Despite the abundance of evidence to the contrary, 6-8 hours of total preoperative fasting is still considered essential by many surgeons and anesthesiologists, based on the strength of old concepts. Patients frequently end up fasting for 12 hours or more because of delays and changes in operating room schedules. The metabolic response to long fasting leads to intensification of the organic response occurring after trauma, which is mainly manifested as increased insulin resistance, an acute-phase response, and loss of lean body mass. In fact, there has not been any evidence indicating that a shorter fast of 2-3 hours, which includes oral clear or carbohydrate (CHO)-rich (12.5% carbohydrates, 50 kcal/100 mL) fluids, results in an increased risk of aspiration, regurgitation, or related morbidity compared with the standard policy of "nil by mouth after midnight." In addition, preoperative treatment with CHO-rich fluids may reduce postoperative discomfort and, for patients undergoing major abdominal surgery, may decrease the duration of postoperative hospitalization. New formulas for preoperative oral fluids containing amino acid or protein such as glutamine or whey protein are also potential candidates for early preoperative treatment and merit further study.
Keywords: acute-phase proteins; carbohydrates; fasting; glutamine; insulin resistance; preoperative care; trauma; whey protein.