In the operating room, patients will be monitored, receive peripheral venoclysis and then randomized into two groups: in group I, the anesthetic induction will be done with pre oxygenation with 100% O2, propofol, cisatracurium, lidocaine and fentanyl; In group II the induction will be done with the same doses of propofol, cisatracurium, lidocaine and placebo.