title: Effects of propofol, etomidate, midazolam, and fentanyl on motor evoked responses to transcranial electrical or magnetic stimulation in humans.
abstract: The effects of propofol, etomidate, midazolam, and fentanyl on motor evoked responses to transcranial stimulation (tc-MERs) were studied in five healthy human volunteers. Each subject, in four separate sessions, received intravenous bolus doses of propofol 2 mg.kg-1, etomidate 0.3 mg.kg-1, midazolam 0.05 mg.kg-1, and fentanyl 3 micrograms.kg-1. Electrical tc-MERs (tce-MERs) were elicited with anodal stimuli of 500-700 V. Magnetic tc-MERs (tcmag-MERs) were elicited using a Cadwell MES-10 magnetic stimulator at maximum output. Compound muscle action potentials were recorded from the tibialis anterior muscle. Duplicate tce-MERs and tcmag-MERs were recorded before and up to 30 min after drug injection. Reproducible baseline tce-MERs (amplitude 4.7 +/- 0.43 (SEM) mV, latency 29.4 +/- 0.35 ms) and tcmag-MERs (amplitude 3.7 +/- 0.43 mV, latency 31.1 +/- 0.39 ms) were obtained in all subjects. Pronounced depression of tce-MER amplitude to 2% of baseline values (P less than 0.01) was observed 2 min after injection of propofol. Thirty minutes after injection of propofol, amplitude depression to 44% of baseline (P less than 0.05) was still present, despite an apparent lack of sedation. Midazolam caused significant (P less than 0.01) amplitude depression, e.g., tcmag-MER to 16% of baseline values 5 min after injection. Significant depression persisted throughout the 30-min study period. Fentanyl did not cause any statistically significant amplitude changes in this small population. Etomidate caused significant but transient depression of tc-MER amplitude. However, there was considerable intersubject variability. Latency did not change significantly after any drug.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: University of California, San Diego.
authors.forename: C J
authors.initials: CJ
authors.lastname: Kalkman
authors.forename: J C
authors.initials: JC
authors.lastname: Drummond
authors.forename: A A
authors.initials: AA
authors.lastname: Ribberink
authors.forename: P M
authors.initials: PM
authors.lastname: Patel
authors.forename: T
authors.initials: T
authors.lastname: Sano
authors.forename: R G
authors.initials: RG
authors.lastname: Bickford
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D005045:Etomidate / Q000494:pharmacology*; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D005283:Fentanyl / Q000494:pharmacology*; D006801:Humans; D007275:Injections, Intravenous; D008280:Magnetics; D008297:Male; D008874:Midazolam / Q000494:pharmacology*; D009132:Muscles / Q000187:drug effects*; D015742:Propofol / Q000494:pharmacology*
chemical_list: D008874:Midazolam; D005283:Fentanyl; D015742:Propofol; D005045:Etomidate