Postoperative pain is a reaction of the body after being stimulated by surgical injury (tissue damage), including a series of physiological, psychological and behavioral reactions. For a long time, the domestic medical profession and patients have great misconceptions about it, believing that postoperative pain is a natural phenomenon, inevitable and can only be endured; or only postoperative pain is understood as incisional pain and only the psychological feeling of discomfort or uncomfortable exists. Together with the misconceptions and excessive fears of medical and nursing staff and patients about narcotic analgesics, this important issue of postoperative analgesia, which obviously affects patients’ postoperative recovery, has been neglected. Postoperative pain and its stress response will bring adverse reactions to several aspects of the organism and directly affect postoperative recovery. The pathophysiological changes in the body caused by postoperative pain should not be taken lightly. It not only causes changes in the circulatory, respiratory, digestive, endocrine, immune and coagulation systems, but also severe pain can cause mental trauma, which can bring about anxiety, fear, insomnia and a sense of helplessness. These alterations are closely related to postoperative complications and have a significant negative impact on the prognosis of the surgery. It should also be emphasized that the tissue damage caused by surgery is not limited to the skin, but muscles and visceral organs can be involved. The source of postoperative pain, including dual agitation of somatic and visceral nerves, is obviously inaccurate to understand postoperative pain as incisional pain. Postoperative analgesia can eliminate or reduce pain and discomfort, eliminate these adverse reactions, reduce complications, promote postoperative recovery, improve postoperative quality of life, and enable you to pass the perioperative period in a painless and relaxed state, which not only implies the humane spirit of medical technology, but also has extremely important physiological significance. Clinical significance of postoperative analgesia: 1. Eliminate or reduce patient pain and discomfort, making medical technology more humane. 2. 2. Reduce anxiety, fear and insomnia caused by pain, and help recovery. 3. Reduce various complications (1) Pulmonary complications: prevent pulmonary atelectasis and pulmonary infection – because, a. effective analgesia can improve the patient’s respiratory amplitude and keep the alveoli inflated; b. prompt the patient to cough and sputum. (2) Cardiovascular complications: a. venous tethering – effective analgesia prompts patients to get out of bed early to promote venous blood return and reduce the occurrence of deep venous tethering; b. cardiovascular accidents – effective analgesia reduces the strong cardiovascular stress response triggered by pain, while reducing pain and anxiety and improving sleep. (3) Better use of abdominal pressure to help urination; help patients improve their position to facilitate urination. (4) By reducing complications and accelerating recovery. (5) Potential to reduce the occurrence of certain chronic pain. Traditional analgesic methods, especially for acute pain, are usually administered when needed (PRN), which is actually a post-pain measure with obvious drawbacks: it is difficult to administer drugs in a timely manner, and it is also difficult to administer drugs continuously, and it is more difficult to overcome individual differences in patients’ analgesic drugs, so its uniform administration often results in incomplete analgesia or overdose, which makes it difficult to ensure analgesic effects and has a greater risk of The incidence of complications and adverse reactions is significantly higher. Then, the patient can control the actual and speed (number of times) of drug administration according to his own analgesic needs, i.e., patient-controlled analgesia, and achieve the realm of on-demand drug administration.