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S. E. Brodie, D. Desiderio, D. H. Abramson; Comparison of ERG Baselines Under Anesthesia With BIS Analysis of EEG Activity. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4514.
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To identify EEG (electroencephalogram) activity as a possible source for baseline noise in the ERG (electroretinogram) signal under general anesthesia using the BIS EEG monitor.
40 patients undergoing electroretinography under general anesthesia (sevofluorane) for monitoring of retinal function during treatment for retinoblastoma, or for other diagnostic purposes, were monitored for frontal EEG activity using the BIS EEG monitor (Aspect Medical Systems). The BIS performs a proprietary bi-spectral analysis of the EEG waveform, and summarizes the EEG activity as a single numerical value between 0 (flat-line) and 100 (fully awake). Anesthesia levels were monitored by traditional clinical means, and were not adjusted by reference to BIS values. ERGs were recorded with the Espion-2 system (Diagnosys LLC) using ERG-jet contact lens electrodes. Baseline ERG records obtained in the absence of flash stimuli were de-trended. Power spectra and RMS noise estimates were obtained.
While variability was substantial, there was a significant trend to lower noise in the ERG baselines associated with lower BIS values, especially for the low-frequency components
These findings suggest that leakage of EEG electrical activity into the ERG circuit may be an important source of noise in the ERG baseline recorded under sevoflurane general anesthesia.
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