Developing a method for ultrasound estimation of gastric volume in patients with previous gastric sleeve

Ultrasound estimation of gastric volume is useful preoperatively for identifying those at increased risk of aspiration; however, studies to date have excluded subjects with prior gastric surgeries. We aimed to assess the performance of the current equation used in non-pregnant adults for patients who had undergone gastric sleeve and develop a new equation for this population if necessary. Secondarily, we determined if a 2-hour fast from clear fluids is sufficient to empty the stomach in this population.

37 subjects who had undergone a gastric sleeve in the last 10 years were randomly assigned to drink 100, 200 or 300 mL of water after fasting 8 hours from solids and 2 hours from clear fluids. Pre-drink and 0, 30, 60, 90 and 120 min post-drink scans measured antral grade and cross-sectional area. Subjects participated in up to three study visits drinking different volumes.

The existing equation was statistically suboptimal. A new equation was created with variables identified by LASSO regression (Volume (mL)=15.5×CSA (cm²)-0.28×Weight (kg)-0.75×Height (cm)+97.9) with a mean bias of <1 mL (95% limits of agreement -51.2 to 51.2 mL). After 120 min, 93.2% of post-drink scans were grade 0, and all had a calculated volume <1.5 mL/kg.

The existing equation is likely still best suited for clinical use; however, the equation proposed here has superior accuracy in patients with prior gastric sleeve. A 2-hour fast from clear fluids is sufficient in this population.