This study aims to compare total intravenous anesthetic agents: combined remimazolam and propofol vs. propofol monotherapy. The comparison parameters are intraoperative hypotension, patient's involuntary movement, neurophysiological monitoring quality, onset time, recovery time, and postoperative rescue anti-emetics requirements.

This study hypothesizes that the combination regimen of remimazolam and propofol as total intravenous anesthesia in neurosurgical procedures requiring neurophysiological monitoring can reduce the incidence of hypotension compared to propofol monotherapy while providing comparable levels of neurophysiological monitoring and surgical conditions. With this hypothesis, the study aims to compare the frequency, severity, and duration of hypotension, frequency of patient movement, and appropriateness of neurophysiological monitoring between the combination therapy of remimazolam and propofol and propofol monotherapy in total intravenous anesthesia.

Inclusion Criteria:

• Patients aged 19 and above with planned neurosurgical procedures requiring neurophysiological monitoring, classified as American Society of Anesthesiologists (ASA) physical status classification 1, 2, or 3 in the United States.

Exclusion Criteria:

1. Patients who refuse to participate in the study.
2. Patients who are pregnant or lactating.
3. Patients with hypersensitivity to the investigational drugs or to soy, peanuts, or Dextran 40.
4. Patients with acute narrow-angle glaucoma.
5. Patients with alcohol or drug dependence.
6. Patients with hepatic impairment classified as Child-Pugh class C.
7. Patients with lactose intolerance.
8. Patients requiring emergency surgery.