title: Nonlinear changes in brain dynamics during emergence from sevoflurane anesthesia: preliminary exploration using new software.
abstract: BACKGROUND
  New software was used during a pilot study of nonlinear changes in the electroencephalogram during emergence from sevoflurane anesthesia.
  
  
  METHODS
  Digitized electroencephalographic signals were recorded from bipolar forehead electrodes between 1.2 and 40 k s/sec. Trajectories derived from underlying attractors were displayed continuously, and attractor dimensions were estimated. Observations are reported from 13 patients emerging from sevoflurane anesthesia.
  
  
  RESULTS
  Qualitative observations and quantitative analysis of the data demonstrated four dynamical stages during emergence from deep anesthesia to consciousness.
  
  
  CONCLUSIONS
  The dynamical stages of emergence from sevoflurane anesthesia into consciousness demonstrate a classic route toward chaos, but the presence of chaos in the conscious state remains unproven. These stages are apparent both pictorially and analytically. Pre-emergent attractor patterns are usually distinctive; their real-time display could be a useful adjunct to depth of anesthesia monitors because they may provide warning of an imminent return to consciousness.
authors.affiliation: Department of Anesthesia and Pain Management, University of Texas Southwestern Medical Center, Dallas, Texas, USA. quailrf@airmail.net
authors.forename: Peter T
authors.initials: PT
authors.lastname: Walling
authors.forename: Kenneth N
authors.initials: KN
authors.lastname: Hicks
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000627:therapeutic use*; D001921:Brain / Q000187:drug effects* / Q000502:physiology*; D003243:Consciousness; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000627:therapeutic use*; D008875:Middle Aged; D008959:Models, Neurological; D017711:Nonlinear Dynamics; D010865:Pilot Projects; D000077149:Sevoflurane; D012984:Software
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane