Evaluation of posttetanic motor evoked potentials--the influences of repetitive use, the residual effects of tetanic stimulation to peripheral nerve, and the variability.
BACKGROUND
Recently, 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.


METHODS
Sixty 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.


RESULTS
The 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.


CONCLUSIONS
The results indicated that the amplitudes of p-MEP and c-MEP might be affected when applied with a short interval after p-MEP recording.
Department of Anesthesiology, Nara Medical University, Nara, Japan.
Yuri
Y
Yamamoto
Masahiko
M
Kawaguchi
Hironobu
H
Hayashi
Ryuichi
R
Abe
Satoki
S
Inoue
Hiroyuki
H
Nakase
Toshisuke
T
Sakaki
Hitoshi
H
Furuya
D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D004558:Electric Stimulation / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005283:Fentanyl / Q000008:administration & dosage; D006801:Humans; D008297:Male; D008875:Middle Aged; D010525:Peripheral Nerves / Q000502:physiology*; D015742:Propofol / Q000008:administration & dosage; D013979:Tibial Nerve / Q000502:physiology; D013997:Time Factors
D018686:Anesthetics, Intravenous; D005283:Fentanyl; D015742:Propofol