Is jelly a solid or a clear liquid? A pilot study using ultrasound to assess the gastric emptying of fruit-flavoured gelatin dessert.

Pre-anaesthesia fasting guidelines typically recommend a six-hour fast for solids and a two-hour fast for clear liquids. Jelly is a fruit-flavoured gelatin dessert that exists as a viscoelastic semi-solid mass when refrigerated but melts back into its liquid form once ingested; therefore, it is not obvious to which category it should belong. We used ultrasound to investigate gastric emptying following ingestion of jelly in a pilot study of 10 fasted healthy adult volunteers. First, a baseline scan was performed to confirm their estimated gastric volume was less than 2.3 ml/kg (the 95th centile for a fasted population). Subjects then ate 400 g of jelly and underwent repeated scans every 10 minutes until their estimated gastric volume had returned to baseline. Median (interquartile range) estimated gastric volume was 0 (0-0.6) ml/kg at baseline, peaked at 3.1 (2.7-4.3) ml/kg 10 minutes post-ingestion and had decreased to 0 (0-0.9) ml/kg by two hours. It took a median (interquartile range) of 70 (47.5-80.0) minutes for estimated gastric volume to fall below 2.3 ml/kg, and 110 (110-130) minutes before it had returned to baseline. These data suggest that, for serving sizes up to 400 grams of jelly there might be no justification for mandating a six-hour fast prior to anaesthesia.