Examkin

Question

Difficulty: MediumHematology and Oncology

While recovering on postoperative day 6 following a coronary artery bypass graft, a 62-year-old male develops acute-onset right calf pain. His postoperative course had been previously uncomplicated, and he has been receiving subcutaneous unfractionated heparin for deep vein thrombosis prophylaxis.

Vital signs show a temperature of 37.1°C (98.8°F), heart rate of 94/min, blood pressure of 132/82 mm Hg, and respiratory rate of 16/min. Physical examination reveals a swollen, tender, and mildly erythematous right calf. The right calf circumference is 4 cm greater than the left.

Laboratory studies are obtained and reveal the following:

Laboratory TestResultReference Range
Hemoglobin11.4 g/dL13.5-17.5 g/dL
Leukocytes8,200/mm³4,500-11,000/mm³
Platelets85,000/mm³150,000-400,000/mm³
Prothrombin time (PT)12 sec11-15 sec
Partial thromboplastin time (PTT)28 sec25-40 sec

A review of the patient's medical record shows a baseline platelet count of 220,000/mm³ on the day of admission.

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

  1. Discontinue unfractionated heparin and initiate argatroban infusionAnswer
  2. B
    Discontinue unfractionated heparin and initiate oral warfarin
  3. C
    Continue unfractionated heparin and obtain a lower extremity venous duplex ultrasound
  4. D
    Discontinue unfractionated heparin and transfuse one unit of apheresis platelets
  5. E
    Continue unfractionated heparin and administer intravenous cefazolin

Answer

Discontinue unfractionated heparin and initiate argatroban infusion
The correct answer involves immediately discontinuing all heparin products and starting a non-heparin anticoagulant, such as a direct thrombin inhibitor (argatroban, bivalirudin) or fondaparinux. This patient presents with a classic picture of Heparin-Induced Thrombocytopenia (HIT) type 2. HIT is an immune-mediated disorder caused by IgG antibodies against platelet factor 4 (PF4) complexed with heparin. These antibodies activate platelets, leading to widespread thrombosis and consumptive thrombocytopenia. The '4Ts' score is used to assess clinical probability: Thrombocytopenia (platelet drop >50%>50\%), Timing (typically 55 to 1010 days after heparin exposure), Thrombosis (new DVT, PE, or arterial clot), and oTher causes of thrombocytopenia not evident. This patient has a platelet count that decreased from 220,000/mm3220,000/mm^3 to 85,000/mm385,000/mm^3 (a drop of ≈61%\approx 61\%), onset on day 6, and a new suspected DVT, yielding a high probability score. When the 4T score is intermediate or high, heparin must be stopped immediately, and a non-heparin anticoagulant must be started prior to waiting for laboratory confirmation (e.g., PF4-heparin ELISA or serotonin release assay).

Step-by-Step Solution

1
Calculate the 4T score to determine the pretest probability of Heparin-Induced Thrombocytopenia (HIT).
The patient scores 6 points (High probability).
Thrombocytopenia (>50%>50\% drop) gives 2 points, Timing (day 6) gives 2 points, and Thrombosis (suspected DVT) gives 2 points.
2
Determine the immediate management for high-probability HIT.
All heparin products must be stopped, and a non-heparin anticoagulant must be started.
HIT is a highly prothrombotic state. Continuing heparin worsens the condition, and simply stopping it without alternative anticoagulation leaves the patient at high risk for fatal thrombosis.

Key Concept

Heparin-Induced Thrombocytopenia (HIT) Management
Estimated Time:1m 30s
Rate this question

Topics

Hematology and Oncology

More questions from this topic