The effects of the macronutrient and caloric content of oral solutions on gastric emptying time

Introduction / Purpose: ERAS recommends that clear liquids be consumed up to 2 hours prior to elective surgery. However, it has been observed that patients remain fasting for longer periods prior to surgeries, resulting in consequences such as dehydration, catabolic processes, and hemodynamic changes post-operatively. The effects of different types of nutrients on gastric emptying time maintain significant importance both in daily life and in clinical practices. In the literature, data regarding the effects of different macronutrients on gastric emptying are limited. The purpose of our study is to investigate the effects of oral macronutrient solutions and the caloric content of these liquids on gastric emptying time and to prevent prolonged preoperative fasting. Materials and Methods: Our study was prospectively conducted with 20 healthy volunteer participants at Koç University Hospital between July 15-30, 2024. Participants consumed 3 different macronutrients (Carbohydrates, Protein, Fat) in 2 different calorie groups (150 kcal and 300 kcal) over 6 different days. All measurements were taken at the same time. The cross-sectional area (CSA) of the gastric antrum was measured with a convex probe before and after the consumption of the solutions. After consuming the drinks, measurements were repeated, and the antrum CSA was measured at 15-minute intervals until it returned to the initial value. The time taken for the gastric antrum CSA to reach its initial value was recorded. Results: According to the results of the Friedman test, the gastric emptying time of the solution containing 150 kcal of carbohydrates was the shortest (30-75 minutes), while the gastric emptying time of the solution containing 300 kcal of fat was the longest (90-120 minutes). It was concluded that solutions containing 300 kcal from the same macronutrient group had significantly longer gastric emptying times compared to those containing 150 kcal. Discussion / Conclusion: The extension of the fasting period before surgery can lead to many intraoperative and postoperative hemodynamic, psychological, and metabolic consequences. To prevent this, we anticipate that patients can safely consume 350 ml of a carbohydrate-containing solution with 150 kcal up to 90 minutes preoperatively. We also observed that not only do gastric emptying times depend on the type of macronutrient, but solutions containing higher calories within the same macronutrient group empty from the stomach more slowly. We believe that recommendations for determining preoperative fasting periods should consider not only the type of macronutrient but also the caloric content. Keywords: ERAS, gastric ultrasound, calorie, macronutrient, preoperative fasting