On an equi-MAC basis, which anesthetic has the greatest effect on the Motor Evoked Potentials (MEPs) of recorded muscles?

Nitrous Oxide is known to have a particularly significant impact on Motor Evoked Potentials (MEPs) when used on an equi-MAC basis among anesthetics. This effect is primarily due to its unique mechanism of action and its emphasized influence on central nervous system excitability.

Nitrous Oxide acts as a non-competitive antagonist, affecting NMDA receptors and influencing neurotransmitter release, which can lead to a more pronounced depression of motor pathways compared to the volatile anesthetics. Because of this, MEPs, which assess the integrity of motor pathways, may exhibit reduced amplitudes or altered latencies under Nitrous Oxide, indicating a greater overall effect on motor function during surgical procedures in comparison to the other inhaled anesthetics listed.

In contrast, while Isoflurane, Sevoflurane, and Desflurane also affect MEPs, they tend to do so to a lesser degree because their mechanisms may not significantly alter motor pathway excitability as markedly as Nitrous Oxide. Understanding these differences is crucial for intraoperative monitoring and management of patient care during surgeries requiring neuromonitoring.