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A Comparative Study of Stimulation Modes (Constant Current and Constant Voltage) in Motor Evoked Potential Monitoring During Orthopedic Surgery

Basic Information

Recruitment status	Pending
Health condition(s) or Problem(s) studied	Spinal Diseases
Date of first enrollment	25/12/2025
Target sample size	66
Countries of recruitment
Study type	Interventional
Intervention(s)	Neuromuscular blockade is reversed to achieve a TOF count of 4 and a TOF ratio of 100%. Stimulation settings are as follows. Monophasic waveform, pulse width of 0.5 ms, interstimulus interval of 2.0 to 4.0 ms, and a train of 4 to 6 pulses.Stimulation intensity is set at 1 to 200 mA for constant current mode and 1 to 500 V for constant voltage mode. A amplitude of 20 to 50 microV or greater is defined as the stimulation threshold. To avoid threshold bias caused by the Wedensky effect, a crossover design is employed in which the order of constant current and constant voltage stimulation is alternated between patients.

Outcome(s)

Primary Outcome	Difference in stimulation thresholds of the abductor pollicis brevis (APB) during MEP monitoring Difference in stimulation thresholds of the abductor hallucis (AH) during MEP monitoring
Secondary Outcome	Amplitude of APB and AH MEPs at an effective current of 200 mA Electrode impedance MEP acquisition rate Depth of anesthesia (BIS value)

Key inclusion & exclusion criteria

Age minimum	>= 20age old
Age maximum	Not applicable
Gender	Both
Include criteria	Target patients: Individuals undergoing orthopedic surgery under general anesthesia with TES-MEP monitoring Target age: 20 years or older
Exclude criteria	Patients in whom appropriate MEP monitoring cannot be performed after electrode placement (e.g., insufficient muscle responses to electrical stimulation, poor reproducibility, etc.) Patients deemed unsuitable for participation in this study by the operating surgeon, attending anesthesiologist, principal investigator, or co-investigators