The effect of sub-anaesthetic dose of esketamine on postoperative fatigue of in patients after laparoscopic radical resection of colorectal cancer

Interventions: group K:a bolus injection of 0.1 mg/kg esketamine intravenously after anesthesia induction, followed by a continuous intravenous infusion of 0.1 mg/kg/h throughout the operation;group C:a bolus injection of 0.1 mg/kg normal saline intravenously after anesthesia induction, followed by a continuous intravenous infusion of 0.1 mg/kg/h throughout the operation Primary outcome(s): identity consequence fatigue scale Study Design: Parallel