Fat embolism syndrome after long bone fracture — FFICM MCQ

Correct answer: D — Fat embolism syndrome

The correct answer is D, fat embolism syndrome. This man has sustained a femoral shaft fracture and, 36 hours later, develops the classic triad of hypoxaemia, confusion (neurological disturbance) and a petechial rash, which are the major Gurd criteria for fat embolism syndrome (FES). FES typically presents 24 to 72 hours after long bone or pelvic fracture, when marrow fat is extruded into the venous circulation and embolises to the lungs, producing bilateral patchy infiltrates and thrombocytopenia from platelet aggregation around fat globules. A normal CTPA excluding a large thromboembolus, in the presence of this triad after skeletal trauma, is the key discriminating feature that points away from venous thromboembolism and towards FES. Why the other options are wrong: E. Transfusion-related acute lung injury: there is no history of blood product transfusion in the stem, which is a prerequisite for this diagnosis, and it does not explain the petechial rash or the temporal link to a femoral fracture. A. Aspiration pneumonia: this would typically follow a witnessed aspiration event or reduced consciousness at the time of injury, and does not account for the petechiae or thrombocytopenia seen here. C. Acute coronary syndrome: this does not produce a petechial rash, thrombocytopenia or bilateral radiographic infiltrates, and confusion with hypoxaemia in this trauma context is far better explained by a systemic embolic process. B. Tension pneumothorax: this causes acute cardiorespiratory collapse with tracheal deviation and absent breath sounds, not a subacute 36 hour course with rash and thrombocytopenia. Key point: after a long bone fracture, the triad of hypoxaemia, confusion and petechiae developing 24 to 72 hours post injury, with a normal CTPA, is characteristic of fat embolism syndrome rather than pulmonary thromboembolism.

Reference: BJA Education, Fat embolism syndrome (Luff and Hewson, 2021), Royal College of Anaesthetists, https://www.bjaed.org/article/S2058-5349(21)00053-6/fulltext