A patient is positioned in the sitting (beach chair) position for posterior fossa surgery. Which unique complication is the MOST dangerous and requires specific monitoring?

• A Pressure injuries to the sacrum and heels
• B Sciatic nerve stretch from extreme hip flexion
• C Cerebral hyperperfusion from elevated head position
• D Venous air embolism (VAE), monitored with precordial Doppler and end-tidal CO₂ ✓

Explanation

The sitting position creates a surgical field above the heart, generating negative venous pressure at open veins (diploë, emissary veins, dural sinuses) which can entrain air — venous air embolism (VAE). The incidence approaches 25–45% in sitting craniotomies. VAE presents as a sudden drop in ETCO₂ (reduced lung perfusion) and a mill-wheel murmur on precordial Doppler. A patent foramen ovale converts it to paradoxical arterial embolism causing stroke. Precordial Doppler is the most sensitive non-invasive monitor; transoesophageal echocardiography is most sensitive overall. Treatment: flood field with saline, Durant's manoeuvre, aspirate through CVC.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.