The effect of the decreased serum concentration of propofol induced by rapid fluid infusion on the spectral edge frequency 90 and median frequency

: The effect of decreased serum concentration of propofol induced by rapid infusion therapy on the EEG was assessed by spectral edge frequency 90% (SEF90) or median frequency (MF) during propofol anesthesia. The eight scheduled surgical patients were administered propofol with a constant rate, and the rapid infusion therapy with 10 ml.kg-1 of acetate Ringer's solution significantly decreased the serum concentration of propofol from 1.96 +/- 0.22 micrograms.ml-1 to 1.68 +/- 0.19 micrograms.ml-1 (approximately 17% reduction). Simultaneous monitoring of SEF90 and MF, however, demonstrated no change during investigation. These results suggest that the mild decrease of the concentration of propofol might not induce the significant change of EEG, or that the reduction of propofol concentration by infusion might be deceptive and produce no significant change in the concentrations of each pharmacological compartment.