High-altitude pulmonary edema

　　During the course of the disease, attention should be paid to whether there is concurrent pulmonary infection, and observe for signs of shock, heart failure, early coma, and pulmonary embolism as complications.

　　The diagnosis of pulmonary edema is mainly based on symptoms, signs, and X-ray findings.

　　Early diagnostic methods: measurement of pulmonary artery wedge pressure and plasma colloid osmotic pressure, if the pressure difference is less than 4 mmHg, pulmonary edema is inevitable.

　　Continuous measurement of chest base impedance (thoracic fluid index, TFl) reveals an increase in pulmonary water when TFl decreases.

　　1. Symptoms

　　The disease usually manifests within 24 to 72 hours after arrival at high altitude, often accompanied by extreme fatigue, severe headache, chest tightness, palpitations, nausea and vomiting, difficulty breathing, and frequent dry cough, symptoms worsen at night, making it difficult to fall asleep, cyanosis of the lips and nail beds, an increased heart rate, rapid and shallow breathing, the respiratory rate can reach 40 breaths/min, some patients may experience chills and low fever, pale complexion, wet and cold skin, as the condition progresses, breathing difficulties intensify, a few patients may not be able to lie flat and have to breathe in a sitting position, coughing up frothy sputum, initially white or pale yellow, later turning pink, in large quantities, it can涌出 from the mouth and nose, neurological symptoms include confusion, hallucinations, sensory dullness, and in severe cases, coma.

　　2. Signs

　　The most important sign is the presence of crepitations and moist rales in the lungs, in severe cases, the sound of air passing can be heard by simply placing the ear against the chest wall, rales are most commonly found at the base of both lungs, but they can also appear unilaterally, the second sound of the pulmonary artery area is hyperactive, some patients may hear grade II to III systolic murmurs in the precordial area, in cases of right heart failure, the jugular veins become distended, there is edema, the liver is enlarged with tenderness, Hultgren's statistics of 150 patients show that 26.7% have a heart rate >120 beats/min, 26% have a respiratory rate >24 breaths/min, 11% have a blood pressure >150/90 mmHg, 20% have a body temperature of 38℃, fundus examination shows retinal varices, arterial spasm, disc congestion, scattered punctate or flame-shaped hemorrhagic spots.

　　1. Learn more about the characteristics of the plateau climate before entering the plateau, understand the knowledge of high-altitude diseases, and eliminate the fear of the plateau environment.

　　2. A strict health check-up must be conducted before entering the plateau.

　　3. Pay attention to keeping warm and preventing colds.

　　4. In the first week after arriving at high altitude, attention should be paid to rest, gradually increase the amount of activity, avoid and minimize strenuous exercise, and avoid overexertion.

　　5. People who have had high-altitude pulmonary edema are prone to recurrence.

　　6. Drug prevention: Yan Nao, Hong Jing Tian capsules.

　　1. Acute high-altitude disease and normal blood gas analysis at an altitude of 4558m.

　　1. The pulmonary X-ray manifestations are earlier than the clinical signs, with significant diagnostic value. The pulmonary field transmittance is weakened, and there are scattered patchy or fluffy blurred shadows, which are more pronounced near the hilum and can form butterfly-shaped shadows; the lesions can be localized or asymmetrical in both pulmonary fields; in severe cases, the concentration of fluffy shadows is high, the range is wide, and they merge into cotton ball-like shapes.

　　2. Laboratory examination can include blood and urine routine tests, blood electrolytes and blood gas analysis, liver and kidney function, electrocardiogram, and other examinations, depending on the condition.

　　Diet should be light, with a high intake of vegetables and fruits, a reasonable diet, and attention to sufficient nutrition. Try to eat high-sugar foods, adjusting the structure to first carbohydrates, second fats, and third proteins. If possible, consume more liquid energy, such as fruit juice, meat soup, milk, and it can also supplement some water. Milktea is a very good food, and butter tea is also good, as it is a high-calorie food with a high fat content, which is protective and moisturizing for the skin. The theophylline inside can also have a diuretic effect.

　　First, treatment

　　Early diagnosis is the key to effective treatment. In developed countries, due to the modernization of high-altitude emergency facilities, once pulmonary edema occurs, it is quickly transferred to low-altitude areas. However, in the Qinghai-Tibet Plateau of China, it is advocated to save the patient on the spot to avoid death on the way due to long-distance transfer, road bumps, or oxygen supply interruption. Yang et al. treated 54 cases of various types of high-altitude pulmonary edema at an altitude of 4800-5200m with on-site treatment, with a cure rate of 100%.

　　1. Oxygen therapy:Inhaling high-concentration, high-flow oxygen is the key to saving the patient. 100% oxygen, infused at a rate of 4-8L/min. When the patient has a large amount of frothy sputum, a defoaming agent such as 50%-70% ethanol or dimethyl silicone oil can be used. If conditions permit, hyperbaric oxygen therapy can also be used. After oxygen administration, blood oxygen saturation should be increased rapidly, pulmonary artery pressure reduced, and symptoms improved, but oxygen administration should be continued for 12-24 hours until the patient is completely recovered.

　　2. Drug treatment

　　(1) Aminophylline: It is a very effective drug for treating high-altitude pulmonary edema, which can reduce pulmonary artery pressure, strengthen the heart, diuretic, and dilate the smooth muscle of the bronchial tubes. The initial dose is 5-6mg/kg diluted in 40ml of 25%-50% glucose and administered slowly by intravenous injection. According to the condition, it can be repeated every 4-6 hours.

　　(2) Diuretics: It can dehydrate, reduce blood volume, alleviate right ventricular workload, and reduce pulmonary vascular resistance. Furosemide (Lasix) is commonly used at 20mg diluted in 20ml of 25% glucose for intravenous injection, or etacrynic acid (sodium ethacrylate) 25-50mg for intravenous injection. When diuretics are used, it is important to supplement potassium chloride to prevent hypokalemia and hypochloremia, and also to pay attention to blood thickening.

　　(3) Vasodilators: Nifedipine (nifedipine) can block calcium influx into vascular smooth muscle, reduce vascular resistance, and improve microcirculation. The dosage is 50mg, twice daily. Phentolamine, an alpha-adrenergic antagonist, can dilate systemic small arteries and large veins and has a positive inotropic effect. The dosage is 5-10mg diluted in 20-40ml of 50% glucose and administered slowly intravenously. Isosorbide dinitrate (nitroglycerin) can directly act on vascular smooth muscle, dilate small arteries and veins, and excite the myocardium. The dosage is 10mg every 6 hours.

　　(4) Corticosteroids: In patients with high-altitude pulmonary edema, adrenal cortical function may be impaired, so the use of corticosteroids in some severe cases is effective. It can stabilize the function of vascular endothelial cells and alveolar epithelial cells, reduce capillary permeability, relieve bronchospasm, and promote the absorption of pulmonary exudate. Hydrocortisone is commonly used at 200-300mg intravenously, or dexamethasone 10-20mg intravenously.

　　(5) Morphine: Some have proposed that morphine can suppress the respiratory center, so it should be contraindicated. However, morphine can be very effective for some critically ill patients. Its action is to eliminate anxiety and unease, reduce central venous pressure, decrease pulmonary blood volume, and reduce ventricular workload. Therefore, morphine can be used for severe patients with restlessness, severe cough, copious frothy sputum, and laborious breathing. However, morphine should not be used for patients with drowsiness, coma, shock, or irregular breathing. The dosage is 5-15mg administered subcutaneously or intramuscularly.

　　(6) Others: If the patient develops heart failure, respiratory failure, or respiratory tract infection, strong heart, respiratory stimulation, and anti-infection treatments should be administered according to symptoms and condition.

　　II. Prognosis

　　Discover symptoms early and treat them promptly. Generally, the prognosis is good. Delayed diagnosis and treatment can be fatal.