Fat Embolism Syndrome — FRCA Final MCQ

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ModerateTrauma & Emergency AnaesthesiaFat Embolism SyndromeFRCA Final

A 70-year-old woman sustains a femoral shaft fracture and pelvic fracture in a road traffic collision. Thirty-six hours after reamed intramedullary fixation of the femur, she develops worsening hypoxaemia, tachycardia and new confusion. A non-blanching petechial rash is present over her upper chest and conjunctivae. What is the most likely diagnosis?

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Correct answer: A — Fat embolism syndrome

The correct answer is fat embolism syndrome. The delayed onset after long-bone trauma and intramedullary instrumentation, together with hypoxaemia, neurological disturbance and an upper-body/conjunctival petechial rash, is the classical pattern. Marrow fat produces pulmonary microvascular obstruction and an inflammatory endothelial injury, causing ventilation–perfusion mismatch, cerebral dysfunction and dermal capillary petechiae. Pulmonary thromboembolism may cause hypoxaemia and tachycardia but does not explain the characteristic rash. Bone cement implantation syndrome occurs around femoral canal instrumentation, cementation or prosthesis insertion and causes acute hypoxia and cardiovascular compromise, not this delayed triad. Air embolism is usually abrupt and procedure-related. Anaphylaxis more typically causes urticaria, flushing, angioedema or bronchospasm rather than petechiae. Treatment of fat embolism syndrome is supportive, including oxygenation, ventilation and haemodynamic support.

Reference: Royal College of Anaesthetists. Guide to the FRCA Examination, Fat embolism syndrome, question 171 and explanatory answer. 2026. https://www.rcoa.ac.uk/media/49226