title: Effects of sevoflurane and propofol on frontal electroencephalogram power and coherence.
abstract: BACKGROUND
  The neural mechanisms of anesthetic vapors have not been studied in depth. However, modeling and experimental studies on the intravenous anesthetic propofol indicate that potentiation of γ-aminobutyric acid receptors leads to a state of thalamocortical synchrony, observed as coherent frontal alpha oscillations, associated with unconsciousness. Sevoflurane, an ether derivative, also potentiates γ-aminobutyric acid receptors. However, in humans, sevoflurane-induced coherent frontal alpha oscillations have not been well detailed.
  
  
  METHODS
  To study the electroencephalogram dynamics induced by sevoflurane, the authors identified age- and sex-matched patients in which sevoflurane (n = 30) or propofol (n = 30) was used as the sole agent for maintenance of general anesthesia during routine surgery. The authors compared the electroencephalogram signatures of sevoflurane with that of propofol using time-varying spectral and coherence methods.
  
  
  RESULTS
  Sevoflurane general anesthesia is characterized by alpha oscillations with maximum power and coherence at approximately 10 Hz, (mean ± SD; peak power, 4.3 ± 3.5 dB; peak coherence, 0.73 ± 0.1). These alpha oscillations are similar to those observed during propofol general anesthesia, which also has maximum power and coherence at approximately 10 Hz (peak power, 2.1 ± 4.3 dB; peak coherence, 0.71 ± 0.1). However, sevoflurane also exhibited a distinct theta coherence signature (peak frequency, 4.9 ± 0.6 Hz; peak coherence, 0.58 ± 0.1). Slow oscillations were observed in both cases, with no significant difference in power or coherence.
  
  
  CONCLUSIONS
  The study results indicate that sevoflurane, like propofol, induces coherent frontal alpha oscillations and slow oscillations in humans to sustain the anesthesia-induced unconscious state. These results suggest a shared molecular and systems-level mechanism for the unconscious state induced by these drugs.
authors.affiliation: From the Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts (O.A., K.J.P., A.L.S., K.E.H., E.N.B., P.L.P.); Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts (M.B.W.); Harvard Medical School, Boston, Massachusetts (O.A., E.N.B., P.L.P.); Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, Massachusetts (M.B.W., E.N.B., P.L.P.); Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts (E.N.B.); and Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts (E.N.B.).
authors.forename: Oluwaseun
authors.initials: O
authors.lastname: Akeju
authors.forename: M Brandon
authors.initials: MB
authors.lastname: Westover
authors.forename: Kara J
authors.initials: KJ
authors.lastname: Pavone
authors.forename: Aaron L
authors.initials: AL
authors.lastname: Sampson
authors.forename: Katharine E
authors.initials: KE
authors.lastname: Hartnack
authors.forename: Emery N
authors.initials: EN
authors.lastname: Brown
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Purdon
mesh_terms: D000328:Adult; D000513:Alpha Rhythm / Q000187:drug effects; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D004569:Electroencephalography / Q000187:drug effects* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D015742:Propofol / Q000494:pharmacology*; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D008738:Methyl Ethers; D000077149:Sevoflurane; D015742:Propofol