Neonatal Wilson-Mikity syndrome

　　1. Etiology

　　The etiology has not been fully elucidated. Due to the underdevelopment of the lungs, the respiratory units vary, and the alveoli of the respiratory bronchioles require increased ventilation pressure and resistance due to variations in quantity and morphology. It mainly occurs in premature infants.

　　2. Pathogenesis

　　Due to abnormal distribution of pulmonary gas, the ratio of ventilation to perfusion is disordered, lung compliance decreases, airway resistance increases, CO2 retention occurs, PaO2 decreases, and cyanosis and dyspnea appear. The more immature alveoli, the more severe the symptoms.

　　Early pathological changes are indistinguishable from immature lungs, with linear alveolar epithelium. In the late stage, alveoli expand, with atelectasis around them. The muscular layer of pulmonary vessels thickens, with a pulmonary artery radius of 100U, a middle layer thickness of 20U, which is 1.3 times thicker than the fetal pulmonary vessel muscular layer. BPD is 11-16U (fetal 14.7U, neonatal 9U, 6 months 7.8U, 1 year 7U). The pathogenesis of pulmonary vessel hypertrophy is related to chronic hypoxia.

　　Complications include respiratory distress, hypoxemia, hyperphosphatemia, pulmonary heart disease, heart failure, pulmonary hypertension, recurrent respiratory tract infections, emphysema, wheezing, etc. Some cases present pulmonary heart disease, heart failure, pulmonary hypertension, incomplete gas exchange, and must be ventilated artificially. Due to repeated respiratory tract infections, oxygen dependence, the prognosis is poor. Mild heart failure, respiratory tract infection, wheezing, dyspnea, and cyanosis improve 1-2 weeks, tracheal retraction disappears around 1 year old, with residual chronic emphysema.

　　The onset is often within the first week after birth or later, with a slow onset, manifested as intermittent cyanosis, increased respiratory rate, tracheal retraction signs, and the respiratory symptoms gradually worsen from 2 to 6 weeks after onset, manifested as dependence on oxygen and severe respiratory distress, which can last for several months. According to the condition, Fujimura Masashi divided this syndrome into 4 types.

　　Type Ⅰ (respiratory insufficiency, pulmonary heart type) has dyspnea for more than 12 months, with hypoxemia, hypercapnia, among which some cases present pulmonary heart disease, heart failure, pulmonary hypertension, incomplete gas exchange, and must be ventilated artificially. Due to repeated respiratory tract infections, oxygen dependence, the prognosis is poor.

　　Type Ⅱ (effortful breathing type) has moderate tracheal retraction breathing, hypoxemia, hypercapnia, but can have mild heart failure, respiratory tract infection, wheezing, dyspnea, and cyanosis improving 1-2 weeks, tracheal retraction disappearing around 1 year old, with residual chronic emphysema.

　　Type Ⅲ (tracheal retraction respiratory type) has a milder tracheal retraction sign than Type Ⅱ, with increased respiratory rate, blood gas analysis within the normal range, no need for oxygen, and transient wheezing.

　　Type Ⅳ (transient wheezing type) is the mildest type, with increased respiratory rate, mild tracheal retraction, and an average disappearance of 2-3 months, with transient wheezing in the neonatal period.

　　The etiology has not been elucidated, but it is related to factors such as intrauterine infection, repeated aspiration of milk, oxygen toxicity, or hypoxia. Therefore, it is necessary to do a good job of prenatal health care, prevent various infectious diseases, do a good job of perinatal health care, prevent intrauterine and postnatal hypoxia, prevent oxygen toxicity during oxygen therapy for various hypoxic diseases, and other issues that should be noted for the prevention of this syndrome. Pregnant women should not drink too much or too strong tea, because the theophylline (caffeine) in tea has an excitatory effect, which can increase fetal movement and even harm fetal growth and development.

　　1. Chest X-ray examination

　　The X-ray features are widespread honeycomb-like air cysts in both lungs, thick walls, overinflation of both lungs, diffuse air cysts in both lungs of type I and II, infiltration around both hilum, streak shadows extending to both upper and lower lung fields, confluent emphysema, and the formation of mediastinal hernia. Chest X-ray of type III and IV shows small round air cysts. All have osteoporosis accompanied by multiple fractures of the posterior ribs.

　　2. Pulmonary function testing

　　Indicates a decrease in functional residual capacity and tidal volume, and an increase in airway resistance.

　　In terms of nursing care, close observation should be made, early detection should be made, and attention should be paid to differentiate from respiratory distress syndrome and aspiration pneumonia. Appropriate oxygen should be supplied during the stages of tachypnea and cyanosis, and intermittent oxygen therapy can be used. If cyanosis is not obvious, oxygen supply can be paused. Those who cannot suckle should not be forced to do so to avoid vomiting and aspiration. For those who are restless, certain sedatives or diuretics can be given to prevent cerebral edema caused by hypoxia.

　　Children with cyanosis can be given 40% oxygen to maintain PaO2 at 6.67～10.7kPa (50～80mmHg), and those with marked respiratory distress and difficulty in breastfeeding can be fed through a gastric tube. Since there is already a lot of fluid in the lungs, the intake of fluids should be appropriately controlled. In case of acid-base imbalance, intravenous fluid replacement should be given. Cases with a course of disease exceeding 2 days can be treated with antibiotics to prevent secondary infection. Dexamethasone can be administered intravenously to reduce pulmonary edema in cases of restlessness.

　　1. Treatment

　　It is mainly symptomatic treatment, oxygen supply during hypoxia to maintain PaO2 at 8.0～10.7kPa (60～80mmHg), but try to avoid mechanical ventilation. Maintain water and electrolyte balance and appropriate calorie intake; use antibiotics during infection; digoxin, diuretics, and vasodilator drugs can be used in heart failure; pulmonary surfactant is given to improve lung compliance and prevent the occurrence of pulmonary hyaline membrane disease.

　　2. Prognosis

　　The late stage of the first period is a critical period, 23% of children die of respiratory failure during this period, and the overall mortality rate is 25% to 50%. Complete cure requires several months to 2 years, and 1/4 to 1/3 of the surviving cases have central nervous system disorders, which may include seizures and intellectual impairment.