title: Spectral entropy for assessing the depth of propofol sedation.
abstract: BACKGROUND
  For patients in the intensive care unit (ICU) or under monitored anesthetic care (MAC), the precise monitoring of sedation depth facilitates the optimization of dosage and prevents adverse complications from underor over-sedation. For this purpose, conventional subjective sedation scales, such as the Observer's Assessment of Alertness/Sedation (OAA/S) or the Ramsay scale, have been widely utilized. Current procedures frequently disturb the patient's comfort and compromise the already well-established sedation. Therefore, reliable objective sedation scales that do not cause disturbances would be beneficial. We aimed to determine whether spectral entropy can be used as a sedation monitor as well as determine its ability to discriminate all levels of propofol-induced sedation during gradual increments of propofol dosage.
  
  
  METHODS
  In 25 healthy volunteers undergoing general anesthesia, the values of response entropy (RE) and state entropy (SE) corresponding to each OAA/S (5 to 1) were determined. The scores were then analyzed during each 0.5 mcg/ml- incremental increase of a propofol dose.
  
  
  RESULTS
  We observed a reduction of both RE and SE values that correlated with the OAA/S (correlation coefficient of 0.819 in RE-OAA/S and 0.753 in SE-OAA/S). The RE and SE values corresponding to awake (OAA/S score 5), light sedation (OAA/S 3-4) and deep sedation (OAA/S 1-2) displayed differences (P < 0.05).
  
  
  CONCLUSIONS
  The results indicate that spectral entropy can be utilized as a reliable objective monitor to determine the depth of propofol-induced sedation.
authors.affiliation: Department of Anesthesiology, National Medical Center, Seoul, Korea.
authors.forename: Mi-Young
authors.initials: MY
authors.lastname: Kwon
authors.forename: Seung-Yun
authors.initials: SY
authors.lastname: Lee
authors.forename: Tae-Yop
authors.initials: TY
authors.lastname: Kim
authors.forename: Duk Kyung
authors.initials: DK
authors.lastname: Kim
authors.forename: Kyoung-Min
authors.initials: KM
authors.lastname: Lee
authors.forename: Nam-Sik
authors.initials: NS
authors.lastname: Woo
authors.forename: Young-Jae
authors.initials: YJ
authors.lastname: Chang
authors.forename: Myung Ae
authors.initials: MA
authors.lastname: Lee