Moderate to severe pain from surgery and trauma can affect almost all organ functions, regardless of the location of the pain. Understanding the causes of pain and applying the appropriate analgesic medication can be extremely beneficial for recovery from surgery and trauma. The main causes of postoperative pain occurrence? (1) incisional trauma; (2) intestinal distension, intestinal spasm; (3) irritation of wound and nerve by drainage tube; (4) injury to bone, synovium and periosteum, ischemia-reperfusion injury caused by tourniquet, tissue vascular injury leading to the release of inflammatory and pain-causing substances (such as substance P, PGE, tissue ammonia, cytokines, etc.); (5) muscle spasm around trauma; (6) inflammatory reaction caused by trauma causing peripheral nerve sensitization. What kinds of drugs are commonly used for postoperative analgesia? (1) Opioids include morphine, fentanyl, dulcolax and codeine, the first three of which are strong analgesics and the latter is a weak analgesic. (2) local anesthetics commonly used local anesthetics such as bupivacaine and ropivacaine and two other long-acting local anesthetics. (3) Cyclooxygenase inhibitors The main drugs are acetaminophen (Tylenol), fenpropathrin, ketorolac, and selective cyclooxygenase 2 inhibitors (Cilobal). (4) Others: Adjuvant sedation and anxiolytic treatment In current drug therapy, it is mostly advocated to combine two or more drugs with different mechanisms of action, so that the analgesic effects are synergistic with each other while reducing the dosage of each drug, thus reducing the incidence and severity of side effects. For example, the combination of opioid and non-steroidal drugs, epidural opioid compound local anesthetics, epidural opioid compound local anesthetics with oral non-steroidal drugs, etc.