[Ultrasound Dynamics of Gastric Content Volumes After the Ingestion of Coconut Water or a Meat Sandwich. A Randomized Controlled Crossover Study in Healthy Volunteers]

Background: Adequate preoperative fasting is critical in preventing pulmonary aspiration of gastric content. We proposed to study the sonographic gastric content dynamics after the ingestion of liquid or solid food in healthy volunteers and confront it with current guidelines for preoperative fasting times.

Methods: We performed a prospective, crossover, evaluator-blinded study involving 17 healthy volunteers of both sexes. Each participant fasted for 10h and was subjected to a baseline gastric ultrasound, intake of 400mL of coconut water or a 145g, 355kcal meat sandwich, and sonographic gastric evaluations after 10min and every hour until the stomach was completely empty.

Results: At baseline, all subjects had an empty stomach. At 10min, gastric content [mean + standard deviation (SD)] was 240.4 + 69.3 and 248.2 + 119.2mL for liquid and solid foods, respectively (p>0.05). Mean + SD gastric emptying times were 2.5 + 0.7 and 4.5 + 0.9h for liquid and solid foods, respectively (p<0.001). For the drink, the stomach was completely empty in 59% and 100% of the subjects after two and four hours, and for the sandwich, 65% and 100% of the subjects after four and seven hours, respectively.

Conclusions: Sonographic gastric dynamics for coconut water and a meat sandwich resulted in complete gastric emptying times higher and lower, respectively, than those suggested by current guidelines for preoperative fasting.