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Venous air embolism — FRCA Final MCQ

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HardNeurosurgical AnaesthesiaVenous air embolismFRCA Final

A 47-year-old man is in the sitting position for posterior fossa surgery. The end-tidal CO2 suddenly falls from 4.8 to 2.8 kPa, oxygen saturation drops to 90%, and the surgeon reports air in the operative field. Blood pressure falls to 80/45 mmHg. What is the most likely cause of the complication?

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Correct answer: E — Venous air embolism

A sudden fall in end-tidal CO2 with hypoxaemia and hypotension during sitting posterior fossa surgery suggests venous air embolism. The surgical field provides the air-entry source above the heart. Anaphylaxis and endobronchial intubation are differentials but the operative context and abrupt capnography change make air embolism most likely. Management includes flooding the field, jugular compression where appropriate, 100% oxygen, haemodynamic support and aspiration via central line if present.

Reference: NACCS neuroanaesthesia guidance; RCoA Final FRCA Syllabus 2026