A 35-year-old man sustains a closed femoral shaft fracture treated with intramedullary nailing. On the third postoperative day he develops acute respiratory distress, petechiae over the chest and axillae, and confusion. His PaO2 is 62 mmHg. Which pathophysiological mechanism is MOST responsible for the hypoxia?
- A Deep vein thrombosis with pulmonary thromboembolism
- B Haemothorax from rib injury at time of original trauma
- C Aspiration pneumonia from prolonged supine position
- D Fat emboli obstructing pulmonary capillaries with inflammatory lipase activation ✓
Explanation
Fat embolism syndrome (FES) classically presents 24–72 hours after long bone fracture with the triad of respiratory distress, neurological dysfunction, and petechiae. Marrow fat globules enter venous circulation and lodge in pulmonary capillaries; phospholipase A converts neutral fat to free fatty acids, causing chemical pneumonitis and capillary leak, producing non-cardiogenic pulmonary oedema distinct from DVT-PE. Petechiae—particularly over the chest, axillae, and conjunctivae—are pathognomonic and not seen in DVT-PE. Haemothorax and aspiration would present differently and lack the petechiae.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.