Many patients and their families do not understand or appreciate that they cannot eat or drink before surgery, and some even believe that they need to eat well before surgery in order to better “tolerate surgery” and that “surgery on a hungry stomach is unbearable”. As a result, sometimes patients or family members do not listen to the physician’s advice or forget the nurse’s instructions and eat before the surgery, and have to stop the surgery and do it again at a later date. So, why should eating and drinking be prohibited before surgery? This is mainly to prevent choking or aspiration pneumonia caused by vomiting reaction during anesthesia or surgery. This vomiting reaction may occur at any time during anesthesia, especially during tracheal intubation, suction tube aspiration, and catheter removal, because some anesthetic drugs attenuate the body’s normal protective reflexes. For example, the lungs have protective cough reflexes to stomach contents to prevent them from entering the lungs, but after anesthesia, these reflexes disappear. Stomach acid is very irritating to the lungs, and once it enters the lungs it often causes aspiration pneumonia, which can lead to respiratory failure and affect life. If anesthesia surgery is performed after eating or drinking a lot of water, the stomach contents can be vomited out before digestion into the intestine, which will not only affect the normal operation, but more importantly, these vomited things can easily reflux into the trachea or lungs under anesthesia to cause fatal asphyxia or aspiration pneumonia, which can even endanger the patient’s life in serious cases. So when should you start not eating or drinking before surgery? It depends on the site, type and size of the surgery and the age and general condition of the patient. Generally, eating and drinking should be prohibited 8-12 hours before surgery, and drinking should be prohibited from 4 hours. The reason for not drinking water after surgery is to avoid the occurrence of eruption, which is caused by surgical stimulation of the nerve center or the diaphragm. General anesthesia, epidural anesthesia, and lumbar anesthesia are not allowed to have water for six hours, and fluids will be replenished intravenously.