During posterior fossa surgery in the sitting position, the anaesthetist notices a sudden decrease in end-tidal CO2 (ETCO2) from 35 to 22 mmHg, with a mill-wheel murmur on precordial Doppler. What is the MOST appropriate immediate management?

• A Increase tidal volume and respiratory rate to compensate for the CO2 drop
• B Administer adrenaline 1 mg IV for cardiovascular collapse
• C Flood the surgical field with saline, compress jugular veins, lower head of table, and aspirate CVP line ✓
• D Discontinue surgery immediately and place the patient supine for CT scan

Explanation

The scenario describes venous air embolism (VAE), a major hazard of sitting position neurosurgery. The sudden ETCO2 fall reflects dead-space increase from air in pulmonary vasculature; mill-wheel murmur is pathognomonic. Immediate management: (1) inform surgeon to flood/pack wound to prevent further air entry; (2) compress bilateral jugular veins to raise venous pressure; (3) lower the head (Trendelenburg) to raise venous pressure at the surgical site; (4) aspirate air via multiorifice CVP catheter; (5) discontinue N2O (expands air emboli); (6) administer 100% O2. Adrenaline is reserved for cardiovascular collapse only.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.