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 and eating or drinking will only lead to the cancellation or delay of the surgery. The price to pay for withholding food could be life! Because vomiting can occur if there is food in the stomach after anesthesia, vomiting that occurs after anesthesia can be fatal! Before receiving all anesthesia except local anesthesia, one must abstain from eating and drinking, which means that one can neither eat nor drink anything, including water, and the aforementioned bun and milk is even more impossible. Why do doctors let patients starve for surgery and anesthesia? Under physiological conditions, the lower esophageal sphincter at the junction of the esophagus and stomach acts as a gate to prevent food and stomach acid from returning to the esophagus and mouth. Swallowing is a very fine and complex and ingenious reflex action that ensures that when eating and drinking, food goes down the esophagus into the stomach and not into the trachea. If this reflex action is disrupted, for example, choking on water, it is because a small part of the water has entered the tracheobronchial tube, or the water has choked on the lungs. There are very sensitive receptors on the tracheobronchial tube, and once stimulated by water or other foreign bodies, the cough reflex is immediately triggered to clear the foreign body inside. Once anesthetized, the above three protective physiological functions are disrupted: 1. the lower esophageal sphincter is relaxed and does not act as a gate, and the stomach contents return to the esophagus and mouth. 2. the swallowing reflex is disrupted, and as long as there is food in the pharynx, it may enter the lungs. 3. the cough reflex is suppressed, and foreign bodies that enter the trachea cannot be cleared out by the cough reflex. The consequence is that food and stomach 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. In addition, during gastrointestinal surgery, the gastrointestinal tract generally needs to be emptied 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.