BACKGROUND AND AIMS: Commercially available high-calorie drinks containing fat and protein can be used as dietary supplements in surgical patients. According to preoperative fasting guidelines, high-calorie drinks are non-clear fluids and should not be consumed 6 h before elective procedures. The aim of this study was to evaluate the gastric emptying time of commercially available high-calorie drink formulations in healthy adults using gastric ultrasound.
METHODS: 25 healthy adult volunteers were included in this double-blind, cross-over prospective study. On three study sessions, fasted volunteers ingested one of the three study products: a solution of 75 g of glucose in 200 ml of water, a fat-free liquid meal, and a nutritionally complete liquid meal with equal volume and energy content. Gastric ultrasound examinations were performed to evaluate the gastric contents qualitatively and the volume of the gastric contents was calculated from the cross-sectional area of the gastric antrum measured in right lateral position by using a validated model. Repeated gastric ultrasounds were performed at baseline and half-hourly after ingesting the products in supine and right lateral position until the criteria for an empty stomach were met.
RESULTS: The glucose solution and the standard fat-free high-calorie drink with the same caloric content had a median gastric emptying time of 150 min. The nutritionally complete liquid meal had a median gastric emptying time of 180 min. Gastric emptying was complete in all participants before 6 h had elapsed since ingesting the study products.
CONCLUSIONS: High calorie liquid meals have a gastric emptying time longer than the recommended fasting time for clear fluids, but shorter than the recommended fasting time for solids in healthy adults.