title: Age-related changes in EEG power spectra in infants during sevoflurane wash-out.
abstract: BACKGROUND
  Few electroencephalography (EEG) data are available in anaesthetized infants. This study aimed to identify EEG characteristics that might warn of awakening (AW) from sevoflurane anaesthesia in infants.
  
  
  METHODS
  Twenty intubated infants [aged 39-77 weeks post-menstrual age (PMA)] were studied after surgery during sevoflurane wash-out. EEG was recorded at the end of surgery and throughout emergence. Changes in EEG time and frequency domains were described.
  
  
  RESULTS
  At the end of surgery, mean end-tidal sevoflurane concentration was 2.3% (range 1.5-3.5) before wash-out and reduced to 0.3% (0.1-0.6) when AW began. On AW, movement artifacts made signals difficult to interpret. Before awakening, most power was within frequencies ≤4 Hz, but trends over time were variable. Summated power in frequencies between 20 and 70 Hz was almost always <5 µV(2). During anaesthesia, there were two common power spectra: infants >52 weeks PMA had obvious summated power in the frequency range 5-20 Hz (P5-20 Hz) (mean 308, median 320, range 110-542 µV(2)), which decreased before awakening began [mean decrease 252 µV(2) (95% CI 153-351)], whereas younger infants had low P5-20 Hz throughout. P5-20 Hz during anaesthesia increased with age; power in this frequency band of ~100 µV(2) separated infants younger and older than 52 weeks PMA.
  
  
  CONCLUSIONS
  During sevoflurane wash-out, decreasing P5-20 Hz might warn of impending AW in infants >3 months old, but not in younger infants.
authors.affiliation: Department of Anaesthesia, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK.
authors.forename: M R J
authors.initials: MR
authors.lastname: Sury
authors.forename: A
authors.initials: A
authors.lastname: Worley
authors.forename: S G
authors.initials: SG
authors.lastname: Boyd
mesh_terms: D000375:Aging / Q000502:physiology*; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics / Q000494:pharmacology*; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008738:Methyl Ethers / Q000493:pharmacokinetics / Q000494:pharmacology*; D016343:Monitoring, Intraoperative / Q000379:methods; D000077149:Sevoflurane; D012815:Signal Processing, Computer-Assisted; D014851:Wakefulness / Q000187:drug effects
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane
keywords: anaesthesia, general; consciousness monitors; electroencephalography; infant; sevoflurane