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Question 4#

A 30-year-old man is admitted to the hospital after a motorcycle accident that resulted in a fracture of the right femur. The fracture is managed with traction. Three days later the patient becomes confused and tachypneic. A petechial rash is noted over the chest. Lungs are clear to auscultation. Arterial blood gases show P O2 of 50, PCO2 of 28, and pH of 7.49. Which of the following is the most likely diagnosis? 

A) Unilateral pulmonary edema
B) Hematoma of the chest
C) Fat embolism
D) Pulmonary embolism
E) Staphylococcus aureus pneumonia

Correct Answer is C


Because clinical signs of neurologic deterioration and a petechial rash have occurred in the setting of fracture and hypoxia, fat embolism is the most likely diagnosis. This process occurs when neutral fat is introduced into the venous circulation after bone trauma or fracture. The latent period is 12 to 36 hours. A pulmonary embolus usually has a longer latent period. In addition, pulmonary embolus would not cause the petechial rash. Confusion out of proportion to the degree of hypoxemia is also seen with fat emboli. Unilateral pulmonary edema can be seen with aspiration and after rapid expansion of a pneumothorax, but not with fat embolism. Hematoma of the chest wall can occur after trauma, but does not cause hypoxemia and confusion. An early pneumonia would not be associated with a petechial rash.