The objective of the study is to determine wether the use of the Bispectral Index Monitor (BIS) as a method to guide anaesthesia for children in different groups of age, undergoing ear nose and throat surgery anaesthetized with an infusion of Propofol and Remifentanil with an high dose of Remifentanil (0,5-2 mcg/kg/min), can lead to a reduction in the time needed for extubation and in the amount of anesthetics used.