Postoperative pain stimulates the autonomic nervous system, induces the production of pro-inflammatory substances, reduces patient mobility and impairs vital functions. The ECG spectral analysis (ECGs) is a non-invasive marker of the autonomic nervous system state. To our knowledge, the correlation between the sympathovagal activity quantified by a non invasive method and the postoperative pain, has not been studied before.

• Principal Objective : 1)To quantify postoperative pain by the ECGs technique. 2) To compare the ECGs parameters with the visual analog pain scale (VAS) results.
• Secondary Objective : To determine the influence of preoperative chronic pain and pathophysiological profiles on the correlation between postoperative ECGs and VAS.
• Study design : An observational, prospective, single arm, single center study.
• Inclusion criteria : ¨Patients over 18 years old scheduled for surgery under general anesthesia. Patients capable of using the visual analog pain scale.
• Exclusion criteria : Pregnancy or breast feeding, impossibility to obtain an informed consent, incapacity to follow all the study schedule. Patient not protected by social security, patient likely to present hypovolemia or severe hemodynamic instability. Patient with a dysautonomia characterized by orthostatic hypotension, patients with cardiac disarrhythmias, likely to interfere with the ECG and/or the spectral analysis of ECG.
• 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.
• Number of subjects : 100

Inclusion Criteria:

• Patients over 18 years old scheduled for surgery under general anesthesia.
• Patient able to use the visual analog pain scale

Exclusion Criteria:

• Pregnancy or breast feeding
• Impossibility to obtain an informed consent
• Incapacity to follow all the study schedule
• Patient not protected by social security
• Patient likely to present hypovolemia or severe hemodynamic instability
• Patient with a dysautonomia characterized by orthostatic hypotension
• Patient with cardiac disarrhythmias, likely to interfere with the ECG and/or the spectral analysis of ECG