Prediction of responses to various stimuli during sedation: a comparison of three EEG variables.
OBJECTIVE
To compare the ability of the aepEX, a derivative of auditory evoked potentials, the bispectral index, and SEF95% to predict responses to various stimuli.


METHODS
Prospective clinical study.


METHODS
General Intensive Care Unit in a university hospital.


METHODS
Forty postsurgical, mechanically ventilated patients.


METHODS
Target concentrations of blood propofol were randomly set at 0.5 microg/ml, 1.0 microg/ml, 1.5 microg/ml, and 2.0 microg/ml, with a fixed fentanyl infusion rate between 0.5 microg.kg(-1).h(-1) and 1.5 microg.kg(-1).h(-1).


METHODS
Depth of sedation was subjectively assessed with the Ramsay Sedation Score. The aepEX was recorded using an auditory evoked potentials system. The bispectral index and SEF95% were measured using an Aspect A-1000 monitor.


RESULTS
The aepEX, bispectral index, and SEF95% correlated with the Ramsay Sedation Score, the Pk value being greatest for the aepEX, followed by the bispectral index. All three variables could predict opening of the eyes in response to verbal commands or a glabellar tap, the aepEX being a better predictor than the bispectral index or SEF95%. All three EEG variables had Pk values >0.5 in predicting coughing or movement in response to tracheal suction, but they were unable to predict increases in heart rate or systolic blood pressure.


CONCLUSIONS
The aepEX was the best predictor, followed by bispectral index. Although in most intensive care patients subjective sedation scales are sufficient to assess levels of sedation, the aepEX and bispectral index were potential alternatives to subjective scales when they do not work well in the setting of neuromuscular blockade or may not be sufficiently sensitive to evaluate very deep sedation.
Doi
Matsuyuki
M
Department of Anesthesiology and Intensive Care, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan. matdoi@hama-med.ac.jp
Morita
Koji
K
Mantzaridis
Haralambos
H
Sato
Shigehito
S
Kenny
Gavin N C
GN
D000328:Adult; D000368:Aged; D018686:Anesthetics, Intravenous; D016292:Procedural Sedation / Q000145:classification*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D005260:Female; D005283:Fentanyl; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015742:Propofol / Q000097:blood*
D018686:Anesthetics, Intravenous; D005283:Fentanyl; D015742:Propofol