Graphic 2. Distribution (%) according Biespectral analysis (BIS). BIS interval values: ≤39 (less than 40) an unnecessary too depth anesthesia, 40 to 50 as excellent depth anesthesia target with very low awareness possibility, 51 until 60 as a good depth anesthesia with low possibility of awareness and finally 61 to 70 light level of anesthesia with risk of awareness.