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Difficulty: MediumOrthopedic Surgery

A 22-year-old man is evaluated in the trauma intensive care unit for acute-onset respiratory distress and altered mental status. Twenty hours ago, he was involved in a motorcycle collision, sustaining a closed, comminuted fracture of the right femoral shaft and a nondisplaced fracture of the left radius. He was initially hemodynamically stabilized, splinted, and placed in skeletal traction while awaiting definitive surgical fixation. His current temperature is 37.9°C (100.2°F), blood pressure is 112/68 mm Hg, pulse is 126/min, and respiratory rate is 28/min. Pulse oximetry reveals an oxygen saturation of 86% on room air. Physical examination demonstrates scattered, non-blanching erythematous macules over the anterior chest and axillae. Lung auscultation reveals bilateral diffuse crackles. Neurologic examination shows a restless and confused patient without focal motor or sensory deficits. Which of the following is the most likely diagnosis?

  1. Fat embolism syndromeAnswer
  2. B
    Pulmonary thromboembolism
  3. C
    Hospital-acquired pneumonia
  4. D
    Sepsis-induced acute respiratory distress syndrome
  5. E
    Traumatic subdural hematoma

Answer

The correct answer is fat embolism syndrome.
The correct answer describes a condition that classically presents with a triad of respiratory distress, neurologic abnormalities, and a petechial rash in patients who have recently sustained long bone or pelvic fractures. The marrow fat enters the venous circulation, leading to both mechanical obstruction of pulmonary capillaries and a systemic inflammatory response, typically manifesting 12 to 72 hours post-injury.

Step-by-Step Solution

1
Analyze the patient's initial injury and timeline.
The patient sustained a comminuted long bone fracture (femur) and is 20 hours post-injury.
Identifying the mechanism and timing of injury narrows the differential diagnosis for severe post-trauma complications.
2
Evaluate the new-onset clinical signs and symptoms.
The patient developed a triad of respiratory distress (hypoxia, tachypnea), neurologic dysfunction (confusion, restlessness), and a petechial rash over the chest and axillae.
Recognizing this specific combination of findings is essential for pinpointing the underlying systemic etiology.
3
Synthesize the findings to establish the diagnosis.
The combination of a recent long bone fracture and the classic triad of symptoms confirms the diagnosis.
Disruption of the bone marrow releases fat globules into the systemic circulation, which classically triggers this specific syndrome within 12 to 72 hours of injury.

Key Concept

Fat embolism syndrome typically presents with the classic triad of respiratory distress, neurologic abnormalities, and a petechial rash within 12 to 72 hours following a severe long bone or pelvic fracture.
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Orthopedic Surgery

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