GLP1 Fasting Status and Gastric Retention Using Gastric Ultrasound

An Observational Study to Examine Non-inferiority of the Standard ASA Fasting Guidelines Versus 24-hour Clear Liquid Diet for Gastric Volume in Patients Taking GLP-1 Agonists

This study will enroll patients 18 years and older who are taking a GLP-1/GIP medication and 1) are scheduled for elective surgery and meet ASA fasting guidelines (nothing by mouth for at least 8 hours prior), or 2) scheduled elective colonoscopy and have been on a clear liquid diet for at least 24 hours prior. Participants will have a gastric ultrasound prior to surgery to measure any retained gastric contents. The purpose of this study is to determine if people taking GLP-1 receptor agonists and who fast normally are at an equal risk for having retained gastric contents after appropriately fasting for surgery, compared to patients who are on a liquid only diet for 24 hours prior to surgery.

Study Overview

• Status: Recruiting
• Conditions: Gastric Retention
• Intervention / Treatment: Diagnostic test: Gastric Ultrasound

Detailed Description

Patients will be classified into one of two groups:

1. Taking a GLP-1/GLP-GIP medication and undergoing an elective colonoscopy and have been on a clear liquid diet for the past 24-hours.

   or

2. Taking a GLP-1/GLP-GIP medication and undergoing am elective surgery and have fasted appropriately according to ASA guidelines.

All participants will undergo a gastric ultrasound in the preoperative area prior to their scheduled procedure. This will be completed to determine the amount of retained gastric contents, if any, after fasting properly prior to the procedure. An anesthesiologist attending who is properly trained on performing gastric ultrasounds and listed as a study team member will be the one performing the scan.

The patient will be placed in supine position. A curvilinear ultrasound probe will be placed on the sagittal plane below the xiphoid process. The probe will then slide along the costal margin to the right until the gastric antrum is identified. At this point, the ultrasound image will be obtained, and appropriate measurements will be taken. The patient will be placed in the right lateral decubitus position (RLD), and the above procedure will be repeated. The measurement of gastric antral cross-sectional area while in the RLD position will be recorded and used to calculate the gastric volume.

If based on the formula: GV (mL) = 27.0+(14.6*CSA)-(1.28*age) the patient is shown to have a gastric volume greater than 1.5mL/kg, or Antral Grade 2, the anesthesiologist assigned to the case will be alerted and will determine whether or not it is safe to continue with the scheduled surgery as the risk for aspiration may be higher based on the gastric ultrasound results.

Qualitative grading of the appearance of the gastric antrum in RLD will be graded as follows:

• Grade 0 antrum appears empty in both positions, and suggests no gastric content is present.
• Grade 1 antrum appears empty in the supine position, but clear fluid is visible in the RLD, consistent with a small volume of gastric fluid.
• Grade 2 antrum is that in which clear fluid is evident in both patient positions, or any solids in any position which is consistent with a higher volume state.

• Study Type: Observational
• Enrollment (Estimated): 150

Contacts and Locations

• Study Contact: Name: Haley Nitchie, MHA; Phone Number: 843-792-1869; Email: nitchie@musc.edu

Study Locations

• United States
  • South Carolina
    • Charleston, South Carolina, United States, 29425
      • Recruiting
      • Medical University of South Carolina
      • Contact: Haley Nitchie, MHA; Phone Number: 843-792-1869; Email: nitchie@musc.edu
      • Principal Investigator: Christopher Wolla, M.D.

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

This study will consist of patients who have taken a GLP-1 or GLP-GIP agonist medication within the past 30 days, and are scheduled for either an elective surgery and appropriately NPO for at least 8 hours prior, or scheduled for elective colonoscopy and have been on a clear liquid diet for at least 24 hours prior.

Description

Inclusion Criteria:

• Age 18+
• Have taken a GLP-1 or GLP-GIP agonist medication within the past 30 days
• ASA Physical Classification Status 1-3

• Fall into one of the following groups:

  1. Scheduled elective surgery and meet ASA fasting guidelines (NPO for at least 8 hours prior)
  2. Scheduled elective colonoscopy and have been on a clear liquid diet for at least 24 hours prior

Exclusion Criteria:

• Previous gastric or esophageal surgery
• Abnormal gastric anatomy
• Pregnancy
• Unable to provide written, informed consent
• Non-English speaking

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
ASA fasting guidelines; Scheduled elective surgery and meet ASA fasting guidelines (NPO for at least 8 hours prior)	Diagnostic test: Gastric Ultrasound; All participants will undergo a gastric ultrasound in the preoperative area prior to their scheduled procedure. The patient will be placed in supine position. A curvilinear ultrasound probe will be placed on the sagittal plane below the xiphoid process. The probe will then slide along the costal margin to the right until the gastric antrum is identified. At this point, the ultrasound image will be obtained, and appropriate measurements will be taken. The patient will be placed in the right lateral decubitus position (RLD), and the above procedure will be repeated. The measurement of gastric antral cross-sectional area while in the RLD position will be recorded and used to calculate the gastric volume.
24-hour clear liquid diet; Scheduled elective colonoscopy and have been on a clear liquid diet for at least 24 hours prior	Diagnostic test: Gastric Ultrasound; All participants will undergo a gastric ultrasound in the preoperative area prior to their scheduled procedure. The patient will be placed in supine position. A curvilinear ultrasound probe will be placed on the sagittal plane below the xiphoid process. The probe will then slide along the costal margin to the right until the gastric antrum is identified. At this point, the ultrasound image will be obtained, and appropriate measurements will be taken. The patient will be placed in the right lateral decubitus position (RLD), and the above procedure will be repeated. The measurement of gastric antral cross-sectional area while in the RLD position will be recorded and used to calculate the gastric volume.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pre-operative gastric volume per unit of weight (ml/kg) as assessed by gastric ultrasound.	While the patient is in supine position, the gastric volume will be measured via ultrasound and then calculated using a validated formula, GV (mL) = 27.0+(14.6*CSA)-(1.28*age).	From enrollment until completion of pre-operative gastric ultrasound (typically within 3 hours of scheduled procedure).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Perlas antral grade	Qualitative grading of the appearance of the gastric antrum in right lateral decubitus (RLD) will be graded as follows:1; Grade 0 antrum appears empty in both positions, and suggests no gastric content is present.; Grade 1 antrum appears empty in the supine position, but clear fluid is visible in the RLD, consistent with a small volume of gastric fluid.; Grade 2 antrum is that in which clear fluid is evident in both patient positions, or any solids in any position which is consistent with a higher volume state.	From enrollment until completion of gastric ultrasound (within 3 hours of scheduled procedure).
Incidence of full stomach on gastric ultrasound assessment	Incidence of full stomach defined as solid or thick liquids on US or >1.5mL/kg of clear liquid upon gastric ultrasound.	From time of enrollment until the start of surgery, up to 24 hours.
Incidence of regurgitation under anesthesia		From induction of anesthesia until end of surgery (up to 8 hours).
Incidence of change in anesthetic management based on stomach contents		Assessed at enrollment and during gastric ultrasound (within 3 hours of scheduled procedure).
Differences in "high risk GLP-1" vs "low risk GLP-1"	High Risk includes: Escalation Phase: increase in dose within the past 30 days; High Dose; Weekly Dosing; Presence of severe GI symptoms such as nausea, vomiting, or retching, abdominal bloating, or abdominal pain with GLP-1 administration Low dose and high dose are classified as: Oral Semaglutide (Rybelsus) Low dose: < 5 mg High dose: > 5 mg Tirzepatide (Mounjaro and Zepbound) Low dose: 2.5, 5, and 7.5 mg High dose: 10, 12.5, 15 mg SubQ Semaglutide (Ozempic and Wegovy) Low dose: 0.25 and 0.5 mg High dose: 1 and 2 mg Dulaglutide (Trulicity) Low dose: 0.75 and 1.5 mg High dose: 3.0 and 4.5 mg Liraglutide (Victoza) Low dose: 0.6 mg High dose: 1.2 and 1.8 mg Exenatide (Byetta) Low dose: 5 mcg High dose: 10 mcg	assessed at time of enrollment from the past 30 days until completion of gastric ultrasound

Collaborators and Investigators

• Sponsor: Medical University of South Carolina
• Investigators: Principal Investigator: Christopher Wolla, M.D., Medical University of South Carolina

Study record dates

Study Major Dates

• Study Start (Actual): February 3, 2026
• Primary Completion (Estimated): December 31, 2026
• Study Completion (Estimated): December 31, 2026

Study Registration Dates

• First Submitted: November 11, 2025
• First Submitted That Met QC Criteria: November 24, 2025
• First Posted (Actual): November 26, 2025

Study Record Updates

• Last Update Posted (Actual): February 25, 2026
• Last Update Submitted That Met QC Criteria: February 24, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: Pro00147318

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No