title: EEG spectral entropy, heart rate, photoplethysmography and motor responses to skin incision during sevoflurane anaesthesia.
abstract: BACKGROUND
  Analgesia is a part of balanced anaesthesia, but direct indicators of nociception do not exist. We examined the relationship between motor reactions and physiological variables during skin incision in sevoflurane anaesthesia and hypothesized that nociception could be detected and graded by significant changes in these variables.
  
  
  METHODS
  Thirty-one women scheduled for abdominal hysterectomy participated in the study. Anaesthesia was induced with fentanyl (1 microg kg(-1)), propofol (1 mg kg(-1)) and sevoflurane. Skin incision was performed 14 min after induction during 1.6% end-tidal sevoflurane anaesthesia without neuromuscular blockade. Electrocardiography (ECG), photoplethysmography (PPG) and electroencephalography (EEG) were registered, and a range of variables was computed from these signals. The postincision values, normalized with respect to their preincision values, of movers vs. non-movers were compared. The variables showing significant differences between movers and non-movers were used to develop a logistic regression equation for the classification of patients into movers or non-movers.
  
  
  RESULTS
  Twenty-six patients were eligible for analysis, and 12 (46%) displayed a motor reaction to skin incision (movers). Many ECG, PPG and EEG-related variables showed significant differences between the pre- and postincision periods. The best classification performance, assessed by leave-one-out cross-validation, between movers and non-movers was achieved with the combination of response entropy of EEG, RR-interval and PPG notch amplitude. The corresponding equation yielded 96% correct classification with 90% sensitivity and 100% specificity. The classification performance of any single variable alone was considerably worse.
  
  
  CONCLUSIONS
  Combination of information from different sources may be required for monitoring the adequacy of analgesia during anaesthesia.
authors.affiliation: Department of Anaesthesia and Intensive Care, Helsinki University Hospital, Helsinki, Finland. elina.seitsonen@hus.fi
authors.forename: E R J
authors.initials: ER
authors.lastname: Seitsonen
authors.forename: I K J
authors.initials: IK
authors.lastname: Korhonen
authors.forename: M J
authors.initials: MJ
authors.lastname: van Gils
authors.forename: M
authors.initials: M
authors.lastname: Huiku
authors.forename: J M P
authors.initials: JM
authors.lastname: Lötjönen
authors.forename: K T
authors.initials: KT
authors.lastname: Korttila
authors.forename: A M
authors.initials: AM
authors.lastname: Yli-Hankala
mesh_terms: D000328:Adult; D018685:Anesthetics, Inhalation / Q000627:therapeutic use*; D062109:Dermatologic Surgical Procedures; D004562:Electrocardiography / Q000379:methods; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007044:Hysterectomy / Q000379:methods; D008738:Methyl Ethers / Q000627:therapeutic use*; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D009068:Movement / Q000187:drug effects*; D017156:Photoplethysmography / Q000379:methods; D000077149:Sevoflurane; D012815:Signal Processing, Computer-Assisted; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane