Elderly pulmonary embolism

　　The etiology and pathophysiology of pulmonary embolism can roughly be included in three aspects - the formation of extrapulmonary embolic material (embolus); mechanical obstruction of the pulmonary artery or its branches and the direct pulmonary hemodynamic disorders caused by it; and changes in pulmonary hemodynamics and respiration caused by the body fluid-reflex mechanism after embolism. The specific clinical etiology is as follows:

　　First, thrombosis leading to pulmonary embolism

　　An important foundation of modern diagnostic and therapeutic science is the recognition of the close relationship between deep vein thrombosis and pulmonary embolism. The vast majority of pulmonary embolisms can be considered as complications or clinical manifestations of deep vein thrombosis. Many foreign sources indicate that more than 90% of pulmonary embolisms with clinical manifestations have emboli originating from the proximal deep veins of the lower limb (popliteal vein, femoral vein). After the thrombus is dislodged, it travels through the circulation to the pulmonary artery and causes an embolism. Data also show that the incidence of pulmonary embolism concurrent with proximal deep vein thrombosis in the lower limb can reach more than 50%, but most have no obvious clinical symptoms. Venous thrombi originating from the gastrocnemius or beyond generally also do not have obvious clinical symptoms. This may be due to the fact that smaller thrombi do not cause significant changes in pulmonary hemodynamics. The risk of pulmonary embolism is highest in the early stages of deep vein thrombosis due to the friability of the thrombus and the relatively active fibrinolysis process. Stagnation of blood flow, hypercoagulability, hyper-viscosity, and venous endothelial injury are promoting factors for thrombosis. Therefore, factors such as trauma, surgery, long-term bed rest, varicose veins, diabetes, and obesity may all be risk factors for pulmonary embolism. Residual blood clots at the site of detachment of the proximal deep vein thrombus in the lower limb can also lead to recurrent pulmonary embolism.

　　Second, heart disease

　　It is considered to be the most common cause of pulmonary embolism in China, accounting for 40%. It can be seen in various types of heart disease, and it is more common in cases with atrial fibrillation, heart failure, and subacute bacterial endocarditis. The embolic material is mostly a thrombus in the right heart chamber, but it can also be a bacterial embolus.

　　Third, malignant tumors

　　It is believed to be a common cause of pulmonary embolism in China, accounting for 35%, and is common in lung cancer, digestive system tumors,绒癌, leukemia, etc. One-third of the emboli are tumor thrombi, and two-thirds are thrombi.

　　Elderly pulmonary embolism is prone to complications such as hemorrhage, right heart failure or shock, and even sudden death. Specifically as follows:

　　1. Hemorrhage

　　Due to abnormal coagulation function, degeneration of capillary endothelial cells, increased permeability, it is easy to cause exudative hemorrhage.

　　2. Right heart failure or shock

　　In the early stage, the blood flow to the heart and brain can maintain normal, and the general symptoms are not obvious. As the condition progresses, most patients begin to have symptoms such as pale skin, cold limbs, increased heart and respiratory rate, and decreased urine output. At this time, timely treatment is needed.

　　3. Sudden death

　　Mainly sudden cardiac arrest and respiratory arrest.

　　The clinical manifestations of pulmonary embolism are non-specific. They can be asymptomatic or slightly uncomfortable, or in severe cases, acute right heart failure or shock, even sudden death. The severity of the disease depends on the size of the embolus, the extent of blood flow obstruction, the location, and the speed of occurrence, as well as the patient's original cardiovascular and pulmonary function status. Some scholars summarize the clinical manifestations of pulmonary embolism into 4 types:

　　1. Pulmonary embolism type

　　Dyspnea (especially exertional dyspnea of unknown cause) and chest pain, in a few cases, there is also a small amount of hemoptysis. Chest pain can radiate to the shoulder or abdomen. The main signs include increased respiration and heart rate, pulmonary moist rales or wheezing. When accompanied by fibrinous pleurisy, pleural friction sounds can also be heard.

　　2. Pulmonary infarction type

　　Sudden dyspnea and chest pain, sometimes manifested as chest pain behind the sternum similar to myocardial infarction, and even syncope or shock. In addition to the above-mentioned signs, there may also be skin wetness, pallor, or cyanosis, and blood pressure drop.

　　3. Acute pulmonary heart disease type

　　Sudden severe dyspnea, chest pain, the feeling of near death due to asphyxia, restlessness, disturbance of consciousness, shock, syncope, and even sudden death. In addition to the above-mentioned signs, there may also be P2 augmentation, tricuspid regurgitant murmur, jugular venous distension, and positive hepatic jugular venous reflux, etc.

　　4. Chronic occlusive pulmonary arterial hypertension type

　　In addition to the manifestations of pulmonary hypertension, there is often a small amount of hemoptysis.

　　About 40% of patients have low or moderate fever, and a few patients have high fever in the early stage. The examination of both lower limbs often shows one-sided or bilateral swelling, which is often asymmetrical, accompanied by tenderness, superficial varicose veins, and other symptoms. 20% to 30% of patients with pulmonary embolism die due to delayed diagnosis and inadequate treatment. Timely diagnosis and anticoagulation, thrombolytic therapy can reduce the mortality rate to 8%. Therefore, early diagnosis is very important. Currently, the misdiagnosis rate and missed diagnosis rate of pulmonary embolism are very high. The main reason is that the awareness of diagnosis is not strong, and it is mistakenly believed that pulmonary embolism is rare in China. The atypical clinical manifestations of the disease are not well understood. Often, only when symptoms such as 'sudden severe chest pain, hemoptysis, dyspnea, cyanosis, and shadow on chest X-ray' occur, do people consider this disease. In fact, less than 1/3 of patients have so-called 'typical' symptoms, and most patients only have symptoms such as 'shortness of breath', especially in elderly patients.

　　Given that the vast majority of pulmonary emboli come from deep vein thrombosis in the lower extremities or right atrium, preventing vascular endothelial damage, correcting hypercoagulability and hyper-viscosity of blood, and preventing hemodynamic disorders (such as blood stasis and atrial fibrillation, etc.) are the key to preventing pulmonary embolism. Specific preventive measures include:

　　1. Avoid injecting drugs that irritate the venous wall, early removal of venous catheters, and active treatment of varicose veins;

　　2. Long-term bedridden individuals should avoid placing pillows under the popliteal fossa, encourage active lower limb movements and coughing on the bed, wear long-stocking elastic stockings or use intermittent compression of the lower limbs with an inflatable long-boot, and encourage early ambulation;

　　3. Actively treat hypercoagulability and hyper-viscosity of blood;

　　4. Actively treat deep vein thrombosis in the lower extremities, including thrombolysis, anticoagulation, and even surgical treatment;

　　5. Patients with peripheral thrombosis should especially maintain smooth defecation;

　　6. Correct atrial fibrillation, etc.

　　The clinical diagnostic tests for elderly pulmonary embolism are as follows:

　　1. Blood gas analysis

　　Decreased blood oxygen partial pressure, increased arterial carbon dioxide partial pressure.

　　2. White blood cell count

　　Normal or elevated, with accelerated erythrocyte sedimentation rate, elevated serum lactate dehydrogenase and creatine kinase.

　　3. X-ray chest film

　　The pulmonary texture in the blockage area decreases, local transparency increases, and there may also be patchy infiltration shadows, atelectasis, diaphragmatic elevation, pleural effusion, hump-shaped dense shadows convex to the hilum based on the pleura. Acute pulmonary heart disease type may also show enlargement of the right heart; chronic obstructive pulmonary arterial hypertension type may show widening of the right lower pulmonary artery and stunted root sign.

　　4. Electrocardiogram

　　Mild cases show no abnormalities, while severe cases may present with SⅠQⅢTⅢ signs similar to acute pulmonary heart disease, pulmonary P waves, right bundle branch block, and so on.

　　5. Pulmonary arteriography

　　It is the 'gold standard' for diagnosing pulmonary embolism, which can accurately understand the location and extent of the embolism, but it has certain risks for the elderly. It is only used when other means are difficult to make a clear diagnosis, and the benefits and risks are weighed before adoption.

　　6. Pulmonary radionuclide scan

　　Pulmonary perfusion scanning with radioactive labeled human serum albumin, where the embolism area has rare or absent radioactivity, but it must exclude other pulmonary lesions. The combination of radionuclide perfusion lung scanning with radionuclide aerosol lung ventilation scanning can significantly improve the positive rate and accuracy of diagnosis.

　　7. D-dimer detection

　　D-dimer is a good marker for the degradation of fibrin in the body, with high sensitivity for pulmonary embolism (95% to 98%), but poor specificity (30% to 40%). The negative detection of D-dimer has great value in excluding pulmonary embolism as a diagnosis.

　　8. Spiral CT and MRI

　　It also has certain value in the diagnosis of pulmonary embolism.

　　9. Venography of the lower extremities

　　It is the 'gold standard' for diagnosing deep vein thrombosis in the lower extremities, but it may cause embolus detachment and is now less commonly used.

　　10. Doppler vascular examination of the lower extremities

　　Nuclear venography, volume impedance imaging, real-time (B-type) ultrasound examination, and all are commonly used methods for diagnosing deep vein thrombosis in the lower extremities, which have high sensitivity and specificity.

　　For elderly patients with pulmonary embolism, dietary adjustment should follow the basic principle of preventing dryness and protecting yin, nourishing the lungs and moistening the lungs. Eating more sesame, walnuts, fresh lotus root, pears, honey, silver ear, mung beans, etc., can play a role in nourishing the lungs, moistening the lungs, and nourishing the blood. The diet should be light and refreshing. Spicy and dry products such as scallion, ginger, cinnamon, star anise, and chili should not be eaten in large quantities. Hot foods such as fatty meat, animal oil, lamb, dog meat, smoked and fried foods should be avoided. Complementary foods can be taken when necessary, but they should be clear and nourishing.

　　There are many foods that can nourish the lungs in life, such as radish can treat symptoms such as lung heat cough and thick phlegm, water chestnuts are effective for symptoms such as injury to fluid, phlegm heat, and cough, while pears have the effects of clearing phlegm, soothing the lungs, detoxifying and diuretic, silver ear can treat symptoms such as yin deficiency lung dryness, dry cough, and thick phlegm, and lily can alleviate symptoms such as cough, insomnia, and neurasthenia.

　　Each person can choose according to their own specific situation. It is necessary to understand clearly the efficacy of food, such as eating water chestnuts can clear heat and generate fluid, both raw and boiled water can be consumed. Eating radish is more suitable for those with abundant phlegm and cough. Eating lily, boiling it into porridge or drinking it in water is more effective. Mung beans are suitable for people with strong internal fire. Due to the great differences in individual quality, food should be selected according to personal conditions, and at the same time, it is necessary to avoid eating too spicy, salty, greasy and other foods.

　　After the diagnosis of pulmonary embolism, active treatment should be started immediately. The treatment measures for pulmonary embolism mainly include: general management, symptomatic treatment, thrombolytic therapy, anticoagulation therapy, and surgical treatment. The specific details are as follows:

　　General Management

　　Bed rest, oxygen inhalation, and high-frequency jet or oscillating oxygenation may be given when necessary. Maintaining smooth defecation and avoiding the large-scale detachment of peripheral emboli are all very important measures.

　　Symptomatic Treatment

　　Maintain a stable hemodynamic status, correct shock and heart failure in a timely manner, administer low molecular weight dextran for fluid expansion and improvement of blood rheology, and give analgesics to severe chest pain patients. Cyproheptadine and ketanserin can effectively relieve the spasm of blood vessels and airways caused by embolism.

　　Thrombolytic Therapy

　　There is still controversy about thrombolytic therapy for pulmonary embolism or deep vein thrombosis. However, for pulmonary embolism with large clots (above two lung lobes) or with hypotension occurring within 5 days, thrombolytic therapy is still recommended for most patients without contraindications. In China, urokinase is commonly used, with the usual method being an initial dose of 2000 to 4400U/kg intravenously within 10 to 30 minutes, followed by a continuous intravenous infusion of 2000 to 4000U/kg per hour for 12 to 24 hours, followed by anticoagulation therapy. Another commonly used drug is alteplase (recombinant tissue plasminogen activator, rt-PA), which selectively dissolves fibrin in formed thrombi and theoretically only has local thrombolytic effects without systemic thrombolytic effects, making it safer. The dose is 40 to 100mg intravenously for more than 2 hours, with the addition of heparin.

　　IV. Anticoagulation Therapy

　　Although it cannot directly dissolve thrombi, it can prevent the further occurrence and development of thrombi. For some patients with mild conditions, anticoagulation therapy alone can also achieve satisfactory efficacy through the body's own fibrinolysis process. Commonly used drugs are heparin (heparine) and warfarin (warfarin). Heparin is generally used during the initial stage of anticoagulation and after thrombolysis, which can prevent thrombus formation and blood clot spread. The dose is 15,000 to 30,000 U/d, controlling the coagulation time to 1.5 to 2 times of normal, and administered intravenously or subcutaneously in divided doses, with adjustments made according to the coagulation monitoring results. Generally, heparin is used for 7 to 10 days before warfarin is added, and it is changed to oral warfarin alone after 3 to 5 days. Studies have shown that low-molecular-weight heparin has the same efficacy as conventional heparin preparations but has fewer hemorrhagic complications. Warfarin is often used for maintenance therapy, with an initial dose of 10 to 15 mg, halved the next day, and then maintained at 2.5 to 7.5 mg daily, with the specific maintenance dose adjusted according to the coagulation status. In the past, it was required to control the prothrombin time to 1.5 to 2.5 times the control value, and the bleeding complications were more. Recently, overseas recommendations for warfarin maintenance therapy are to control the prothrombin time to 1.3 to 1.6 times the control value. The duration of warfarin therapy is generally 3 to 6 months. Natural and leeches (recombinant leeches) can prevent thrombus formation and have a good application prospect in the prevention and treatment of thrombosis and pulmonary embolism, and are currently under further research.

　　V. Surgical Treatment

　　There are two types of surgical methods.

　　1. Pulmonary thrombectomy: It has a high mortality rate and is only suitable for those who cannot correct shock after active treatment such as thrombolysis and vasopressin. For those with pulmonary artery thromboembolism that has not been dissolved and has become organized and invaded the vascular wall, causing chronic pulmonary hypertension, thrombectomy of the thrombus and intimal resection should be performed, as reported, the mortality rate is less than 13%.

　　2. Infrarenal vena cava occlusion: To prevent the recurrence of pulmonary embolism caused by the detachment of lower limb or pelvic venous thrombi, vena cava pleating, ligation, or vena cava filter implantation can be considered.