BACKGROUND: Current guidelines recommend preoperative fasting of 2 h for clear fluids, which is often exceeded in routine clinical practice. Existing data on residual gastric volumes in children do not consider fluid intake within <2 h and rely on the aspiration of gastric contents via a gastric tube. This study evaluated the emptying of clear fluids from the stomach using magnetic resonance imaging (MRI).
METHODS: Healthy volunteers aged 6-14 years were asked to fast overnight. MRI scans to assess gastric volumes were obtained before and immediately after drinking 7 ml kg(-1) of diluted raspberry syrup and then every 30 min up to 120 min. Volumes were determined by a blinded investigator and indexed gastric fluid/air volumes (GFV(w)/GAV(w)) and half-life (t(1/2)) of GFV(w) course after clear fluid intake were calculated.
RESULTS: Sixteen children, median age 9.2 (range 6.4-12.8) years, were investigated. Median (range) GFV(w) was 0.62 (0.15-0.97) ml kg(-1) before and 6.68 (4.77-7.78) ml kg(-1) immediately after fluid intake, and 2.92 (0.43-5.04), 1.27 (0.28-3.62), 0.42 (0.07-2.49), and 0.32 (0.04-1.13) ml kg(-1) 30, 60, 90, and 120 min thereafter. Median GFV(w) declined exponentially (t(1/2)=26.1 min). Median individual t(1/2) was 23.6 (range 17.9-47.8) min. GAV(w) showed considerable intra- and inter-individual variation.
CONCLUSIONS: In healthy school children, gastric emptying after ingestion of clear fluid occurs with a median half-life time of <30 min but with considerable inter-individual variation.