There is a large intra-and interindividual variability in the effect of propofol. To deal with this problem, a real-time monitoring and therefore a more accurate titration of anesthetic agents is proposed. Brain function monitors based on a processed analysis of EEG (Electroencephalogram) can help to control pharmacodynamic effects of hypnotic agents. PSI values provide a measurement of the hypnotic effect of propofol. It will be observed an inverse correlation between the propofol infusion rate and the PSI value.