Index computed in real time from Auditory Evoked Potentials have been described parallel to depth of anesthesia. The goal of the study was to compare general anesthesia guided on Auditory Evoked Potentials monitoring to standrad practice in order to assess if AEP monitoring can improve recovery delay (main criteria) or intraoperative hemodynamic stability (secondary criteria). Patients were randomized in 2 groups, stratified by center. Group I : AEP guided anesthesia, Group II: Blind AEP record, standard practice.

Inclusion Criteria:

• ASA status I-II patients
• aged 18 - 65 years
• scheduled for general surgery (except laparoscopic interventions) lasting longer than 1 hour.

Exclusion Criteria:

• Body weight < 70% or > 150% ideal body weight
• neurological disorder and hearing disorders (being not able to communicate with the patient in a normal tone)
• use of any medication interfering with pharmacological effect of the study including alcohol misuse or drugs.