title: Entropy is more resistant to artifacts than bispectral index in brain-dead organ donors.
abstract: OBJECTIVE
  To evaluate the usefulness of entropy and the bispectral index (BIS) in brain-dead subjects.
  
  
  METHODS
  A prospective, open, nonselective, observational study in the university hospital.
  
  
  METHODS
  16 brain-dead organ donors.
  
  
  METHODS
  Time-domain electroencephalography (EEG), spectral entropy of the EEG, and BIS were recorded during solid organ harvest.
  
  
  RESULTS
  State entropy differed significantly from 0 (isoelectric EEG) 28%, response entropy 29%, and BIS 68% of the total recorded time. The median values during the operation were state entropy 0.0, response entropy 0.0, and BIS 3.0. In four of 16 organ donors studied the EEG was not isoelectric, and nonreactive rhythmic activity was noted in time-domain EEG. After excluding the results from subjects with persistent residual EEG activity state entropy, response entropy, and BIS values differed from zero 17%, 18%, and 62% of the recorded time, respectively. Median values were 0.0, 0.0, and 2.0 for state entropy, response entropy, and BIS, respectively. The highest index values in entropy and BIS monitoring were recorded without neuromuscular blockade. The main sources of artifacts were electrocauterization, 50-Hz artifact, handling of the donor, ballistocardiography, electromyography, and electrocardiography.
  
  
  CONCLUSIONS
  Both entropy and BIS showed nonzero values due to artifacts after brain death diagnosis. BIS was more liable to artifacts than entropy. Neither of these indices are diagnostic tools, and care should be taken when interpreting EEG and EEG-derived indices in the evaluation of brain death.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Helsinki University Hospital, 340, 00029, Helsinki, Finland. johanna.wennervirta@hus.fi
authors.forename: Johanna
authors.initials: J
authors.lastname: Wennervirta
authors.forename: Tapani
authors.initials: T
authors.lastname: Salmi
authors.forename: Markku
authors.initials: M
authors.lastname: Hynynen
authors.forename: Arvi
authors.initials: A
authors.lastname: Yli-Hankala
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Koivusalo
authors.forename: Mark
authors.initials: M
authors.lastname: Van Gils
authors.forename: Reino
authors.initials: R
authors.lastname: Pöyhiä
authors.forename: Anne
authors.initials: A
authors.lastname: Vakkuri
mesh_terms: D016477:Artifacts; D001926:Brain Death / Q000175:diagnosis*; D004569:Electroencephalography; D004576:Electromyography; D019277:Entropy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014019:Tissue Donors