Noxious stimuli do not modify myogenic motor evoked potentials by electrical stimulation during anesthesia with propofol-based anesthesia.
OBJECTIVE
To investigate whether motor evoked potentials (MEP) to transcranial electrical stimulation under constant blood propofol concentration are affected by the arousing effect of surgical noxious stimuli.


METHODS
Twenty patients who underwent elective spinal surgery were studied. Patients were anesthetized with 50% nitrous oxide in oxygen, fentanyl, and propofol to maintain the bispectral index (BIS) score around 50. MEP in response to a multipulse transcranial electrical stimulation at stimulus sites of C3-C4 were recorded over the right abductor pollicis brevis muscle. Changes of peak-to-peak amplitude and onset latency of MEP, BIS score before and after surgical stimuli were evaluated. Propofol plasma concentration was measured at the same time points.


RESULTS
Both MEP amplitude and latency did not change significantly after surgical stimuli although BIS increased significantly (48 +/- 6 to 58 +/- 5; P < 0.05). Plasma propofol concentration was maintained at the same level between the two measurement points (3.3 +/- 0.7 to 3.3 +/- 0.7 micro g*mL(-1)). There was no relation between BIS change and changes of MEP amplitude and latency, and propofol plasma concentration.


CONCLUSIONS
MEP to the transcranial electrical stimulation under a constant and clinically appropriate blood propofol concentration are not affected by surgical noxious stimuli.
Inoue
Satoki
S
Department of Anesthesiology and Neurosurgery, Nara Medical University, Japan. sinoue@vapop.ucsd.edu
Kawaguchi
Masahiko
M
Takahashi
Masahiro
M
Kakimoto
Meiko
M
Sakamoto
Takanori
T
Kitaguchi
Katsuyasu
K
Furuya
Hitoshi
H
Morimoto
Tetsuya
T
Sakaki
Toshisuke
T
D000768:Anesthesia, General; D018686:Anesthetics, Intravenous / Q000097:blood / Q000627:therapeutic use*; D001921:Brain / Q000502:physiology; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation; D015742:Propofol / Q000097:blood / Q000627:therapeutic use*; D013131:Spine / Q000601:surgery*; D013514:Surgical Procedures, Operative
D018686:Anesthetics, Intravenous; D015742:Propofol