Preoperative fasting for the infusion of “yerba mate”: a randomized clinical trial with ultrasound evaluation of gastric contents

BACKGROUND: The traditional infusion of “yerba mate” is widely consumed in South America and exported to countries around the world. Although generally considered a “clear fluid”, there is no data to date on the gastric emptying time of yerba mate and safe preoperative fasting intervals. The objective of this study was to evaluate the gastric emptying time of a standardized infusion of yerba mate using bedside ultrasound and compare it with the time confirm of hot and cold tea. METHODS: This was a prospective, randomized crossover experimental study. Thirty healthy volunteers were evaluated after 8 hours of fasting for both fluids and solids. Gastric antral area and gastric volume were evaluated at baseline and every 20 minutes after drinking 300 mL of randomly assigned infusion of “yerba mate”, hot tea, or cold tea. RESULTS: The mean gastric emptying time was: 69.7 ± 22.1 min, 63.1 ± 14.5 min, and 64.3 ± 23.5 min for the mate, hot tea, and cold tea respectively. No significant differences were found in emptying time among the infusion groups (p-value = 0.043). When same time measures were compared, the only significant difference detected was between hot teas and mate infusion at 20 minutes (p-value = 0.012) CONCLUSION: Yerba mate infusion has a similar gastric emptying time to that of tea. All subject's gastric volume returned to baseline values by 100 minutes. It is reasonable to recommend a similar fasting period of 2 hours for mate infusion prior to elective surgery.