Influence of Esmolol on a Closed-Loop Anesthesia System

Inclusion Criteria: * male patients scheduled for a general anesthesia Exclusion Criteria: * age lower than 18 years * allergy to propofol, or to soja or to peanuts, or to sufentanil, to remifentanil, or to morphine, or to a myorelaxant or to an excipient, * any other history of anaphylactic reaction, * hypersensibility to sufentanil, or to remifentanil, or to other derivate of fentanyl, * hypersensibility to esmolol or to an excipient, * history of central nervous system disease, * patients receiving a psychotropic treatment or an agonist-antagonist opiate, * hypovolemic patients, * patients receiving a cardio-vascular treatment, * patients with a pacemaker, * expected bleeding more than 20% of the blood volume, * simultaneous general and loco-regional anesthesia, * patients suffering from asthma, COPD, trouble of the heart rhythm or conduction, cardiac insufficiency, cardiogenogenic shock, Prinzmetal syndrome, pheochromocytoma, * patients with a heart rate less than 50/min and/or an arterial hypotension, * neurosurgical act or any other which precludes an adequate positioning of the bispectral electrode.