A Multicenter, Randomized, Double-Blind, Placebo-Controlled Trial of Intravenous Ibuprofen 400 and 800 mg Every 6 Hours in the Management of Postoperative Pain.

Inclusion Criteria: * Enrollment was open to patients undergoing scheduled abdominal surgery (intestinal or lower abdomen) or orthopedic surgery (such as knee arthroplasty or shoulder joint reconstruction) under general anesthesia with endotracheal intubation and were expected to require patient-controlled intravenous analgesia (PCIA) pump for more than 24h for moderate to severe pain after surgery. Exclusion Criteria: * Those who can not understand the NRS score and cooperate with the evaluation; those who had head trauma or complicated with organic lesions of the central nervous system within 4 weeks before operation; those who developed coagulation dysfunction or took anticoagulants and antiplatelet drugs; those with a history of severe cardio-cerebrovascular disease, heart failure; those with liver and kidney dysfunction, severe endocrine system diseases, mental illness; those with a history of peptic ulcer or bleeding; those who did not control grade 2 or above hypertension or were still taking two or more of antihypertensive drugs such as angiotensin converting enzyme inhibitors (ACEI), angiotensin converting enzyme antagonists (ARB) and diuretics at admission; Increased toxicity due to the interaction of methotrexate, lithium preparations, etc. with the test drug; use of NSAIDs or analgesic muscle relaxants within 24 hours before operation, narcotic dependence or tolerance; allergy to ibuprofen or other NSAIDs; pregnant or lactating women