• Yuri Yamamoto, Masahiko Kawaguchi, Hironobu Hayashi, Ryuichi Abe, Satoki Inoue, Hiroyuki Nakase, Toshisuke Sakaki, and Hitoshi Furuya.
• Department of Anesthesiology, Nara Medical University, Nara, Japan.
• J Neurosurg Anesthesiol. 2010 Jan 1; 22 (1): 6-10.

BackgroundRecently, we developed a new technique to augment myogenic motor evoked potentials (MEPs), called as posttetanic MEPs (p-MEPs), in which tetanic stimulation is applied to peripheral nerve before transcranial stimulation. However, the data on p-MEPs are limited. This study was conducted; (1) to evaluate the influences of repetitive use of p-MEPs on p-MEP amplitudes, (2) to evaluate the residual effects of use of p-MEPs on subsequent conventional MEPs (c-MEPs), and (3) to compare the variability of p-MEPs with that of c-MEPs.MethodsSixty patients under propofol/fentanyl anesthesia with partial neuromuscular blockade were enrolled. For p-MEP measurements, tetanic stimulation was applied to posterior tibial nerve 1 second before transcranial stimulation. In study 1, p-MEPs were repetitively recorded with intervals of 10 or 60 seconds. In study 2, the amplitudes of c-MEPs recorded 15, 30, 60, and 120 seconds after p-MEP recordings were compared with those of control. In study 3, the coefficients of variation of c-MEP and p-MEP responses were compared.ResultsThe repetitive use of p-MEP with an interval of 10 seconds, but not 60 seconds, induced a significant reduction of p-MEP amplitude. Amplitudes of c-MEP were significantly increased when applied within 60 seconds after p-MEP recordings. The coefficient of variations of p-MEPs was similar to those of c-MEPs.ConclusionsThe results indicated that the amplitudes of p-MEP and c-MEP might be affected when applied with a short interval after p-MEP recording.

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