If necessary before surgery, midazolam will be administered from 0.02 to 0.05 mg / kg intravenous (IV) depending on clinical response and after the patient is set in the surgical position, if necessary, an intravenous infusion of propofol will be administered at 0.5 - 2mg / kg / h. Sedative drugs with analgesic effects as opioids, ketamine, etc, will be avoided to not interfere with the main analgesic study assessment.