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Difficulty: MediumHematology and Oncology

A 68-year-old man is evaluated on postoperative day 6 following a sigmoid colectomy for colon adenocarcinoma. He reports sudden-onset shortness of breath and right-sided pleuritic chest pain. His past medical history includes chronic obstructive pulmonary disease and hypertension. His medications include subcutaneous unfractionated heparin, which was started on postoperative day 1. Temperature is 37.8°C (100.0°F), blood pressure is 128/82 mm Hg, pulse is 114/min, and respiratory rate is 24/min. Pulse oximetry is 90% on room air. Physical examination reveals decreased breath sounds at the right lung base and a swollen, tender right calf. Laboratory studies show:

Hemoglobin: 11.5 g/dL
Leukocyte count: 9,800/mm³
Platelet count: 52,000/mm³ (baseline was 260,000/mm³ prior to surgery)
Creatinine: 1.2 mg/dL

Arterial blood gas on room air:
pH: 7.32
PaCO2: 28 mm Hg
PaO2: 60 mm Hg
HCO3-: 14 mEq/L

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

  1. Discontinue unfractionated heparin and initiate a direct thrombin inhibitorAnswer
  2. B
    Measure serum D-dimer to confirm the diagnosis of pulmonary embolism
  3. C
    Administer intravenous furosemide and inhaled ipratropium-albuterol
  4. D
    Obtain blood cultures and initiate empiric broad-spectrum antibiotics
  5. E
    Administer intravenous sodium bicarbonate for inadequate respiratory compensation

Answer

Discontinue unfractionated heparin and initiate a direct thrombin inhibitor.
The patient is presenting with Heparin-Induced Thrombocytopenia (HIT) Type 2, defined by a precipitous drop in platelets (typically >50%>50\%) occurring 5 to 10 days after the initiation of heparin, frequently complicated by arterial or venous thrombosis. The swollen calf and pleuritic chest pain indicate a deep vein thrombosis and subsequent pulmonary embolism. The definitive and immediate next step in management is the absolute cessation of all heparin products and the prompt initiation of a non-heparin anticoagulant, primarily a direct thrombin inhibitor (e.g., argatroban) or fondaparinux, to prevent further thrombotic catastrophes.

Step-by-Step Solution

1
Analyze the patient's symptom onset, medication timeline, and complete blood count.
The patient experienced a >50%>50\% decline in platelets exactly 5 days after starting unfractionated heparin, accompanied by signs of new thrombosis (DVT and PE).
These findings fulfill the '4 Ts' criteria, making Heparin-Induced Thrombocytopenia (HIT) Type 2 highly probable.
2
Assess the arterial blood gas results to evaluate respiratory and metabolic status.
pH 7.32 and HCO3- 14 mEq/L indicate primary metabolic acidosis. Winter's formula (1.5×14+8=291.5 \times 14 + 8 = 29) shows the PaCO2 of 28 mm Hg is a perfect respiratory compensation.
Verifying acid-base compensation ensures no secondary hidden acid-base disturbances require emergent separate interventions.
3
Determine the optimal immediate pharmacological intervention.
Discontinue all heparin products immediately and start a non-heparin anticoagulant like a direct thrombin inhibitor (argatroban or bivalirudin).
Continued heparin exposure in HIT fuels catastrophic thrombosis, and simply stopping heparin is inadequate due to the highly prothrombotic state.

Key Concept

Heparin-Induced Thrombocytopenia (HIT) Type 2
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Topics

Hematology and Oncology

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