Effects of clear liquids on gastric volume and pH in healthy volunteers.

The effects of clear liquids on gastric volume and pH were examined in 30 healthy ASA physical status I volunteers. After overnight fasting, a Salem-sump nasogastric tube was inserted and gastric contents were removed for measurement of volume and pH. Gastric contents were then reinserted through the nasogastric tube into the stomach. The volunteers were randomly divided into three groups: group 1 (n = 10) received 240 mL water, group 2 (n = 10) received 240 mL coffee, and group 3 (n = 10) received 240 mL pulp-free orange juice. All liquids were administered orally. Gastric contents were then again aspirated, measured for volume and pH, and reinserted through the nasogastric tube every half hour until gastric volume was less than 25 mL. All volunteers had gastric volumes less than 25 mL with a slight decrease in pH within 2 h of orally taking one of the three 240-mL liquids. These data suggest that if patients have ingested a moderate amount of clear liquids it is safe to conduct general anesthesia after a 2-h fast in healthy surgical patients.