Influence of Lidocaine Infusion on Motor Evoked Potential Thresholds

The investigators will compare the stimulation threshold for motor evoked potentials (MEPs) for patients undergoing spine surgery with intraoperative neurophysiologic monitoring (IONM) who receive a lidocaine infusion vs. normal saline (NS) infusion. The endpoint for this objective will be the final stimulation threshold for MEPs at the end of the surgery. The stimulation threshold for MEPs is a commonly used metric to determine the effects of anesthetic agents on MEP signals. Secondary objectives will somatosensory evoked potentials (SSEPs) with an endpoint of amplitude and latency of SSEPs throughout the surgery. Other secondary outcomes will include, intraoperative mean arterial pressure (MAP), intraoperative propofol consumptions, and post-operative visual analog scale (VAS) and opioid consumption.