Venous Air Embolism — Sitting Craniotomy

About this case

A 52-year-old undergoing a posterior fossa craniotomy in the sitting position has a sudden end-tidal CO₂ crash with a mill-wheel murmur on precordial Doppler. A preoperative echocardiogram found a PFO, which the examiner included deliberately.

Key clinical features

• Massive VAE

  Precordial Doppler roar, EtCO₂ 38→10, BP 60/32 — air lock threatening RV outflow

• Durant's Maneuver

  Left lateral decubitus + Trendelenburg to move air from RV outflow — must happen in seconds

• Central Line Aspiration

  Multiorifice CVP catheter in RV — aspirate air while Durant's maneuver applied

• Paradoxical Air Embolism Risk

  Pre-op echo: PFO detected — venous air can cross to arterial circulation → stroke

What the examiner is testing

• Whether you recognise VAE quickly from the monitoring pattern rather than working through a broad differential first.
• Your knowledge of positional manoeuvres and why they must happen within seconds.
• How the pre-existing PFO changes your risk assessment and your post-event concerns.
• Your reasoning about monitoring choices for sitting-position cases before the event occurred.

Where candidates lose points

• Treating the hypotension generically without identifying the mechanism.
• Overlooking the paradoxical embolism implication of the PFO once the acute event is handled.
• Being unable to justify why this monitoring was selected for a sitting craniotomy in the first place.

How it is scored

Every BoardSim case is scored across the same five phases — pre-operative evaluation, anaesthetic plan, intra-operative management, crisis management, and emergence — for a total of 100 points, with a pass set at 70 and no missed critical action. You receive a written report against each phase rather than a single number. Read the scoring methodology.