[Preoperative fasting 2008: medical behaviour between empiricism and science].

Preoperative fasting aims at minimizing the risk of pulmonary aspiration. However, perioperative safety does not directly increase with the duration of total abstinence from food and liquids. The traditional principle "nil per os from midnight on", is based on insufficient data, overinterpretation and expert opinion. In fact, the total perioperative risk of a clinically relevant regurgitation of gastric content is low. Clear liquids are not stored within the stomach for a long time and in the healthy, a fasting period of 6 h allows the total passage of solid food. Identifying those patients with an increased risk of perioperative aspiration is still difficult. In particular, the impact of pregnancy, adipositas and diabetes, trauma, smoking, opioids and renal insufficiency has not been clarified. This lack of knowledge is reflected by national and international guidelines concerning preoperative fasting, which mention the "patient at risk" without defining it exactly. Abstention from clear liquids 2 h before and of solids 6 h before induction of anesthesia, is becoming increasingly more accepted. Feeding babies with breast milk appears to be tolerated 4 h before anesthesiological procedures.