Data from study 'Ultrasonographic Assessment of Gastric Emptying Following Water Ingestion in Healthy Volunteers'

Current guidance on pre-operative fasting for clear fluids to reduce aspiration risk may result in unnecessary dehydration. Guidance and practice vary with more liberal fluid regimes currently being advocated. In this randomised single blinded crossover study we used an established ultrasound protocol to measure the gastric volume of 15 healthy volunteers following the 2011 European Society of Anaesthesia fasting guidelines (nil-by-mouth two hours before induction of anaesthesia) and the more liberal 2005 Scandinavian guidelines (150mL water with medication up to 1 h before induction of anaesthesia). We observed that gastric volumes increased following ingestion of water in all individuals compared to their fasted states. Water left the stomach within 30 minutes following ingestion in ten individuals, and within an hour in three individuals (gastric volume <1.5 ml.kg-1). A reduction in thirst was observed in the group allowed to drink water, whereas hunger and anxiety scores were unaffected. There was no difference in gastric volumes between regimes (p=0.8) at the earliest time the guidelines permitted induction of general anaesthesia. We observed that two individuals following the more conservative European Society of Anaesthesia guidelines were above the accepted safe gastric volume, in keeping with previous studies suggesting that around 5% individuals who would be considered fasted on current guidelines actually fall into a higher risk group for aspiration. The findings of this small feasibility study support the view that a reduction of fasting time for clear fluids prior to general anaesthesia is safe. Further studies need to replicate these findings in patients undergoing surgery.