[Preoperative fasting regimens and premedication to reduce the risk of pulmonary aspiration]

Our greater understanding of gastric physiology and the epidemiology of Mendelson's syndrome has allowed the traditional guidelines for preoperative fasting (nothing by mouth after midnight or 6 hours before surgery) to be changed, based on the results of many scientific studies. The stomach is not emptied of liquids and solids in the same way, and therefore preoperative fasting should not be the same for both. Human milk leaves the stomach more rapidly than infant formulas, and the emptying of non-human milk is similar to that of solids. Fasting does not guarantee that the stomach will be empty or that the pH of gastric juices will be high; moreover, shortening the preoperative fasting period may bring several advantages for the patient. Factors such as premedication, anxiety, age, certain associated diseases or injuries may or may not influence gastric emptying and/or acidity at the time of anesthesia. We review the literature, including the guidelines on fasting of the American Society of Anesthesiologists for application with healthy patients of all ages in elective procedures, excluding, among others, women in childbirth and patients undergoing emergency surgery.