 Several methods based on the electroencephalogram have been tested to avoid these problems, but the results have been disappointing so far. A relatively new method of processed EEG is Entropy. Entropy is a non-linear statistic parameter which describes the order of random repetitive signals. In patients it translates the anesthesia-induced calmer, more synchronized EEG into a single parameter. Spectral entropy can reproducibly indicate the hypnotic effects of propofol, thiopental and different anesthetic gases. The most popular method of processed EEG for assessment of sedation is the bispectral index BIS-Index. While BIS has been tested and validated for the use in the operation room with different anesthetics, data on its use in the ICU setting at less deep levels of sedation are controversial. The multiple concomitant medications and heterogeneity of underlying pathologies present a further challenge to the use of neuromonitoring in the ICU. 