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Difficulty: MediumPulmonary and Critical Care

A 61-year-old woman is brought to the emergency department due to the sudden onset of severe shortness of breath and right-sided pleuritic chest pain that began 2 hours ago. She has no significant past medical history but underwent a total left hip arthroplasty 2 weeks ago. She admits to spending most of her time in bed since the surgery due to pain. Her temperature is 37.1°C (98.8°F), blood pressure is 114/72 mm Hg, pulse is 118/min, and respiratory rate is 26/min. Pulse oximetry shows 88% on room air. Physical examination reveals clear lungs bilaterally. Cardiac auscultation reveals a regular tachycardia with a prominent pulmonic component of the second heart sound. The left calf is mildly swollen and tender compared to the right. Arterial blood gas analysis on room air reveals the following:

ParameterResultReference Range
pH7.527.35–7.45
pCO2pCO_228 mm Hg35–45 mm Hg
pO2pO_254 mm Hg75–105 mm Hg
HCO3−HCO_3^-22 mEq/L22–28 mEq/L

Which of the following are the most appropriate immediate steps in the management of this patient? (Select all that apply)

  1. Initiate therapeutic anticoagulationAnswer
  2. B
    Apply Winter's formula to determine the adequacy of respiratory compensation
  3. C
    Administer a loop diuretic to reduce suspected pulmonary venous congestion
  4. Obtain computed tomography pulmonary angiographyAnswer
  5. E
    Administer empiric broad-spectrum intravenous antibiotics

Answer

The correct immediate management steps are to initiate therapeutic anticoagulation and obtain a computed tomography pulmonary angiography (CTPA).
This patient has a high clinical probability of an acute pulmonary embolism (PE), supported by her recent major orthopedic surgery, immobility, unilateral calf swelling (suggesting deep vein thrombosis), sudden-onset pleuritic chest pain, and hypoxia with clear lungs. Her arterial blood gas reveals an acute respiratory alkalosis secondary to tachypnea and hyperventilation. In a hemodynamically stable patient with a high pretest probability for PE, the most appropriate immediate steps are to initiate empiric therapeutic anticoagulation (provided there are no absolute contraindications) and to confirm the diagnosis with computed tomography pulmonary angiography (CTPA).

Step-by-Step Solution

1
Evaluate the clinical presentation and risk factors.
The patient has sudden-onset dyspnea, pleuritic chest pain, hypoxia, tachycardia, and unilateral calf swelling 2 weeks after major orthopedic surgery.
These findings yield a very high clinical probability for an acute pulmonary embolism (PE) originating from a deep vein thrombosis.
2
Analyze the arterial blood gas (ABG) results.
The ABG shows an elevated pH (7.52) and a low pCO2pCO_2 (28 mm Hg) with a normal HCO3−HCO_3^- (22 mEq/L).
This confirms an acute, uncompensated respiratory alkalosis driven by hypoxia-induced hyperventilation, a classic finding in acute PE.
3
Determine the algorithmic management for high-probability PE.
Empiric anticoagulation must be started immediately, and diagnostic imaging (CTPA) should be ordered.
In hemodynamically stable patients with high clinical suspicion for PE, anticoagulation should not be delayed while awaiting the confirmatory CT scan, provided there are no contraindications.

Key Concept

In patients with a high clinical pretest probability of acute pulmonary embolism, empiric therapeutic anticoagulation should be initiated prior to confirming the diagnosis with computed tomography pulmonary angiography.
Estimated Time:1m 30s
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Topics

Pulmonary and Critical Care

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