title: Progressive electroencephalogram frequency deceleration despite constant depth of propofol-induced sedation.
abstract: OBJECTIVE
  To investigate a possible time-dependent effect of propofol sedation on electroencephalographic activity, we analyzed the electroencephalogram frequency behavior while keeping patients at a constant level of sedation.
  
  
  METHODS
  Prospective, controlled trial.
  
  
  METHODS
  Intensive care unit of a university hospital.
  
  
  METHODS
  Twenty patients without neurologic or metabolic disorders.
  
  
  RESULTS
  During sedation with propofol (1-4 mg x kg(-1) x hr(-1)), a bifrontally recorded processed electroencephalogram was obtained. For 48 hrs, sedation was kept constant at a level according to Ramsay Scale 3 while we adjusted the dosage of propofol given per hour. At hours 6, 18, 30, and 42, blood samples were taken to assess the plasma concentration of propofol. The electroencephalogram values of 60 mins obtained during 1 hr before blood sampling were taken for further calculation. From the data, relative band power of the beta-, alpha-, theta, and delta-bands, spectral median frequency, and spectral edge frequency 90 and 95 were computed. For statistical analysis, a polynomial three-factorial repeated-measures analysis of variance with covariates was performed. Relative power of beta- and alpha-wavebands showed a constant and significant decrease over time (beta, 15.5%, 10.3%, 10.3%, 7.6%; alpha, 14.8%, 13.4%, 10.0%, 8.3%), whereas relative delta power increased (delta, 56.4%, 63.4%, 70.7%, 72.3%). The theta-waveband remained unchanged. Accordingly, spectral edge frequency 90 and 95 and spectral median frequency decreased significantly. From hours 6 to 18, a significant increase of the plasma propofol concentration was found. Subsequently, the level remained constant.
  
  
  CONCLUSIONS
  Despite constant sedation, a longer period of propofol application induces a time-dependent electroencephalogram frequency deceleration. The use of electroencephalogram derivatives to monitor depth of sedation in the intensive care unit thus should be regarded cautiously.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital of the Technical University of Dreden, Germany. theilen@rcs.tu-dresden.de
authors.forename: Hermann J
authors.initials: HJ
authors.lastname: Theilen
authors.forename: Sigrid
authors.initials: S
authors.lastname: Adam
authors.forename: Eberhard
authors.initials: E
authors.lastname: Kuhlisch
authors.forename: Michael D
authors.initials: MD
authors.lastname: Albrecht
authors.forename: Maximilian
authors.initials: M
authors.lastname: Ragaller
mesh_terms: D000328:Adult; D000777:Anesthetics; D016292:Procedural Sedation; D003654:Deceleration; D004569:Electroencephalography / Q000379:methods; D005283:Fentanyl / Q000008:administration & dosage; D005858:Germany; D006801:Humans; D008875:Middle Aged; D015742:Propofol; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000777:Anesthetics; D005283:Fentanyl; D015742:Propofol