Drainage usually refers to the clinical way to drain exudate, blood, pus, etc. from the chest, abdominal cavity and other parts of the body by means of negative pressure suction through skin gauze or drainage tubes, and it is generally considered that no new exudate is drained for a period of time. The purpose of using skin gauze drainage is mostly to drain infectious exudate such as pus from the wound site. After the surgical operation of incision and drainage of the abscess, the skin gauze is inserted at the incision to drain the pus. Usually, when the gauze is replaced without blood or with only a small amount of exudate, the wound granulation tissue is fresh and tends to heal, and basically the drainage is considered clean and the drainage gauze can be removed. Drainage tube drainage is a surgical procedure in which the drainage tube is placed on the site of high exudate or bleeding in the surgical wound and fixed to the body surface by making a hole on the body surface. Usually the drainage fluid is yellowish in 48-72 hours after surgery, and the drainage is considered clean when the flow is less than 20 mL, and the drainage tube can be removed. If the drainage fluid is viscous or causes negative pressure suction resulting in blockage of the tube, notify the physician of any abnormalities.