2. Analgesia Nociception Index (ANI) index The PhysioDoloris monitor attached to the IV pole will be connected with a cable to the anesthesia monitor. We will measure and record ANI index values at the following painful events: placement of breathing tube, skin incision, initial surgical instruments insertion and muscle relaxation assessment with a twitch monitor (60mA, 100Hz, 30sec). The anesthesiologist will be blinded to ANI index values that will only be collected for research purposes. The measurements will start 5 minutes prior to the administration of general anesthesia and will continue until 5 min. after initial surgical instruments insertion.