Concurrent recording of AEP, SSEP and EEG parameters during anaesthesia: a factor analysis.
BACKGROUND
Spontaneous EEG, mid-latency auditory evoked potentials (AEP) and somatosensory evoked potentials (SSEP) have been used to monitor anaesthesia. This poses the question as to whether or not EEG, AEP and SSEP vary in parallel with varying conditions during surgical anaesthesia.


METHODS
A total of 81 variables (31 EEG, 22 SSEP, 28 AEP) were simultaneously recorded in 48 surgical patients during anaesthesia. A total of 307 cases of the 81 variables in stable anaesthetic states were recorded. A factor analysis was performed for this data set.


RESULTS
Sixteen variables were excluded because of multicollinearity. We extracted 13 factors with eigenvalues >1, representing 78.3% of the total variance, from the remaining 65 x 307 matrix. The first three factors represented 12%, 11% and 10% of the total variance. Factor 1 had only significant loadings from EEG variables, factor 2 only significant loadings from AEP variables and factor 3 only significant loadings from SSEP variables.


CONCLUSIONS
EEG, AEP and SSEP measure different aspects of neural processing during anaesthesia. This gives rise to the hypothesis that simultaneous monitoring of these quantities may give additional information compared with the monitoring of each quantity alone.
Schwilden
H
H
Department of Anaesthesiology, Universität Erlangen-Nürnberg, Germany. schwilden@kfa.imed.uni-erlangen.de
Kochs
E
E
Daunderer
M
M
Jeleazcov
Ch
Ch
Scheller
B
B
Schneider
G
G
Schüttler
J
J
Schwender
D
D
Stockmanns
G
G
Pöppel
E
E
D000768:Anesthesia, General; D018686:Anesthetics, Intravenous; D003627:Data Interpretation, Statistical; D017558:Elective Surgical Procedures; D004569:Electroencephalography; D005071:Evoked Potentials; D005072:Evoked Potentials, Auditory; D005073:Evoked Potentials, Somatosensory; D005163:Factor Analysis, Statistical; D006801:Humans; D008874:Midazolam; D016343:Monitoring, Intraoperative / Q000379:methods*; D011292:Premedication; D015742:Propofol; D012815:Signal Processing, Computer-Assisted
D018686:Anesthetics, Intravenous; D008874:Midazolam; D015742:Propofol