Anesthesia Effects on Neurophysiological Monitoring Flashcards

Which inhaled anesthetic causes the GREATEST suppression of cortical evoked potentials at equivalent concentrations?

Answer: Isoflurane

Isoflurane causes greater cortical evoked potential suppression than desflurane or sevoflurane at equivalent MAC values due to its profound effect on cortical synaptic transmission.

Nitrous oxide specifically affects evoked potentials by:

Answer: Reducing amplitude of cortical responses, particularly affecting MEPs significantly

Nitrous oxide, particularly when combined with volatile agents, reduces cortical response amplitudes and has a pronounced suppressive effect on MEPs even at low concentrations.

The optimal anesthetic protocol for intraoperative neurophysiological monitoring (IONM) when MEP monitoring is required is:

Answer: Total intravenous anesthesia (TIVA) with propofol and remifentanil, avoiding NMB

TIVA with propofol and remifentanil minimizes cortical and MEP suppression while avoiding NMB that would prevent muscle CMAP recording, making it the gold standard for IONM.

How do opioids affect intraoperative evoked potentials?

Answer: They have minimal effect on SSEPs, MEPs, and BAEPs at clinical doses

Opioids at clinical doses have minimal effects on SSEPs, MEPs, and BAEPs, making them compatible with IONM and suitable as part of TIVA protocols for monitored cases.

Etomidate transiently increases SSEP amplitudes because it:

Answer: Decreases synaptic inhibition in the somatosensory cortex

Etomidate decreases cortical inhibitory activity (GABA modulation), temporarily enhancing cortical excitability and increasing SSEP amplitudes, which can be exploited therapeutically.

Ketamine's effect on intraoperative MEP monitoring is characterized by:

Answer: Relative MEP preservation or enhancement due to NMDA receptor antagonism

Ketamine's NMDA receptor antagonism tends to preserve or even enhance MEPs, making it useful as an adjuvant anesthetic when MEP monitoring is difficult.