<qa>  What is the bolus of?Participants will be randomized into one of three study groups: Group L: intravenous lidocaine: bolus of 1.5 mgkg at induction of anesthesia followed by infusion of 1 mgkgh intraoperatively and for 24 h postoperatively. Group K: Ketamine: bolus of 0.15 mgkg followed by infusion of 0.1 mgkgh intraoperatively and for 24 h postoperatively. Control Group C: an equal volume of saline. The anesthetic technique will be standardized, and the postoperative assessments included pain scores, opioid consumption, recovery of bowel function and 6-minute walk distance 6-MWD on the fourth postoperative morning. At 3 months, patients will be questioned for chronic postoperative pain using the Neuropathic Pain 4 questionnaire. 