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

• A Brachial plexus stretch injury
• B Pressure necrosis of the occiput
• C Air embolism detected by precordial Doppler or transoesophageal echocardiography ✓
• D Corneal abrasion from incomplete eye closure

Explanation

Venous air embolism (VAE) is the most characteristic complication of the sitting position in neurosurgery because the surgical site is above the level of the heart, creating negative venous pressure that entrains air when dural sinuses or emissary veins are breached. Precordial Doppler ultrasonography is the most sensitive non-invasive monitor; transoesophageal echocardiography is even more sensitive. Mill-wheel murmur, decreased ETCO2, and hypotension are late signs. A patent foramen ovale (present in ~25% of adults) poses the risk of paradoxical air embolism (arterial), which can cause stroke.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.