Pulmonary effusion is clinically called pleural effusion, which is a condition of abnormal increase of fluid in the pleural cavity. When the fluid increases to a certain degree, it will cause some compression on the lung tissue, so aspiration is needed to decompress and release the compression on the lung tissue, thus relieving the clinical symptoms. Therefore, pleural effusion aspiration is thoracentesis drainage is a routine minimally invasive operation in clinical practice, and the operation is relatively smooth and without complications for most patients, so it is not dangerous for most patients. However, there are some patients who may have some unpredictable risks during the operation. The more common ones are hemothorax, pneumothorax, and in more serious cases, pleural allergic reactions like dizziness, pallor, sweating, palpitations, chest pressure or pain, fainting, etc. More serious cases even appear like pulmonary edema, anaphylaxis, etc., but these are relatively rare.