Which inhalational agent is ABSOLUTELY contraindicated in patients requiring electroencephalographic (EEG) monitoring and neuroelectrophysiological intraoperative monitoring during spinal cord surgery?

• A Sevoflurane at 0.5 MAC
• B Nitrous oxide (N₂O) at 50–70%
• C High-dose volatile agents (>1.5 MAC of any agent) combined with nitrous oxide ✓
• D Desflurane at 0.3 MAC

Explanation

Intraoperative neurophysiological monitoring (IONM) including somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) is profoundly suppressed by volatile anaesthetic agents in a dose-dependent manner. At >1.5 MAC, SSEPs and MEPs may be completely abolished, making monitoring unreliable. N₂O also suppresses evoked potentials and is typically avoided. TIVA with propofol and opioid is the preferred technique for IONM procedures. Low-dose volatile (<0.5 MAC) may be acceptable for SSEP monitoring but is generally suboptimal and avoided for MEP monitoring.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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