1.Pulmonary embolism Pulmonary embolism is a pathologic process caused by obstruction of the pulmonary artery or its branches by emboli. It has a low diagnosis rate, high misdiagnosis rate and high morbidity and mortality rate. According to the literature, 650,000 people suffer from pulmonary embolism in the United States each year, and 240,000 people die of pulmonary embolism. British statistics annual occurrence of non-fatal pulmonary embolism 40,000 people, due to pulmonary embolism death of hospitalized patients about 20,000 people. Some scholars believe that 80% to 90% of pulmonary embolism embolus from the lower extremity deep vein thrombosis, especially in the process of thrombolytic therapy embolus dislodgement chances are higher, the large embolus can lead to the patient’s death in a few minutes. The mortality rate of pulmonary embolism due to iliofemoral vein thrombosis has been reported to be as high as 20% to 30%. Typical symptoms of pulmonary embolism are dyspnea, chest pain, cough, and hemoptysis. The three major signs are pulmonary rales, hypertonic second tone in the pulmonary valve area, and gallop rhythm. Therefore, prevention of pulmonary embolism is more important than treatment. Currently, vena cava filter placement is used to prevent pulmonary embolism in clinical practice. Inferior vena cava filter is a device made of metal wire, which is placed into the inferior vena cava through a special delivery device to intercept the larger thrombus in the blood flow and avoid entering the pulmonary artery with the blood flow, resulting in fatal pulmonary embolism. However, the placement of filters can lead to complications such as filter displacement, obstruction, bleeding, etc., and the cost is high, so the clinical indications should be strictly controlled. Placement of filters can be considered in the following cases: ① anticoagulation is contraindicated in DVT or there are serious bleeding complications from anticoagulation. ② anticoagulation treatment still have pulmonary embolism. ③Arterial thrombectomy or pulmonary artery thrombus endarterectomy. ④ Residual DVT after the first pulmonary embolism. ⑤ Extensive large iliofemoral vein thrombosis. The route of inferior vena cava filter placement should be chosen from the healthy side, and if bilateral iliofemoral vein thrombosis, it should be chosen to be placed through the right internal jugular vein. Bleeding The most important complication of thrombolytic therapy is bleeding. Especially should be alert to gastrointestinal tract, intracranial hemorrhage. Therefore, before thrombolytic therapy should check the blood type, hemoglobin, platelets and coagulation function; the adjustment of drug dosage is usually 2~2.5 times of the normal value of the prothrombin time (PT) and partial thromboplastin time (APTT). The process of thrombolysis and after thrombolysis should closely observe the patient for bleeding tendency, such as vascular puncture points, skin, gums and other parts. Observe whether there is naked eye hematuria and microscopic hematuria, abdominal pain, black stool, etc.; if there is bleeding from the puncture site, it can be pressed to stop bleeding. Severe hemorrhage should be terminated with thrombolysis and treated symptomatically with blood or plasma transfusion. For hemorrhagic complications, patients should be instructed in self-observation and prevention. Such as bleeding gums, nasal bleeding, bleeding skin and mucous membranes, black stools, etc. Patients should not use hard, sharp objects to pick teeth, digging nostrils, ear canals, do not cough so as not to cause hemoptysis; use soft-bristled toothbrush to brush the teeth, and move gently, so as not to cause unnecessary trauma; the diet should be light and easy to digest, so as not to food damage to the digestive tract, and many times fiber-rich foods to keep the stools unobstructed. Post-thrombotic syndrome is the most common and important complication. During the process of thrombus mechanization, the venous valves are damaged or even disappeared or adhered to the wall of the tube, resulting in secondary deep venous valve insufficiency, i.e. post-thrombotic syndrome. Post-thrombotic syndrome occurs months to years after the formation of lower extremity DVT, and is mainly characterized by chronic edema, pain, muscle fatigue (venous claudication), varicose veins, hyperpigmentation, fibrous changes in subcutaneous tissues, and in severe cases, the formation of localized ulcers, which affects the patient’s quality of life. It has been reported that patients with lower extremity deep vein thrombosis who follow medical advice, wear compression stockings, take oral anticoagulant medication (e.g., aspirin 100mg/day) for three to six months, avoid prolonged standing and sedentary activities, and elevate the affected limbs during rest, generally seldom develop post-thrombotic syndrome. For patients who have developed post-thrombotic syndrome, valve repair can be used if there is valve closure insufficiency, the operation should be gentle to avoid damage to the vein. During the operation, pulse electrodes are used to stimulate the calf muscles to increase contraction and promote reflux, and after the operation, patients are encouraged to move their feet and toes actively, which has achieved satisfactory results.