Recently intraoperative motor evoked potential monitoring (MEP) is widely used to reduce neural damage during neurosurgery.

As neuromuscular blockade(NMB) during MEP monitoring decreases the amplitude of MEP, partial NMB is usually maintained during general anesthesia. Continuous infusion of NMB agent is preferred than bolus infusion during MEP monitoring. There are a lot of NMB agents in clinical use. But there have been no reports about the effect of changing NMB agent on efficacy of MEP monitoring.

Therefore, the investigators performed a randomized controlled trial to evaluate the effect of changing NMB agent on the variability of MEP amplitude during neurosurgery.

Recently intraoperative motor evoked potential monitoring (MEP) is widely used to reduce neural damage during neurosurgery.

As neuromuscular blockade(NMB) during MEP monitoring decreases the amplitude of MEP, partial NMB is usually maintained during general anesthesia. Continuous infusion of NMB agent is preferred than bolus infusion during MEP monitoring. There are a lot of NMB agents in clinical use. But there have been no reports about the effect of changing NMB agent on efficacy of MEP monitoring.

Therefore, the investigators performed a randomized controlled trial to evaluate the effect of changing NMB agent on the variability of MEP amplitude during neurosurgery.

Inclusion Criteria:

• Adult patients undergoing neurosurgery with intraoperative motor evoked potential monitoring

Exclusion Criteria:

• Patients who can not undergo motor evoked potential monitoring due to central or peripheral neuromuscular disease (e.g. Cerebral palsy, Myasthenia gravis, Acute spinal injury, neurologic shock)
• Patients with hepatic or renal disease with altered metabolism of vecuronium
• Patients with medication which influence the metabolism of vecuronium (e.g. calcium channel blocker, aminoglycoside antibiotics, Lithium, MgSO4)