The intervention will start when the anesthesiologist decide to suspend the sevorane or desflurane dial. At this moment, the fresh flow gas of the anesthesia machine will be adjusted to 7-8 liters per minute and the infusion of remifentanil will be set up to establish a Ce of 2.0 ng/ml or 2.5 ng/ml. All patients will be extubated only when all of these three parameters exist: response to name by eyes opening, response to orders of breathing and mouth opening.