A 65-year-old man is evaluated in the hospital for new-onset right lower extremity swellin… — USMLE Step 2 CK

A $65$ -year-old man is evaluated in the hospital for new-onset right lower extremity swelling and pain. He underwent a complex open cholecystectomy and lysis of adhesions $7$ days ago. His postoperative course was complicated by a superficial wound infection, which is currently being treated with targeted antibiotic therapy. Since the day of surgery, he has been receiving subcutaneous unfractionated heparin for deep venous thrombosis prophylaxis.

Vital signs include a temperature of $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), heart rate of $92/\text{min}$ , and blood pressure of $130/80\text{ mm Hg}$ . Physical examination reveals a swollen, erythematous, and tender right calf.

Laboratory studies show the following:

Test	Result
Hemoglobin	$11.2 \text{ g/dL}$
Leukocyte count	$8,500/\mu\text{L}$
Platelet count	$95,000/\mu\text{L}$
Preoperative platelet count	$220,000/\mu\text{L}$
Creatinine	$1.1 \text{ mg/dL}$

Lower extremity venous duplex ultrasonography reveals a noncompressible right popliteal vein.

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

Discontinue unfractionated heparin and start argatrobanCevap
B
Discontinue unfractionated heparin and start enoxaparin
C
Discontinue unfractionated heparin and start warfarin
D
Continue unfractionated heparin and start a therapeutic-dose continuous infusion
E
Administer pooled platelets and discontinue unfractionated heparin

Cevap

The most appropriate next step in management is to discontinue unfractionated heparin and start argatroban.

The correct action is to discontinue unfractionated heparin and initiate a direct thrombin inhibitor (e.g., argatroban). This patient has classic Type 2 Heparin-Induced Thrombocytopenia (HIT), defined by a fall in platelet count of

>50\%

occurring

5

10

days after heparin initiation, alongside a new thrombotic event (popliteal DVT). Pathophysiologically, IgG antibodies form against the heparin-platelet factor 4 (PF4) complex. These immune complexes bind to platelet surfaces, causing widespread platelet activation, consumption (leading to thrombocytopenia), and massive thrombin generation (leading to arterial and venous thrombosis). The absolute priority is to halt the immune trigger by stopping all heparin exposure and to provide immediate therapeutic anticoagulation using an alternative non-heparin agent (e.g., argatroban, bivalirudin, fondaparinux) to manage the profound prothrombotic state.

Adım Adım Çözüm

Analyze the timeline and laboratory values.

The patient experienced a

>50\%

decrease in his platelet count (from

220,000/\mu\text{L}

95,000/\mu\text{L}

) over

7

days while exposed to unfractionated heparin.

Identifying the temporal relationship between heparin exposure (

5

10

days) and significant thrombocytopenia (

>50\%

drop) is required to clinically suspect Heparin-Induced Thrombocytopenia (HIT).

Correlate laboratory findings with the clinical presentation.

The patient presents with a new right popliteal deep venous thrombosis (DVT) concurrently with the thrombocytopenia.

HIT is a highly prothrombotic state (Type 2 HIT). The presence of a new arterial or venous thrombosis confirms the severe clinical consequence of the antibody-mediated platelet activation.

Determine the immediate therapeutic intervention.

All heparin products must be stopped immediately, and a non-heparin anticoagulant must be initiated to treat the acute thrombosis.

Continuing heparin fuels the underlying pathophysiology, while an alternative fast-acting anticoagulant (like argatroban) is essential to prevent extension of the DVT and fatal complications like pulmonary embolism.

Anahtar Kavram

Patients who develop a >50% drop in platelets or new thrombosis 5-10 days after heparin exposure likely have Heparin-Induced Thrombocytopenia (HIT). Management requires immediate cessation of all heparin products (including LMWH) and initiation of a non-heparin anticoagulant like argatroban, bivalirudin, or fondaparinux.

Tahmini Süre:1m 30s

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

Sık Yapılan Hatalar

Konular

Bu konudan daha fazla soru