The first doctor to perform surgery. The patient must be anesthetized in order to not have to endure the pain during the surgery. And hence If the patient abstain from water and food before. It may be that the patient is choking debris. Or gastric juice in the stomach reflux up into the lungs.
The violence is very different depending on the type and quantity of food aspiration. If severe hypoxia may cause patients or patients with respiratory problems. Therefore, no water, no food before surgery should be the best.