Pediatric pulmonary embolism

　　First, Etiology

　　The source of emboli in pediatric pulmonary embolism is different from that in adults. Since pediatric lower limb DVT and pelvic thrombosis are less common, PE caused by embolism detachment from these areas is not a common cause. The source of emboli in children is more scattered, and it is more common to be caused by congenital diseases (such as congenital heart disease, sickle cell anemia, etc.) or iatrogenic factors (such as indwelling venous catheters, parenteral nutrition) compared to adults. 90% of pulmonary embolism originates from thrombosis in the lower limb veins (femoral veins and pelvic veins). Certain diseases such as bacterial endocarditis, myocarditis, nephrotic syndrome after hormone treatment, leukemia, polycythemia, thrombocytopenia, or complications after otolaryngological, urinary, and intestinal infections, as well as complications after intravenous infusion, cardiac catheterization, and surgery. It can also be seen in children who have been lying in bed for a long time, malnutrition, diarrhea with dehydration, and occasionally in sickle cell anemia. Fat embolism is more common after fractures.

　　Second, Pathogenesis

　　The formation of venous thrombosis is related to the following 3 causes:

　　1. Venous blood stasis.

　　2. The endothelial or epithelial cells of blood vessels are damaged.

　　3. The coagulability of blood increases.

　　After thrombosis, for some reason, the clot may break off, flow into the right ventricle of the heart along the venous system, enter the pulmonary artery, and become embedded in a pulmonary artery of varying sizes from the blockage. Due to the obstruction of blood flow, local lung tissue may develop atelectasis and the loss of surfactant substances.

　　Pulmonary embolism itself is often a complication of bacterial endocarditis, myocarditis, nephrotic syndrome after hormone treatment, leukemia, polycythemia, thrombocytopenia, or complications after otolaryngological, urinary, or intestinal infections. In addition, complications may occur after intravenous infusion, intracardiac catheter examination, surgical operation, long-term bed rest, malnutrition, diarrhea and dehydration, etc. Severe or extensive pulmonary embolism cases, acute respiratory failure and heart failure are common complications of pulmonary embolism.

　　The clinical manifestations of pediatric PE are similar to those of adults, with symptoms and signs lacking specificity and varying greatly, ranging from asymptomatic to hemodynamic instability, even sudden death.

　　1. Symptoms of pulmonary embolism

　　Symptoms include dyspnea and tachypnea, especially after activity, chest pain, including pleuritic chest pain or angina-like chest pain; syncope can be the only or initial symptom of pulmonary embolism, restlessness, anxiety, or a sense of impending death; usually small amounts of hemoptysis, massive hemoptysis is rare, cough, palpitations; massive or extensive pulmonary embolism can cause acute pulmonary heart disease.

　　2. Signs

　　Symptoms include shortness of breath, tachycardia, blood pressure changes, and in severe cases, blood pressure can drop even into shock. Cyanosis, fever, mostly low fever, a few patients may have moderate or higher fever; jugular venous distension or pulsation, lung auscultation may hear wheezing and/or moist rales, occasionally vascular杂音 can be heard, pulmonary valve second sound hyperemia or splitting, P2>A2, tricuspid valve area systolic murmur; there may be signs of pleural effusion.

　　Prevention of pulmonary embolism and infarction mainly involves long-term patients, especially those who have undergone surgery, who should pay attention to early active and passive activities, massage therapy, to reduce the opportunity for blood stasis. Attention should be paid to fluid intake, avoiding blood circulation stasis or congestion. Maintaining nutrition is also important. Prevention of PE can use venous filters, suitable for patients with lower limb venous thrombosis, to prevent emboli from falling into the lung.

　　I. Examination

　　1. Non-specific examination:

　　Including blood routine.

　　2. Arterial blood gas analysis:

　　Blood gas often shows hypoxemia and低碳酸血症, with an increased partial pressure difference of oxygen between alveolar and arterial blood (PA-αO2), which can be normal in some patients.

　　3. Plasma D-dimer (D-dimer)

　　This examination has become an important preliminary screening test for clinical diagnosis of pulmonary embolism (PE). D-dimer is a soluble degradation product of cross-linked fibrin produced under the action of the fibrinolytic system, serving as a specific marker for the fibrinolytic process. During thromboembolism, due to the dissolution of thrombus fibrin, its concentration in the blood increases. The diagnostic sensitivity of D-dimer for acute PE reaches 92% to 100%, but its specificity is low, only 40% to 43%. Surgery, tumor, inflammation, infection, tissue necrosis, and other factors can all cause it to increase. If its content is below 500 μg/L, acute PE can be basically ruled out. Electrocardiogram, pulmonary function, echocardiogram, and other tests have certain indicative significance, but cannot be used as a basis for diagnosis.

　　II. Auxiliary Examinations

　　1. Pulmonary X-ray examination:

　　There are often abnormal findings, such as: regional thinning, sparseness, or disappearance of pulmonary vascular markings; local infiltrative shadows in the lung field, wedge-shaped shadows with the tip pointing to the hilum; atelectasis or incomplete lung expansion, etc.

　　2. Electrocardiogram:

　　About 30% show abnormalities, commonly V1 to V4 T-wave changes and ST-segment abnormalities, right bundle branch block, electrical axis deviation to the right, counterclockwise rotation, etc., but these changes are non-specific. Early changes in X-rays and electrocardiograms are often not obvious, and it is easy to miss the diagnosis.

　　3. Radionuclide lung ventilation/perfusion scan:

　　It is an important diagnostic method for PE. Typical signs can serve as the basis for diagnosis. The distribution of radionuclides is proportional to pulmonary blood flow, showing sparse or defective distribution in pulmonary lobes, segments, or multiple sub-segmental pulmonary areas, while ventilation imaging is normal or nearly normal.

　　4. Spiral CT and Electron Beam CT Angiography:

　　Due to its non-invasive nature, it has attracted attention and can detect emboli in pulmonary arteries above the segment level, making it one of the diagnostic examinations.

　　5. Magnetic Resonance Imaging (MRI)

　　It has high sensitivity and specificity for diagnosing pulmonary artery thrombi at the segment level or above, and is more acceptable to patients. MRI has the potential to identify old and new thrombi, and may become the basis for determining thrombolytic therapy in the future.

　　6. Pulmonary angiography:

　　It is still the 'gold standard' for diagnosing PE, with a sensitivity of 98% and specificity of 95% to 98%, but due to its invasiveness, it is not used as a first-line examination method.

　　1. Consume light, easy-to-digest, vitamin-rich, high-fiber, and low-fat diets, eat less raw, hard, and foods containing chicken bones, fish bones, etc., to prevent damage to the digestive tract mucosa and cause gastrointestinal bleeding; ensure adequate nutrition during the recovery period of the disease, such as milk, eggs, lean meat, and avoid eating foods rich in vitamin K, and eat more beneficial foods.

　　2. Foods such as spinach, kale, liver, etc., especially during warfarin treatment, due to increased vitamin K intake, can reduce the effect of warfarin, which is to inhibit the synthesis of K-dependent coagulation factors.

　　3. Dietary attention should be low in sodium, avoid smoking and drinking, and do not overeat spicy, fried, or preserved items; eating spicy and greasy foods can severely stimulate the mucous membranes of the heart and lungs, causing them to become highly congested and move faster, leading to severe abdominal pain and diarrhea, and causing the thrombus to rapidly detach and form new obstructions, triggering pulmonary embolism. Therefore, those suffering from esophagitis, pulmonary embolism, cerebral thrombosis, gastric ulcer, and hemorrhoids, among other diseases, should eat less or avoid chili peppers. Since chili peppers are characterized by their strong pungency and heat, conditions such as fire eyes, sore throat, hemoptysis, boils, and carbuncles, or hypertension with yin deficiency and fire excess, cervical spondylosis, and femoral head disease should also be eaten cautiously.

　　I. Treatment

　　1. Internal Medicine Treatment

　　(1) General management: For children highly suspected or diagnosed with PE, close monitoring should be carried out, and children with massive PE can be admitted to the ICU; to prevent emboli from falling off again, it is required to stay in bed absolutely, keep the bowels smooth, avoid exertion; for children with obvious restlessness, appropriate sedation should be given; for those with chest pain, analgesics can be given; for symptoms such as fever and cough, appropriate symptomatic treatment should be given.

　　(2) Respiratory and circulatory support therapy: 10% of acute PE cases die within 1 hour of the onset of the disease, so it is very necessary to quickly stabilize hemodynamics, maintain appropriate oxygen therapy and ventilation before anticoagulation and thrombolytic therapy, and any child suspected of PE may have the possibility of implementing cardiopulmonary resuscitation measures. However, tracheotomy should be avoided to prevent excessive bleeding locally during anticoagulation or thrombolytic therapy.

　　(3) Thrombolytic therapy: Thrombolytic therapy is suitable for fresh thrombosis or pulmonary thromboembolism within 5 days, suitable for patients with massive PE, shock, and hypotension. Common thrombolytic drugs include urokinase (UK), streptokinase (SK), and recombinant tissue plasminogen activator (rtPA).

　　(4) Anticoagulant therapy: Anticoagulant therapy is the basic treatment for PE and DVT, which can effectively prevent the recurrence of thrombosis and the formation of new thrombosis, while the body's own fibrinolysis mechanism dissolves the thrombosis that has formed. At present, the anticoagulant drugs mainly used in clinical practice are heparin, which has high safety and does not require laboratory routine monitoring of coagulation function during clinical medication.

　　2. Surgical treatment

　　(1) Surgical thrombectomy: Suitable for the following three types of patients:

　　① Acute massive pulmonary embolism patients.

　　② Contraindications to thrombolytic therapy.

　　③ Ineffectiveness of thrombolytic therapy and other active medical treatments.

　　(2) Applicability of venous filters: Used for the prevention of pulmonary embolism (PE), suitable for patients with lower limb venous thrombosis, to prevent emboli from falling into the lung. There is little experience with children, and the long-term follow-up of Cahn et al. on children with inferior vena cava filters showed that their effectiveness and safety in preventing PE are good and similar to those of adults.

　　II. Prognosis

　　Once the diagnosis of the child is clear, active and regular treatment should be given to prevent recurrence. In cases of massive or extensive pulmonary embolism, surgical embolism excision surgery is adopted, but the mortality rate of surgery is still high. In addition, acute respiratory failure and heart failure, etc., are also common causes of death in children, and should not be ignored.