There is no strict danger period, but in general the first day after surgery, especially the night of surgery, is prone to sudden changes in condition. The heart is the “main engine” of the human body, so heart surgery is of course more risky than surgery on other organs. The overall post-operative recovery includes two major areas: 1, heart function: can be simply understood as the heart rate and blood pressure, in small to medium doses of cardiac drugs to maintain a stable heart rate, blood pressure, is a more ideal state. If the application of high doses of cardiac drugs, indirectly suggest poor cardiac function. 2, lung function: The lungs are the second heart of the human body, and after surgery, they generally need ventilator-assisted breathing, and when the heart function is stable and lung function is restored, then the ventilator can be removed. So, going to the ventilator is also a very important hurdle. Is the ventilator removed to pass the dangerous period? No, it is not. A normal person is ventilated by negative pressure, while a ventilator is ventilated by positive pressure, which turns out to be different. After the ventilator is removed, the child starts to breathe on his own, and the mode of ventilation changes, which requires adaptation, especially in cases of preoperative pneumonia, postoperative sputum, young age, complicated precordial surgery, combined pulmonary hypertension, etc. It is easy to fail to withdraw the ventilator, that is, to bring it back after removing it, and if you need to bring it again, the doctor will tell you.