With the exception of local anesthetics, anesthesia for elective surgery requires preoperative fasting and water fasting. However, the question of whether to fast is more complex and depends first on what kind of surgery is being performed. If it is a very urgent surgery, so urgent that there is no time to fast, the anesthesiologist will take special measures to prevent reflux aspiration by mistake, but this will inevitably increase the risk for the patient himself. To fully understand this issue, one must know why fasting is necessary. After anesthesia, people lose their instincts to protect themselves as follows: 1. Swallowing reflex: that is, if there is something inside the mouth, the patient cannot swallow it himself; 2. Vomiting reflex: that is, if there is something in the mouth, he cannot spit it out; 3. Choking reflex: after losing this reflex, if food is blocked in the trachea, he cannot cough it up. This situation can lead to choking even with a small amount of saliva, and can be even more dangerous if food is eaten. After anesthesia, a person’s esophageal sphincter relaxes, which increases the possibility of reflux. After eating, gastric acid is secreted in the stomach, and once food containing gastric acid enters the airway, it will strongly stimulate the airway, leading to tracheal spasm and inability to breathe, and in severe cases, damage to both the airway and lungs, aspiration pneumonia, etc., so it is more dangerous. In case of elective surgery, it is best to fast and abstain from food and water even with intralesional anesthesia as prescribed by the doctor.