Propofol reduces the amplitude of transcranial electrical motor-evoked potential without affecting spinal motor neurons: a prospective, single-arm, interventional study.
PURPOSE
Propofol inhibits the amplitudes of transcranial electrical motor-evoked potentials (TCE-MEP) in a dose-dependent manner. However, the mechanisms of this effect remain unknown. Hence, we investigated the spinal mechanisms of the inhibitory effect of propofol on TCE-MEP amplitudes by evaluating evoked electromyograms (H-reflex and F-wave) under general anesthesia.


METHODS
We conducted a prospective, single-arm, interventional study including 15 patients scheduled for spine surgery under general anesthesia. Evoked electromyograms of the soleus muscle and TCE-MEPs were measured at three propofol concentrations using target-controlled infusion (TCI: 2.0, 3.0, and 4.0 µg/mL). The primary outcome measure was the left H-reflex amplitude during TCI of 4.0- compared to 2.0-µg/mL propofol administration.


RESULTS
The median [interquartile range] amplitudes of the left H-reflex were 4.71 [3.42-6.60] and 5.6 [4.17-7.46] in the 4.0- and 2.0-μg/mL TCI groups (p = 0.4, Friedman test), respectively. There were no significant differences in the amplitudes of the right H-reflex and the bilateral F-wave among these groups. However, the TCE-MEP amplitudes significantly decreased with increased propofol concentrations (p < 0.001, Friedman test).


CONCLUSION
Propofol did not affect the amplitudes of the H-reflex and the F-wave, whereas TCE-MEP amplitudes were reduced at higher propofol concentrations. These results suggested that propofol can suppress the TCE-MEP amplitude by inhibiting the supraspinal motor pathways more strongly than the excitability of the motor neurons in the spinal cord.
['Deguchi|Hiroyuki|H|', 'Furutani|Kenta|K|http://orcid.org/0000-0002-1893-4384', 'Mitsuma|Yusuke|Y|', 'Kamiya|Yoshinori|Y|', 'Baba|Hiroshi|H|']
D019054:Evoked Potentials, Motor D006801:Humans D016343:Monitoring, Intraoperative D009046:Motor Neurons D015742:Propofol D011446:Prospective Studies
Propofol Motor-evoked potential Evoked electromyogram General anesthesia Intraoperative monitoring