RecruitingPhase 3Drug trialEffect of Ketamine on Intraoperative Motor Evoked PotentialsThe goal of this clinical trial is to learn about the effect of ketamine on intraoperative motor evoked potentials in adult patients undergoing thoracolumbar spinal fusions. Participants will undergo a standard anesthetic. In addition to the standard anesthetic, the patients will be administered increasing doses of ketamine with motor-evoked potentials being measured at each dose, to assess any impacts.