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The level of consciousness of patients undergoing surgery evolves continuously as the effect of the anesthetic agents is counteracted by the surgical stimuli. The monitors of depth of anesthesia, based on the analysis of the electroencephalogram (EEG), have been progressively introduced into the daily practice to provide additional information about the state of the patient. In this work, the Index of Consciousness (IoC), a recent index which uses the information from EEG spectrum and symbolic dynamics through a fuzzy inference system, is introduced. The bispectral index BIS, a well-established index, is used to validate the IoC. A good correlation is found between both indexes. Furthermore, IoC presents a significantly higher prediction probability Pk of the level of sedation than BIS, and can thus be considered as an interesting measure of the level of consciousness.