Evaluating the Predictive Value of the Nociception Level Index NOL

"After tracheal intubation, a Tetanus test (60 mAmp,100 Hz) is done during 30 sec at remifentanil level Ce of 4 ng/ml (with starting NOL value \<10). According to the NOL response: increment of 1 ng/ml of RemiCe if NOL gradient ≥ 20 / decrement of 1 ng/ml of remifentanil Ce NOL gradient \< 10. During the testing period propofol Ce is fixed at the concentration associated with BIS levels between 45-60 during the first calibration.~Upon the incision and 2 minutes after skin incision, Propofol TCI (Schnider model) is adjusted to BIS between 45-60 and remifentanil Ce at which the variation of NOL index variation is less than10 units at a NOL starting value \<10. MAP (mean arterial pressure), HR (heart rhythm) and NIBP (non-invasive blood pressure) will be measured.~The formula derived from the calibration phase will be tested during a single tetanic stimulation at remifentanil Ce of 4 ng/ml during the validation phase."