Which of the following is incorrect about fat embolism?
A. Fat emboli occur after long bone fractures and large joint replacement. The classic fat embolism syndrome consists of progressive respiratory insufficiency, petechial rash, and altered mental status, and is estimated to occur in 0.5% to 2.0% of patients with long bone fractures.
B. The onset is usually immediate after injury.
C. The petechiae may appear about the head, neck, or axillae; in the conjunctivae; and in mucous membranes. The patient has hypoxemia, a widened P(A-a)O 2, and diffuse bilateral infiltrates on chest radiography.
D. Although corticosteroids have been used, there are no controlled studies to support their use.
Answer: B
The onset is usually 24 to 72 hours after injury.
The chest radiograph is normal in 87.5% of patients in whom the diagnosis of fat embolism is made based on lipiduria. In those with positive chest findings, widespread or patchy areas of air space consolidation are noted, due to alveolar hemorrhage and edema distributed predominantly in the peripheral and basal areas. The densities clear in 7 to 10 days but may take 4 weeks to resolve completely. Acute cor pulmonale with cardiac failure also may be seen.