The Modulatory Effects of Anesthetics and Analgesics on Neurophysiological Monitoring and Underlying Mechanisms

Intraoperative Neurophysiological Monitoring (IONM) is an indispensable surgical tool that offers invaluable insights into neurological function across a spectrum of anatomical areas. By comprehensively assessing the integrity of the brain, brainstem, spinal cord, cranial nerves, and peripheral nerves, IONM plays a pivotal role in guiding surgical decision-making and optimizing patient outcomes, particularly in the context of high-risk procedures. Intraoperative drugs, especially anesthetics and/or analgesics, differentially modulate neurophysiological monitoring, which remarkably affects the application of neurophysiological monitoring under specific conditions and indicates the neurobiological mechanisms of anesthetics/analgesics. This review will describe various neurophysiological modalities utilized in intraoperative procedures, each employing a wide variety of physiological principles; summarize the modulatory effects of anesthetics/analgesics on these neurophysiological monitoring parameters; and elucidate their underlying mechanisms, with a particular emphasis on evoked potentials. Insights gleaned from this review can inform strategies of anesthesia management for surgeries that require IONM and guide future investigations on the mechanisms of anesthesia/analgesia.