- Study plan: Patients will sign their informed consent during the V0 visit (preoperative). During V0, HF and LF (ECGs parameters) will be measured as well as the VAS-estimated pain. These results, medical history, concomitant diseases and medications will be reported in a case report form (CRF). The second and last visit, V1, takes place 1 hour after the patient wakes up, in the postoperative period. ECGs and VAS evaluation will be achieved in the same manner as the V0 visit. The only difference is that the measurements will be repeated to obtain a total of 5 data couples over 2 hours. These Intrapatient estimations will be used to improve statistical ECGs vs VAS correlation analysis.