Management of pulmonary hypertension crisis after cardiac surgery: The pulmonary circulation is a low pressure and low resistance system. The normal pulmonary artery pressure is 22/12mmHg, with a mean pressure of 17mmHg. The resistance of the pulmonary arteries is low, which facilitates gas exchange and is less likely to produce pulmonary edema, while the pulmonary vessels have a high degree of diastolic capacity, and blood flow increases 2-3 times without increasing pressure. Pulmonary hypertension is defined as pulmonary artery pressure exceeding the highest normal value, i.e., bilateral pulmonary artery pressure greater than 30/5mmHg and mean pressure greater than 22mmHg. It is divided into hyperdynamic, obstructive and occlusive types. In congenital heart disease such as ventricular septal defect, atrial septal defect and arteriovenous ductus arteriosus, chronic elevation of pulmonary artery pressure is often combined with progressive histological changes in the middle layer and intima of pulmonary arteries and small arteries, resulting in progressive development of pulmonary hypertension from hyperdynamic type to obstructive type and continuous increase of pulmonary artery pressure. When the right heart pressure is greater than the left heart pressure, a right-to-left shunt occurs, i.e., Eisenmenger syndrome, and the opportunity for surgery is lost at this time. In general, as the pulmonary artery pressure increases, the greater the likelihood of postoperative pulmonary hypertension crisis and the greater the surgical risk. However, it is sometimes difficult to accurately determine the indication for surgery. Pulmonary hypertension crisis is a clinical crisis state in which pulmonary vasoconstriction occurs on the basis of pulmonary hypertension, which increases the resistance of pulmonary circulation and obstructs right heart blood expulsion, resulting in sudden pulmonary hypertension and low cardiac output. Treatment of pulmonary hypertension crisis: The hemodynamic changes that occur in pulmonary hypertension crisis are mainly due to the sudden increase in pressure in the right heart system causing low cardiac output in the left heart. The method of administration can be given through the central vein, or through the left and right atria, respectively, and nitric oxide (NO) inhalation is also used to reduce pulmonary hypertension, depending on the specific situation. Inhalation of high concentration of oxygen and correction of acidosis are not further discussed. Prevention of pulmonary hypertension: preoperative oxygen, oral captopril, intravenous PGE1 and other treatments can reduce pulmonary artery pressure. During the operation, anesthesia should be smooth, and drugs that stimulate the lung should be used as much as possible. After surgery, we should further improve cardiac function, pay attention to sedation, reduce adverse stimulation, apply positive inotropic drugs, and continue to apply PGE1 to reduce postoperative reactive pulmonary hypertension and prevent pulmonary hypertension crisis.