Placebo_comparator: Standard Clinical Care Group

Hemodynamic changes outside of the normal range i.e., hypertension (systolic blood pressure greater than 140 mm Hg), tachycardia (heart rate greater than 90 min-1) and hypotension (mean arterial pressure less than 60 mm Hg) will be first assessed using the guidance of Bispectral index and Train of four monitors. Sufentanil in doses of 2.5 to 5 mcg (maximum of 0.6-1.2 mic/kg for the entire surgery) is administered if the Bispectral index and Train of four monitor values are within normal range and if required vasopressor infusion is used. Vasoconstrictors may be given as a continuous infusion of norepinephrine, or bolus doses of ephedrine or phenylephrine. Only when blood pressure remains, low additional crystalloids will be given. Finally, in case of bradycardia (heart rate less than 30 min-1), atropine may be given

Experimental: Nociception Level-guided Analgesia Group

In the nociception level-guided group, sufentanil will be administered to maintain a nociception level value between 10 and 25. In case the nociception level values rise greater than 25 for more than 60 s, additional 2.5 microgram sufentanil (if nociception level increase remained less than 45) or 5 micrograms (if nociception level increase greater than 45). Atropine will be administered when heart rate decreases less than 30 min-1. Because the nociception level may be sensitive to such medication, nociception level values will then not used for at least 5 min to guide analgesia, with the exception of norepinephrine as this drug will be given as continuous infusion