ABSTRACT
BACKGROUND: The dose-related effects of intravenous infusion of propofol on the rat EEG were evaluated quantitatively by spectral analysis of EEG recorded from the rat skull. METHODS: Propofol was infused into femoral vein at various concentrations ranging from 0 to 400 g/g body weight, and bipolar EEG was recorded from the rat skull and its spectrum were calculated by power spectrum analysis. The EEG electrodes were fixed at the right and left frontal, parieatal, and occipital bone on rat stereotaxic table. The density of each spectral bands(delta 1 3.25, theta 3.5 7.75, alpha 8 12.75, beta 13 31.75 Hz), total power density, median power frquency, and spectral edge frequency were derived from the spectra. RESULTS: In visual inspection of conventional EEG, low doses of propofol(100, 200 g/100 g) showed no significant changes except appearance of high frequency waves, but higher doses of propofol(300, 400 g/100 g) showed high amplitude with low frequency wave. In quantitative spectral analysis of EEG, low dose of propofol revealed no significant change except appearance of beta-waves in the frontal lobe especially. Significant EEG changes were identified during infusion of higher dose of propofol. 300 and 400 g/g of propofol revealed high amplitude and low frequency waves. Median power frequency and spectral edge frequency were significantly changed at 300 and 400 g/g of propofol in range 4.2Hz and 3.8Hz, and 12.4 Hz and 10.2 Hz respectively. CONCLUSIONS: Taken together, these findings suggest that analysis of EEG parameters derived from EEG power spectrum could be applied to determine the depth of propofol anesthesia in rats.