Gastric volume – PO liquid effect

Preoperative fasting is used to reduce the risk of pulmonary aspiration. From the ASA guidelines on preoperative fasting, meta-analysis of randomized controlled trials demonstrated in adult patients given clear liquids 2-4 hours before a procedure versus 4 hours had smaller gastric volumes and higher pH values.  In children who received clear liquids 2-4 hours prior to a procedure versus fasting for >4 hours , meta-analysis of randomized controlled trials demonstrated only higher gastric pH values, but was equivocal regarding gastric volume.

In contrast, observational studies with ingestion of breast milk and infant formula 4 hours prior to a procedure were equivocal regarding higher gastric volumes or lower gastric pH.