Concentration 3 - 4 ng/ml Dose of infusion of remifentanil to reach a (PC) 3 - 4 ng/ml, in the following manner: The assistant placed the infusion balloon in such a way that it could not be seen by the treating anesthesiologist, he proceeded to open the corresponding wrapping according to the consecutive which corresponds to the patient. The remifentanil dose was adjusted according to the randomization: Group T = 3 - 4 ng/ml. 20 years old - 9.0 mcg/Kg/h, 30 years old - 8.5 mcg/Kg/h, 40 years old - 8.0 mcg/kg/h, 50 years old - 7.5 mcg/kg/h, 60 years old - 7.0 mcg/kg/h, 70 years old - 6.5 mcg/kg/h, 80 years old - 6.0 mcg kg/h.