High-frequency Stimulation Restored Motor-evoked Potentials to the Baseline Level in the Upper Extremities but Not in the Lower Extremities Under Sevoflurane Anesthesia in Spine Surgery

Journal of Neurosurgical Anesthesiology , 03/21/2012

Shida Y et al. – Sevoflurane is inadvisable for motor–evoked potentials (MEPs) monitoring in the legs during spine surgery as modulation of the transcranial electrical stimulation (TES) frequency did not eliminate the suppressive effect of sevoflurane on the MEPs in the legs. Clinicians should be forewarned of the greater risk of unmonitorable MEPs, especially in the legs, under sevoflurane anesthesia.


  • The effects of sevoflurane and propofol and modulation of the stimulation frequencies on MEPs elicited by TES in the anterior tibial, abductor hallucis, and abductor pollicic brevis muscles were investigated in 31 patients undergoing spine surgery.
  • MEPs elicited by transcranial magnetic stimulation were also obtained before the surgeries and compared with the TES MEPs.


  • Sevoflurane attenuated the MEP amplitudes significantly.
  • The MEP amplitudes increased with the TES frequency in the case of the arms, but not the legs, under sevoflurane anesthesia.
  • The MEPs recorded under propofol anesthesia did not differ from those elicited by transcranial magnetic stimulation before the surgery (control).

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