Low-Dose Rocuronium Maintenance During Spine Surgery With Intraoperative Neurophysiological Monitoring

Intraoperative neurophysiological monitoring is commonly used during complex spine surgery to help detect early neurological injury. Motor evoked potentials are particularly sensitive to neuromuscular blockade. Avoiding maintenance neuromuscular blockade may improve motor evoked potential signal quality, but may increase the risk of unwanted patient movement and suboptimal surgical field conditions. Conversely, low-dose rocuronium maintenance may improve surgical conditions, but may reduce motor evoked potential amplitude if neuromuscular blockade is excessive.

This trial will evaluate whether low-dose rocuronium maintenance, titrated by quantitative neuromuscular monitoring, can preserve intraoperative neurophysiological monitoring quality while improving surgical field conditions compared with discontinuation of rocuronium after induction.

All participants will receive standardized total intravenous anesthesia with propofol-based maintenance, bispectral index monitoring, quantitative train-of-four monitoring, and intraoperative neurophysiological monitoring. Rocuronium will be administered for tracheal intubation in both groups. In the low-dose maintenance group, rocuronium will be titrated to maintain a train-of-four ratio from 0.60 to less than 0.90. In the no-maintenance group, no additional rocuronium will be given after induction unless predefined safety rescue is required.

The primary outcome will be intraoperative motor evoked potential signal quality, including mean motor evoked potential amplitude. Secondary outcomes will include successful motor evoked potential recording, motor evoked potential warning events, somatosensory evoked potential stability, surgical field condition, unwanted patient movement, time to emergence, time to extubation, early postoperative respiratory events, and new postoperative neurological deficits.

Inclusion criteria

• 1. Patients aged 18 years or older. 2. Patients scheduled for spine surgery under general anesthesia. 3. Patients undergoing spine surgery with intraoperative neurophysiological monitoring, including motor evoked potentials and/or somatosensory evoked potentials.

• Patients who agree to participate in the study and provide written informed consent.

Exclusion criteria

• 1. Pre-existing central or peripheral neurological disease that may affect intraoperative neurophysiological monitoring, such as quadriplegia, persistent sensory disorder, sequelae of stroke, or polyneuropathy.

• History of epilepsy or electroencephalographic disorder. 3. Use of neuropsychiatric drugs, strong sedatives, or drugs affecting neuromuscular or neurological conduction within 48 hours before surgery.

• Decompensated cardiovascular disease or severe respiratory disease that may affect emergence or anesthetic drug metabolism.

• Contraindication to intraoperative neurophysiological monitoring. 6. Contraindication to rocuronium. 7. Refusal to participate or withdrawal of consent at any time..