Colorectal surgery is a common surgical operation in clinic, and general anaesthesia is often used during the operation. As the surgery is a traumatic operation, the body will produce a series of stress reactions, leading to postoperative gastrointestinal adverse reactions such as abdominal pain and vomiting, which are not conducive to postoperative rehabilitation. Especially in elderly patients, with the increase of age, there are more basic diseases, coupled with the deterioration of the physiological function of the organs, which reduces the rate of drug metabolism and promotes the body's sensitivity to anaesthetic drugs. Residual drugs will affect the function of the central nervous system, leading to reduced respiratory function, delayed recovery and cognitive dysfunction and other related complications. 1,2 The occurrence of cognitive dysfunction will prolong the hospital stay of elderly