Examkin

Question

Difficulty: HardPharmacologic Interventions

Six days following a two-vessel coronary artery bypass grafting, a 64-year-old male alerts the nursing staff to acute, severe pain and swelling in his right leg. His postoperative course had previously been uncomplicated. His current medication regimen includes aspirin, atorvastatin, metoprolol succinate, and subcutaneous unfractionated heparin for deep venous thrombosis prophylaxis. Vital signs show a temperature of 37.1°C, blood pressure of 128/78 mm Hg, heart rate of 82/min, and respiratory rate of 16/min. Physical examination demonstrates significant asymmetric right calf swelling with pitting edema, localized erythema, and tenderness to palpation.

Relevant laboratory results are compared to his preoperative baseline:

Laboratory TestPreoperativeCurrent (Day 6)
Hemoglobin14.2 g/dL12.1 g/dL
Platelet count245,000/mm³68,000/mm³
Serum creatinine0.9 mg/dL1.0 mg/dL

A duplex ultrasound of the lower extremities reveals an acute noncompressible thrombus in the right popliteal vein. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

  1. Discontinue unfractionated heparin and initiate argatrobanAnswer
  2. B
    Discontinue unfractionated heparin and initiate enoxaparin
  3. C
    Discontinue unfractionated heparin and initiate warfarin
  4. D
    Continue unfractionated heparin and transfuse platelets
  5. E
    Discontinue unfractionated heparin without initiating further anticoagulation

Answer

The most appropriate next step is to discontinue unfractionated heparin and initiate a direct thrombin inhibitor, such as argatroban.
This patient presents with a classic presentation of Type 2 Heparin-Induced Thrombocytopenia (HIT), defined by an unexplained drop in platelet count of >50% occurring 5 to 10 days after the initiation of heparin therapy, accompanied by a new thrombotic event (deep vein thrombosis). HIT is driven by IgG antibodies against heparin-platelet factor 4 (PF4) complexes, which activate platelets and create a profoundly prothrombotic state. The absolute first step in pharmacologic management is to discontinue all sources of heparin (including heparin flushes). Because the patient has an active thrombosis and is highly hypercoagulable, alternative systemic anticoagulation must be initiated immediately. Direct thrombin inhibitors (such as argatroban or bivalirudin) or the factor Xa inhibitor fondaparinux are the treatments of choice.

Step-by-Step Solution

1
Interpret the clinical timeline and laboratory values.
The patient experienced a >50% drop in platelet count (from 245,000/mm³ to 68,000/mm³) occurring exactly 6 days after exposure to unfractionated heparin.
Timing and magnitude of the platelet drop are key criteria (4Ts score) for identifying suspected Heparin-Induced Thrombocytopenia (HIT).
2
Assess the new clinical symptoms.
The patient developed a new DVT in the right lower extremity.
HIT is a paradoxically prothrombotic state. The formation of a new clot confirms Heparin-Induced Thrombocytopenia and Thrombosis (HITT).
3
Select the appropriate pharmacologic intervention.
All heparin products must be stopped, and a non-heparin anticoagulant (argatroban, bivalirudin, or fondaparinux) must be initiated.
Ongoing anticoagulation is mandatory due to the acute DVT. Standard agents like LMWH (cross-reactivity) and warfarin (venous gangrene risk) are contraindicated.

Key Concept

Management of Heparin-Induced Thrombocytopenia (HIT) requires the immediate discontinuation of all heparin products and the initiation of a non-heparin anticoagulant (e.g., argatroban) to manage the profoundly hypercoagulable state.
Rate this question

Topics

Pharmacologic Interventions

More questions from this topic