Development of a modified formula for ultrasound assessment of gastric volume to determine the risk of aspiration: a prospective observational study
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INTRODUCTION: Ultrasound determination of aspiration risk based on the volume of stomach contents has been proposed for the patient's position on the right side (position 90), but not all patients can be turned on their side. OBJECTIVE: to develop a formula for ultrasound assessment of stomach volume for the patient's position with the head end raised by 300 and rotated to the right by 300 (position 30/30). MATERIALS AND METHODS: The prospective observational study included 150 patients. Ultrasound examination (ultrasound) of the antrum of the stomach was performed in the 30/30 position and on the right side. The formula was developed using a linear regression model RESULTS: Of the 150 patients, 22 were excluded (n=4 - inability to visualize, n=18 – heavy food). Age, weight ("weight"), height, BMI, circumference of the gastric trace ("circle") and the antrum of the stomach ("area") at the 30/30 position became predictors. The Pearson correlation revealed a strong positive association with the predictors "circle" (r=0,868) and "area" (r=0,901), a moderate inverse relationship with age (r=-0,319) and a weak direct relationship with weight (r=0,182). The step-by-step regression allowed us to select the model with the highest value of R2=0.850, which explained 85% of the total data set. A new formula for calculating the volume of gastric contents at position 30/30: Volume=110,29+21,874×Area-1,605×Age-1,148×Weight. Despite drinking 200 ml of warm liquid, the estimated volume of the stomach in the right-side position according to the A. Perlas formula was 42,02 (14,39; 185,39), and in the 30/30 position according to the modified formula 58,66 (16,87; 193,43) (p=0,451). СONCLUSION: The developed method of modified ultrasound assessment of stomach volume in the patient's 30°/30° position on the operating table has a high diagnostic value comparable to the well-known A. Perlas method on the right side.
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