During posterior fossa surgery in the sitting position, what is the MOST serious feared complication and how is it best monitored?

• A Spinal cord injury; monitored by somatosensory evoked potentials
• B Tension pneumothorax; monitored by peak airway pressure
• C Air embolism; monitored by precordial Doppler ultrasound (most sensitive) and end-tidal CO2 ✓
• D Paradoxical bradycardia; monitored by continuous ECG only

Explanation

Venous air embolism (VAE) is the most serious and uniquely common complication of the sitting (beach chair) position in posterior fossa neurosurgery, as the surgical field is above the level of the heart, creating a negative venous pressure gradient that entrains air. Precordial Doppler is the most sensitive non-invasive monitor for VAE, detecting as little as 0.05 mL/kg of air. End-tidal CO2 decreases as air enters the pulmonary circulation and is a reliable monitor for haemodynamically significant VAE. A right heart catheter can aspirate entrained air. ETCO2 drop is the most practical real-time indicator intraoperatively.

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

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Written and medically reviewed by the StethoPrep medical team.