Some people may think that eating something before surgery is the only way to have the strength to survive the surgery and anesthesia, unfortunately, this perception is wrong, eating or drinking will only lead to the cancellation or delay of the surgery. Anesthesiologists ask us if we have eaten must answer truthfully, especially patients admitted to the hospital in an emergency, doctors and nurses do not know whether they have eaten before patients, if lying about the time of eating, the price to pay may be life. Because after anesthesia if there is food in the stomach, vomiting may occur, vomiting that occurs after anesthesia, it is very easy to cause air to accidental aspiration, the consequences may be fatal! The usual situation except for local anesthesia, before receiving all anesthesia, must be fasting, abstain from drinking, that is to say, neither eat anything, nor drink anything, including water, the above-mentioned bun milk is even more can not be. Why do doctors let patients starve for surgery and anesthesia? When we are awake, we have various physiological reflexes to protect our airway from “water”, but after anesthesia, many physiological reflexes disappear and do not protect themselves, especially after general anesthesia, the patient is unconscious and can only rely on doctors and instruments for monitoring. Therefore, it is necessary to fast from food and water for 4-6 hours before surgery to ensure that the stomach is empty and that no vomiting or aspiration occurs during surgery. Swallowing reflex: Swallowing is a very fine and complex and ingenious reflex action that ensures that when eating and drinking, food enters the stomach along the esophagus and does not enter the trachea. Cough reflex: It can protect the foreign body that accidentally enters the airway. A small part of water enters the tracheobronchial tube, or water chokes into the lungs, and there are very sensitive receptors on the tracheobronchial tube, which once stimulated by water or other foreign bodies, immediately trigger the cough reflex to clear the foreign body inside. In addition, in the physiological state, the lower esophageal sphincter at the junction of the esophagus and stomach acts as a gate to prevent the reflux of food and stomach acid from the stomach back into the esophagus and mouth. Once anesthetized, the above three protective physiological functions are disrupted: (1) the lower esophageal sphincter is relaxed and does not function as a gate, and the stomach contents return to the esophagus and the mouth. (ii) The swallowing reflex is disrupted, and food may enter the lungs as long as it is present in the pharynx. (iii) The cough reflex is suppressed, and foreign bodies entering the trachea cannot be cleared out by the cough reflex. The consequence of airway aspiration is that food and gastric acid enter the lungs, resulting in immediate death by asphyxiation in severe cases and death or aspiration pneumonia within a few weeks in mild cases. Also during gastrointestinal surgery, the gastrointestinal tract generally needs to be emptied in order to ensure a smooth operation, which requires an even longer fast. Of course, the doctor will not let the patient starve, in the fasting and water phase, the doctor will provide energy (usually glucose) to the patient through the infusion, so most people will not starve down, individuals may have the feeling of an empty stomach, but for the safety of surgery stomach inside empty is necessary.