The functions of the drainage tube mainly include draining the fluid out of the body, assessing the severity of the disease, and injecting medication for cleaning, etc. The details are as follows: First, draining the fluid out of the body: if there is a significant localized accumulation of fluid, the drainage tube is capable of draining the fluid out of the body, in order to prevent it from becoming infected or causing the patient to experience significant pain. Second, to assess the severity of the disease: through the drainage tube drainage, can observe the amount of drainage, then can assess the severity of the disease. At the same time, the drainage fluid can also be used to consider whether the patient is bleeding or infected and other factors, to provide an assessment basis for the continuation of treatment. Third, injection of drugs for cleaning: if there is obvious local infection, you can inject the appropriate drugs into the drainage tube to clean the local area, so that the infection can be further controlled. The drain needs to be protected to prevent it from coming out of the body, and the local area should be changed regularly to prevent infection. For other precautions, consult the attending physician.