Inclusion Criteria:  Adults ≥ 18 years and younger than 80 years Patients able to comprehend, sign, and date the written informed consent document to participate in the clinical trial. ASA Class I, II, III classified by the anesthesiologist. Patients planned for a surgical procedure under general anesthesia.  Exclusion Criteria:  Patients having epidural analgesia infused by a pain pump during the operation. Patients with chronic pain or getting medication used for chronic pain, like anti-epileptics, antidepressants, opioids. Pregnant women (asked at the patient before the operation) Patients with electrically sensitive life support systems (e.g. implanted pacemaker, defibrillator)