[Fasting Recommendations Throughout the Ages].

When anaesthesia was in its infancy, the purpose of preoperative fasting was to prevent nausea and vomiting. In these early days of anaesthesia, liquid fasting periods were kept short to avoid exhaustion. The later introduction of the 'nothing by mouth after midnight' rule aimed to prevent aspiration. For decades, no distinction was made between clear liquids and solids. However, as studies could not demonstrate a difference in gastric residual volume when consuming clear liquids within the last 2-4 hours versus fasting for over 4 hours, the guideline recommendation regarding clear liquids was reduced to 2 hours by the end of the last century. As solid food remains in the stomach for longer, fasting periods of 6-8 hours are required. These should be adapted according to the type of food and the characteristics of the patient. However, periods of liquid fasting often exceed the recommended 2 hours, with a median duration of 9-12 hours. This can lead to dehydration, insulin resistance, and postoperative complications. As clear liquids leave the stomach quickly, an international, multidisciplinary consensus statement recommends implementing institutional protocols to minimise preoperative fasting times for liquids. These protocols can either encourage patients to drink clear liquids up to 2 hours before anaesthesia is induced or allow for liberal liquid fasting times.