Ciprofol and Remimazolam for Intraoperative Neurophysiological Monitoring During Spine Surgery

Intraoperative neurophysiological monitoring, including motor evoked potentials and somatosensory evoked potentials, is commonly used during spine surgery to help detect impending neurological injury. The quality of these signals can be affected by anesthetic agents. Ciprofol and remimazolam are newer intravenous hypnotic agents that may be suitable for total intravenous anesthesia during procedures requiring neurophysiological monitoring, but direct within-patient comparisons between the two agents are lacking. This single-center, prospective, randomized, two-sequence crossover trial will compare the effects of ciprofol and remimazolam, administered with remifentanil, on intraoperative MEP and SEP signal quality during spine surgery. Eligible participants will be randomized to receive either ciprofol followed by remimazolam or remimazolam followed by ciprofol during predefined stable intraoperative monitoring windows. The primary outcome is the within-participant difference in lower-extremity MEP peak-to-peak amplitude between the ciprofol and remimazolam periods. Secondary outcomes include SEP amplitude and latency, MEP latency, warning-threshold events, hemodynamic variables, rescue medication requirements, recovery characteristics, and postoperative neurological status.

Inclusion Criteria: 1. Age 18 to 75 years. 2. Scheduled to undergo elective spine surgery. 3. Planned intraoperative monitoring with MEP and SEP/SSEP. 4. Expected surgical duration sufficient to complete two study drug periods and intraoperative monitoring windows, preferably at least 3.5 to 4 hours. 5. American Society of Anesthesiologists physical status I to III. 6. Able to provide written informed consent, or consent provided by a legally authorized representative where applicable. Exclusion Criteria: 1. Known allergy or contraindication to ciprofol, remimazolam, benzodiazepines, propofol-related formulations, opioids, or relevant excipients. 2. Severe preoperative motor or sensory deficit preventing interpretable target MEP or SEP baseline recordings. 3. Implanted cardiac pacemaker, skull defect, or other condition considered unsuitable for transcranial electrical stimulation. 4. Severe neuromuscular disease, poorly controlled epilepsy, severe cognitive impairment, or inability to complete postoperative neurological assessment. 5. Severe hepatic or renal dysfunction, severe hemodynamic instability, shock, or requirement for high-dose vasoactive medications before enrollment. 6. Long-term benzodiazepine, sedative-hypnotic, antiepileptic drug use, or drug/alcohol dependence that may substantially alter anesthetic response. 7. Expected need for continuous deep neuromuscular blockade during surgery, preventing valid MEP monitoring. 8. Any other condition judged by the investigators to make participation unsuitable or unsafe.