Quantitative EEG correlations with brain glucose metabolic rate during anesthesia in volunteers.
BACKGROUND
To help elucidate the relationship between anesthetic-induced changes in the electroencephalogram (EEG) and the concurrent cerebral metabolic changes caused by anesthesia, positron emission tomography data of cerebral metabolism obtained in volunteers during anesthesia were correlated retrospectively with various concurrently measured EEG descriptors.


METHODS
Volunteers underwent functional brain imaging using the 18fluorodeoxyglucose technique; one scan always assessed awake-baseline cerebral metabolism (n = 7), and the other scans assessed metabolism during propofol sedation (n = 4), propofol anesthesia (n = 4), or isoflurane anesthesia (n = 5). The EEG was recorded continuously during metabolism assessment using a frontal-mastoid montage. Power spectrum variables, median frequency, 95% spectral edge, and bispectral index (BIS) values subsequently were correlated with the percentage of absolute cerebral metabolic reduction (PACMR) of glucose utilization caused by anesthesia.


RESULTS
The percentage of absolute cerebral metabolic reduction, evident during anesthesia, trended median frequency (r = -0.46, P = 0.11), and the spectral edge (r = -0.52, P = 0.07), and correlated with anesthetic type (r = -0.70, P < 0.05), relative beta power (r = -0.60, P < 0.05), total power (r = 0.71,P < 0.01), and bispectral index (r = -0.81,P < 0.001). After controlling for anesthetic type, only bispectral index (r = 0.40, P = 0.08) and alpha power (r = 0.37, P = 0.10) approached significance for explaining residual percentage of absolute cerebral metabolic reduction prediction error.


CONCLUSIONS
Some EEG descriptors correlated linearly with the magnitude of the cerebral metabolic reduction caused by propofol and isoflurane anesthesia. These data suggest that a physiologic link exists between the EEG and cerebral metabolism during anesthesia that is mathematically quantifiable.
University of California-Irvine Medical Center, Department of Anesthesiology, Orange 92668, USA. MAlkire@uci.edu
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Alkire
D000328:Adult; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation; D001921:Brain / Q000000981:diagnostic imaging; D001923:Brain Chemistry / Q000187:drug effects*; D004569:Electroencephalography / Q000187:drug effects*; D005462:Fluorine Radioisotopes; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008297:Male; D015742:Propofol; D012044:Regression Analysis; D012189:Retrospective Studies; D014055:Tomography, Emission-Computed
D018685:Anesthetics, Inhalation; D005462:Fluorine Radioisotopes; D005947:Glucose; D015742:Propofol