Full Stomach Status

Introduction Obesity and type 2 diabetes mellitus constitute a global public health problem. Medications with glucagon-like peptide-1 (GLP-1) receptor agonist activity are a modern therapeutic option for both diseases. Liraglutide, semaglutide, dulaglutide and tirzepatide are representatives of this drug class, whose mechanism of action results in delayed gastric emptying, reduced gastric motility and increased gastric volume. Tirzepatide, however, presents a dual agonist action, combining GLP-1 agonism with glucose-dependent insulinotropic polypeptide (GIP) agonism. The presence of gastric content during anaesthesia may lead to pulmonary aspiration and the development of chemical pneumonitis, a potentially devastating complication. However, when there is a risk factor for delayed gastric emptying, despite adequate fasting, the stomach may still present residual content, and bedside ultrasonography is an effective, non-invasive and rapid method to measure this content and stratify aspiration risk. Our hypothesis is that most individuals using tirzepatide present a full stomach even after fasting times recommended in the literature.

This is a prospective, single-center observational study conducted at the Fribourg Cantonal Hospital to evaluate the diagnostic performance of preoperative gastric ultrasound in determining gastric content and volume. Upper gastrointestinal endoscopy with complete suction of gastric contents serves as the reference standard. Adult patients (≥ 18 years) scheduled for elective or urgent gastroscopy are consecutively recruited. A gastric ultrasound is performed within one hour before the endoscopic procedure. The antral cross-sectional area is measured in standardized positions (supine and right lateral decubitus), and gastric volume is estimated using validated formulas. Gastric content is categorized into three grades (empty, low-risk liquid content, or high-risk/solid content). During gastroscopy, complete aspiration of gastric contents is performed at the start of the procedure. The aspirated volume and qualitative characteristics (liquid vs. solid) are recorded, and the stomach is classified as empty, partially full, or full by the endoscopist. The primary objective is to determine the accuracy of gastric ultrasound in identifying a full stomach. Secondary objectives include evaluating the qualitative agreement between ultrasound and gastroscopy, correlating estimated gastric volume with aspirated volume, and identifying an optimal ultrasound-based volume threshold predictive of a full stomach. Approximately 1,390 patients will be enrolled over one year to obtain at least 139 "full stomach" cases, based on prevalence estimates and sample size calculations. Statistical analyses will include diagnostic performance metrics, Cohen's kappa, correlation tests, Bland-Altman plots, and ROC curve analysis.