Entropy is more resistant to artifacts than bispectral index in brain-dead organ donors.
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.
Wennervirta
Johanna
J
Department of Anesthesiology and Intensive Care Medicine, Helsinki University Hospital, 340, 00029, Helsinki, Finland. johanna.wennervirta@hus.fi
Salmi
Tapani
T
Hynynen
Markku
M
Yli-Hankala
Arvi
A
Koivusalo
Anna-Maria
AM
Van Gils
Mark
M
Pöyhiä
Reino
R
Vakkuri
Anne
A
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