Ultrasonographic Assessment of Gastric Residual Volume

Data collection and measurements: The following clinical parameters of included patients will be recorded: age, sex, body weight, height, body mass index, Acute Physiology and Chronic Health Evaluation II (APACHE II) score on the day of admission,the Charlson Comorbidity Index score, any comorbid diseases, the total amount of EN product during the last 24 hours before ultrasonographic assessment, vasopressor therapy during imaging, and the dose of the vasopressors. Ultrasonographic gastric antrum imaging procedure: Ultrasonographic gastric antrum imaging will be carried out by the same intensivist on each patient just before routine tube-feed aspiration. Gastric antrum images will be obtained with a 2.5-6 MHz curvilinear probe placed in the sagittal plane of the epigastric region. All imaging attempts will be carried out in a 30-degree head-elevation supine position as described previously. Reference points will be used to obtain images of the gastric antrum-left anterior lobe of the liver, head of pancreas and abdominal aorta.The anteroposterior and craniocaudal diameters of the gastric antrum will be measured three times for each ultrasonographic assessment. The mean value of the three will be recorded. The universally accepted Two-Diameter Method defined by Bolondi et al. will be used for the measurement of antral cross-sectional area. Tube-feeding aspiration (GRV measurement) procedure: Routine gastric residual volume aspirations will be performed by the nursing staff blinded to the ultrasonographic measurements. The time between gastric antrum imaging and the beginning of GRV aspiration will be recorded in minutes. Gastric contents will slowly aspirated with 50 ml syringes for at least 10 minutes until stomach contents could no longer be aspirated. Patients will be reassessed with ultrasonography after the aspiration to ensure that the stomach is completely emptied with aspiration.