Objective To observe the effect and safety of the application of pressure gradient stockings (CS) alone or in combination with intermittent inflation device (IPC) for the prevention of postoperative lower limb deep vein thrombosis (DVT) in patients undergoing major surgery, and to observe the changes in coagulation and fibrinolytic activity before and after surgery. Methods Two hundred and forty patients were consecutively enrolled in radical surgery for malignant tumors in thoracic, urological, and hepatobiliary surgery, and were divided into the control group, CS-only group, CS + IPC full application group, and CS + IPC postoperative application group respectively according to the order of enrollment, with 60 cases in each group. The site of thrombosis (thigh or calf) was recorded by ultrasound examination of both lower limbs within 3-8 days after surgery. 15 patients in the CS+IPC group and 15 patients in the control group had venous blood collected before surgery, at 2h and 24h after excision for the determination of D-dimer (D-D), fibrinogen activator antigen (tPA-Ag), fibrinogen activator inhibitor (PAI), and vasopressor. inhibitor (PAI), vascular hemophilia factor (vWF), prothrombin time (PT), and activated partial thromboplastin time (APTT). The incidence of DVT by ultrasound at 3-8 days postoperatively was 15%, 23.3% and 30% in the CS + IPC full application group, CS + IPC postoperative application group and CS alone group, respectively, compared with 49.3% in the control group. 1 patient in the CS group had proximal DVT and the rest had distal DVT. There were significant differences in comparison with patients without thrombosis. In the CS+IPC group, D-D and vWF were significantly higher than those in the control group at 2 h of skin incision, and tPA-Ag was significantly lower than that in the control group; there was no difference in PAI between the two groups. Conclusion The CS+IPC full application group and CS+IPC postoperative application group could effectively reduce postoperative DVT, and the prevention effect was best in the CS+IPC full application group. Application of CS alone may be suitable for surgical patients at intermediate or sub-intermediate risk of DVT. The incidence of DVT increased with increasing age, bed rest and number of risk factors. The changes in coagulation fibrinolytic indexes in the CS+IPC total application group suggest that IPC may increase fibrinolytic activity. Data and methods Case selection: types of surgery included patients with thoracic surgery (lung cancer, esophageal cancer, etc.), urology (including kidney cancer, ureteral cancer, prostate cancer, bladder cancer, etc.) and hepatobiliary surgery (liver cancer, gallbladder cancer, pancreatic cancer and bile duct exploration, etc.) ASAI~IV grade. Exclusion criteria: Patients who are on preoperative heparin or oral warfarin anticoagulation therapy and those younger than 40 years of age. Documented concomitant risk factors: advanced age (>60 years), hypertension, hyperlipidemia, diabetes mellitus, smoking, prolonged braking, paralysis, history of venous thromboembolism, family history of thromboembolism, tumor, obesity, varicose veins, myocardial infarction, congestive heart failure, ischemic stroke, transient ischemic attack, heparin-induced thrombocytopenia, cancer chemotherapy, nephrotic syndrome, inflammatory bowel disease (ulcerative colitis, etc.), oral contraceptives and estrogen application. (low risk: less than 40 years old without additional risk factors minor surgery; intermediate risk: minor surgery with additional risk factors; 40 to 60 years old without additional risk factors non-major surgery; less than 40 years old without additional risk factors major surgery; high risk: age > 60 years old without additional risk factors non-major surgery; > 40 years old with additional risk factors major surgery; very high risk: > 40 years old plus prior (Major surgery with thromboembolism, malignancy or hypercoagulable state; orthopedic surgery of the lower extremities, pelvic fractures and spinal cord injury, etc.) Anesthesia methods and monitoring: Patients were routinely admitted to the room with an open vein and intravenous imipramine 1-2 mg. Direct arterial pressure, pulse oximetry (SPO2), partial pressure of end-expiratory carbon dioxide (PETCO2) and electrocardiogram (ECG) monitoring were monitored. An epidural puncture tube was placed for intraoperative anesthesia and postoperative pain relief. Anesthesia was induced with isoproterenol 1~2mg/kg or etomidate 0.2~0.3mg/kg, fentanyl 0.1~0.2mg, vecuronium bromide 0.06~0.1mg/kg or rocuronium bromide 0.6mg/kg for rapid induction and tracheal tube intubation. Intraoperative isoflurane, nitrous oxide, epidural anesthesia and inotropic agents were used to maintain anesthesia. All patients were given epidural self-administered analgesia (PCEA) or intravenous self-administered analgesia (PCA) for three days postoperatively. Grouping and treatment: 240 eligible patients were consecutively enrolled and divided into the control group (C), the CS-only group, the CS + IPC full application group (started preoperatively), and the CS + IPC postoperative application group, respectively, according to the order of enrollment, with 60 patients in each group.CS (TCD gradient pressure antithrombotic stocking) and IPC (SCD RESPONSE pressure antithrombotic pump) were provided by Tyco Medical, U.S.A. CS Group: After patients were admitted, the circumference of thigh root was measured (A), such as A£63.5CM selected leg-length elastic socks; then the circumference of the thickest part of the lower leg was measured ( B), B£30.5cm selected small size, 30.5cm