Somatosensory evoked potential (SSEP) monitoring is planned during posterior spinal instrumentation for scoliosis correction. Which anaesthetic technique will produce the LEAST suppression of cortical SSEP amplitudes?

• A Isoflurane at 1.2 MAC combined with nitrous oxide
• B Nitrous oxide 66% with fentanyl boluses
• C Sevoflurane at 1.5 MAC in oxygen
• D Propofol infusion with remifentanil infusion ✓

Explanation

Volatile anaesthetic agents suppress cortical SSEPs in a dose dependent fashion, increasing latency and reducing amplitude, and nitrous oxide adds further depression. A total intravenous technique based on propofol with an opioid such as remifentanil preserves SSEP amplitude and latency far better and is the standard approach for spine surgery with evoked potential monitoring. Muscle relaxants affect myogenic responses but not the cortically recorded sensory pathways used here.

Reference: Miller's Anesthesia, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.