A neurosurgeon plans resection of an arteriovenous malformation (AVM) in the eloquent cortex under general anaesthesia with neurophysiological monitoring (motor-evoked potentials, MEPs). Which anaesthetic agent combination is MOST compatible with reliable intraoperative MEP monitoring?

• A Isoflurane 1.5 MAC + 50% N2O + fentanyl infusion
• B Sevoflurane 2 MAC + midazolam + morphine PCA
• C Ketamine induction + nitrous oxide maintenance + epidural analgesia
• D Propofol TIVA + remifentanil infusion with no volatile agents ✓

Explanation

Total intravenous anaesthesia (TIVA) with propofol and remifentanil is the gold standard for intraoperative neurophysiological monitoring (IONM) of MEPs. Volatile halogenated agents suppress MEPs in a dose-dependent manner; at ≥0.5 MAC they significantly attenuate cortical and spinal responses, making interpretation unreliable. Nitrous oxide also suppresses MEPs. Propofol TIVA at usual doses allows adequate MEP signal amplitude with minimal suppression. Ketamine has excitatory CNS effects but is not used for maintenance due to prolonged recovery and ICP concerns.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.