today are compared to admission values:

Laboratory Test	Current Value	Admission Value
Platelet count	$55,000/\text{mm}^3$	$240,000/\text{mm}^3$
Hemoglobin	$13.5\text{ g/dL}$	$13.8\text{ g/dL}$
Serum creatinine	$1.1\text{ mg/dL}$	$1.0\text{ mg/dL}$

Which of the following is the most appropriate pharmacologic intervention for this patient?

Intravenous argatrobanCevap
B
Subcutaneous enoxaparin
C
Oral warfarin
D
Intravenous platelet transfusion
E
Discontinuation of unfractionated heparin without alternative anticoagulation

Cevap

Intravenous argatroban

The correct answer is intravenous argatroban. This patient has developed Heparin-Induced Thrombocytopenia (HIT) with thrombosis, specifically a new right lower extremity deep vein thrombosis. HIT is an immune-mediated adverse drug reaction characterized by a platelet count drop of greater than 50% occurring 5-14 days after heparin exposure. The immediate management of HIT requires the absolute discontinuation of all heparin products (including flushes) and the immediate initiation of a non-heparin anticoagulant. Direct thrombin inhibitors (such as argatroban or bivalirudin) or the factor Xa inhibitor fondaparinux are the preferred pharmacologic interventions to manage the highly prothrombotic state associated with HIT.

Adım Adım Çözüm

Calculate the magnitude and timing of the platelet drop.

The platelet count has dropped by >50% (from 240,000 to 55,000) exactly 6 days after the initiation of unfractionated heparin.

This timeline and magnitude highly suggest Heparin-Induced Thrombocytopenia (HIT).

Correlate laboratory findings with clinical presentation.

The patient has developed a new deep vein thrombosis concurrently with the drop in platelets.

This confirms a highly prothrombotic state characteristic of HIT with thrombosis (HITT).

Determine the necessary pharmacologic intervention.

All heparin products must be immediately discontinued, and a non-heparin anticoagulant (like argatroban) must be initiated.

Stopping heparin alone is insufficient because the patient has an active thrombosis and an ongoing hypercoagulable state.

Anahtar Kavram

Management of Heparin-Induced Thrombocytopenia (HIT) with thrombosis requires immediate cessation of all heparin products and initiation of a non-heparin anticoagulant (e.g., argatroban, bivalirudin, or fondaparinux).

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

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