A 62-year-old woman is evaluated on postoperative day 5 following a right hemicolectomy fo… — USMLE Step 2 CK

A $62$ -year-old woman is evaluated on postoperative day $5$ following a right hemicolectomy for stage III colon adenocarcinoma. She has been receiving subcutaneous unfractionated heparin for deep vein thrombosis prophylaxis. Today, she reports sudden-onset right lower extremity pain and swelling, mild shortness of breath, and nausea. Vital signs are temperature $37.8^\circ \text{C}$ ( $100^\circ \text{F}$ ), blood pressure $135/85\text{ mmHg}$ , pulse $102\text{ /min}$ , and respirations $20\text{ /min}$ . Physical examination shows a swollen, erythematous, and tender right calf. The abdomen is mildly distended but non-tender with hypoactive bowel sounds. Lungs are clear to auscultation. Laboratory studies show:

Hemoglobin: $11.2\text{ g/dL}$
Platelet count: $65,000/\mu\text{L}$ (baseline prior to surgery was $250,000/\mu\text{L}$ )
Leukocyte count: $8,500/\mu\text{L}$

Prothrombin time (PT): $12.5\text{ seconds}$
Partial thromboplastin time (PTT): $32\text{ seconds}$

Sodium: $138\text{ mEq/L}$
Potassium: $4.2\text{ mEq/L}$
Blood urea nitrogen: $16\text{ mg/dL}$
Creatinine: $0.9\text{ mg/dL}$

Lower extremity venous duplex ultrasonography confirms an acute deep vein thrombosis in the right popliteal vein. Which of the following is the most appropriate next step in management?

Discontinue unfractionated heparin and initiate argatroban therapyAnswer
B
Continue unfractionated heparin and order computed tomography of the abdomen and pelvis
C
Discontinue current medications and initiate empiric broad-spectrum intravenous antibiotics
D
Administer intravenous furosemide and obtain a transthoracic echocardiogram
E
Insert a nasogastric tube and initiate conservative management for bowel obstruction

Answer

Discontinue unfractionated heparin and initiate argatroban therapy

The correct management is to discontinue unfractionated heparin and initiate a direct thrombin inhibitor such as argatroban. This patient presents with heparin-induced thrombocytopenia (HIT) type 2, an immune-mediated disorder caused by IgG autoantibodies against platelet factor 4 (PF4)-heparin complexes. This leads to platelet activation, a profound drop in platelet count (typically

>50\%

), and a highly prothrombotic state. The classic presentation occurs

5

10

days after heparin initiation. The '4 T's' score for this patient is high (Thrombocytopenia

>50\%

, Timing day 5, Thrombosis present, no oTher clear cause). The most critical next step is immediate cessation of all heparin products and initiation of a non-heparin anticoagulant to prevent further venous or arterial thrombosis.

Step-by-Step Solution

Analyze the patient's presentation and laboratory findings.

The patient has a new-onset deep vein thrombosis (DVT) and a

>50\%

drop in platelets on postoperative day 5 while receiving unfractionated heparin.

Recognizing the timing and magnitude of the thrombocytopenia alongside a new thrombotic event is critical for the diagnosis.

Calculate the clinical probability of Heparin-Induced Thrombocytopenia (HIT) using the 4T's score.

The patient scores high (2 points for

>50\%

platelet drop, 2 points for day 5 timing, 2 points for new thrombosis, and 2 points for no obvious other cause), yielding an 8/8.

A high 4T score indicates a strong clinical probability of HIT, requiring immediate intervention before confirmatory laboratory testing.

Determine the appropriate initial management for suspected HIT.

All heparin products must be discontinued immediately, and a non-heparin anticoagulant (such as argatroban or bivalirudin) must be started.

Continuing heparin worsens the immune-mediated prothrombotic state, and therapeutic anticoagulation is needed to manage the new DVT and prevent further life-threatening complications.

Key Concept

Heparin-Induced Thrombocytopenia (HIT) Diagnosis and Management

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