title: [Fractal dimension--a new EEG-based method of assessing the depth of anaesthesia].
abstract: BACKGROUND
  It has been suggested that analysis of the EEG signal using the fractal dimension method may be useful for assessment of depth of anaesthesia.
  
  
  METHODS
  Thirty ASA I and II patients, scheduled for elective surgery under general anaesthesia were induced with midazolam, fentanyl and propofol and paralyzed with rocuronium or cis-atracurium. Clinical signs of the depth of anaesthesia were classified to one of five OAA/S levels. Standard vital parameters were observed and brain electrical activity was measured using the bispectral index (BIS) and burst suppression ratio (BSR). The EEG signal was recorded and processed postoperatively to calculate Higuchi's fractal dimension (FD). The latter was presented as a derivative: (D(F)-1) x 100.
  
  
  RESULTS
  Mean correlation coefficients between OAA/S scale levels, and BIS and (D(F)-1) x 100 values, were respectively: 0.749+/-0.172 and 0.753+/-0.220. In 28 (93.3%) patients, BIS correlated well with FD (r=0.63+/-0.33). In twenty cases, burst suppression occurred and the correlation coefficient between BIS and DF was much lower (r=0.5860+/-3650), when compared to the group of 10 patients in which no burst suppression was detected (r=0.711+/-0.251). Appropriate correction was made using the following formula: D(FK)=D(F)-(D(F) x BSR). The mean correlation coefficient between BIS values and D(FK) in the BS group was r=0.629+/-0.331. In all cases, the mean correlation coefficient between (D(F)-1) x 100 and BIS was r=0.661+/-0.307 (p<0.001).
  
  
  CONCLUSIONS
  The fractal dimension method can be regarded as equal to BIS for assessment of depth of anaesthesia.
authors.affiliation: Oddział Kliniczny Anestezjologii i Intensywnej Terapii SUM w Katowicach. anestitsos@sum.edu.pl
authors.forename: Monika
authors.initials: M
authors.lastname: Willand
authors.forename: Robert
authors.initials: R
authors.lastname: Rudner
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Olejarczyk
authors.forename: Magdalena
authors.initials: M
authors.lastname: Wartak
authors.forename: Radosław
authors.initials: R
authors.lastname: Marciniak
authors.forename: Michał
authors.initials: M
authors.lastname: Stasiowski
authors.forename: Tomasz
authors.initials: T
authors.lastname: Byrczek
authors.forename: Przemysław
authors.initials: P
authors.lastname: Jałowiecki
mesh_terms: D000328:Adult; D000732:Androstanols; D000768:Anesthesia, General; D018686:Anesthetics, Intravenous; D001279:Atracurium; D017558:Elective Surgical Procedures; D004569:Electroencephalography; D005260:Female; D005283:Fentanyl; D017709:Fractals; D006801:Humans; D008297:Male; D008874:Midazolam; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D003473:Neuromuscular Nondepolarizing Agents; D011237:Predictive Value of Tests; D015742:Propofol; D011446:Prospective Studies; D015203:Reproducibility of Results; D000077123:Rocuronium; D012815:Signal Processing, Computer-Assisted
chemical_list: D000732:Androstanols; D018686:Anesthetics, Intravenous; D003473:Neuromuscular Nondepolarizing Agents; D001279:Atracurium; D008874:Midazolam; D005283:Fentanyl; D000077123:Rocuronium; D015742:Propofol