The purpose of fasting and water fasting for 6 hours after anesthesia is to avoid nausea, vomiting, and obstruction of the airway in postoperative patients due to anesthesia. During the period of anesthesia, patients will have muscle relaxation, and it is difficult for them to control their ability to eat, and after 6 hours of fasting and water fasting, patients have finished metabolizing the anesthetic drugs, and the swallowing function is restored, which can prevent choking and coughing, and prevent food and water from entering into the respiratory tract, leading to asphyxia and inhalation pneumonia. After anesthesia, the patient’s gastrointestinal function is yet to be recovered, and eating at this time is easy to induce nausea and vomiting. Postoperative rehydration therapy can be carried out routinely. If the patient undergoes non-abdominal surgery, he/she can eat after 6 hours after surgery. If the patient is doing abdominal gastrointestinal surgery, usually can not eat a liquid diet until after the postoperative anal defecation, defecation.