What follows are highlights from these studies:

Association of GLP-1 Receptor Agonist Medication Duration of Use and Withholding Time with Predicted Probability of Preoperative Full Stomach

GLP-1 receptor agonists, including medications commonly prescribed for diabetes and weight management, can delay gastric emptying, raising concerns that patients may still have food or liquid in their stomach at the time of surgery. This can increase the risk of aspiration, a potentially serious complication during anesthesia.

In a multicenter study, researchers examined whether GLP-1 receptor agonist use and medication withholding times were associated with the likelihood of a full stomach before surgery. While patients taking GLP-1 medications had slightly higher rates of a predicted full stomach than those not taking the medications, the difference was smaller than expected. Researchers noted that prolonged fasting before surgery may have contributed to the findings, though fasting alone did not eliminate the risk, as some full-stomach patients in the GLP-1 group had fasted for more than 23 hours.

"As concerns have grown about delayed gastric emptying in patients taking GLP-1 medications, many clinicians have looked to longer fasting times as a potential strategy to reduce risk," said Oliver Panzer, MD, anesthesiologist at HSS and co-author of the study. "Our findings suggest that extended fasting may help reduce the likelihood of a full stomach, but it is unlikely to eliminate the risk entirely. However, because this was an observational study, we cannot conclude that longer fasting times directly caused the lower rates of full stomach observed in some patients. Additional research is needed to better understand the factors that influence gastric emptying and perioperative risk in patients taking GLP-1 medications."

Interrater Reliability of Preoperative Gastric Ultrasound in Patients Using Cannabis

Gastric ultrasound is increasingly used before surgery to help determine whether a patient's stomach is empty or still contains food or fluid that could increase aspiration risk during anesthesia. Although established guidelines exist for interpreting these ultrasound images, researchers found that assessing stomach contents in patients who use cannabis may be more challenging than expected.

The study's key finding was poor agreement among four experienced point-of-care ultrasound clinicians reviewing gastric ultrasound images, suggesting that existing ultrasound criteria may not always provide clear guidance in patients who use cannabis. One potential challenge is the presence of air in the gastric antrum, which can appear in both empty and full stomachs and may complicate interpretation.

“We found considerable variation among experienced clinicians reviewing the same ultrasound images," said Stephen Haskins, MD, anesthesiologist at HSS and co-author of the study. "The findings suggest that additional refinement of gastric ultrasound criteria may be needed to improve consistency, reduce uncertainty, and support clearer perioperative decision-making."

Implications for Preoperative Decision-Making

Together, these studies underscore the growing complexity of preoperative stomach assessment as patient populations and medication-use patterns evolve. The GLP-1 study suggests that longer fasting periods may help reduce the risk of a full stomach before surgery, though fasting alone may not completely eliminate risk. Meanwhile, the cannabis study highlights potential limitations in current gastric ultrasound criteria.

Collectively, the findings suggest that assessing aspiration risk may require a more individualized approach and that additional research is needed to refine the tools and guidelines clinicians use to make perioperative decisions. Researchers hope the studies will help inform future efforts to improve patient safety and anesthesia care.

“As GLP-1 medications increase in popularity, the effect of these drugs in patients undergoing surgery raises concerns for anesthesiologists,” says Oliver PF Panzer, MD, anesthesiologist at HSS and author of both studies. “We seek to better understand the usage and impact of GLP-1s on patients undergoing surgery so we can adapt the management of these patients to maximize their safety.”

Study: Cross Sectional Assessment of Preoperative Gastric Content with Ultrasound in Patients Taking GLP-1 Agonists

In the study “Cross Sectional Assessment of Preoperative Gastric Content with Ultrasound in Patients Taking GLP-1 Agonists,” researchers set out to explore how GLP-1 medications affect gastric emptying in patients scheduled for surgery. Food retained in the stomach can increase the risk of regurgitation and pulmonary aspiration of gastric contents, a serious, life-threatening complication during general anesthesia.

“Previous studies show patients using the GLP-1 agonist semaglutide (Ozempic, Wegovy, and Rybelsus) experience slower gastric emptying, which can result in residual gastric contents even when these patients follow standard preoperative fasting guidelines,” says Dr. Panzer. “We became concerned that patients taking GLP-1s may not be adequately protected from aspiration during anesthesia under the current guidelines.”

“The goal of this study was to look at the incidence of full stomach in patients taking GLP-1s compared to patients not taking the drugs,” says Dr. Panzer. “We also wanted to look at fasting times to detect whether people on GLP-1s who fast longer than the guidelines recommend trend toward being less full.”

In the multi-center, prospective, cross-sectional observational study, researchers used ultrasound to assess the preoperative incidence of full stomach in elective surgery patients taking weekly injectable GLP-1s compared to elective surgery patients not taking the drugs. A total of 354 patients were included in the study between August 29, 2023, and January 31, 2025. Ultrasound was performed by an anesthesiologist in the preoperative holding area, with clear fluid >1.5ml/kg or solid content indicating a full stomach. All institutions followed American Society of Anesthesiology “nothing by mouth” (NPO) fasting guidance (8 hours for heavy fatty foods; 6 hours for light meals; 2 hours for clear liquids).

Dr. Panzer and colleagues found no significant difference in the incidence of full stomach between patients taking GLP-1s and those who do not. Overall fasting times for solids tended to be longer in full patients in the GLP-1 group compared to the control group (23.73 vs 16.63 hours) but did not reach statistical significance.

“This multicenter study showed no difference in the rate of full stomachs between the GLP-1 group and the control group, which stands in contrast to what most studies have shown so far,” says Dr. Panzer. “One possible explanation for our result is that our patients report higher average fasting times (18.5 hours) than patients at other institutions. However, there may be other factors that warrant further investigation.”

“We hope to follow up this study with research that examines whether 24 hours of solid food fasting is helpful in reducing full stomach in patients on GLP-1s,” says Dr. Panzer. “Another question is whether pausing GLP-1s prior to surgery may have an impact on full stomach. Although the current guidance says to continue taking GLP-1s before surgery because stopping the drug poses its own health risks, it’s a question worth exploring.”

Study: Institutional Trends in GLP-1 Agonist Use Among Hip and Knee Arthroplasty Patients, 2021–2024

In the study, “Institutional Trends in Glucagon-Like Peptide-1 Receptor Agonist Use Among Hip and Knee Arthroplasty Patients, 2021–2024,” researchers explore the prevalence of glucagon-like peptide-1 (GLP-1) agonist use among patients undergoing primary and revision total hip arthroplasty (THA) and total knee arthroplasty (TKA) at HSS.

“As usage of GLP-1s continues to expand in the general population, we wanted to capture the incidence and type of GLP-1 usage among patients undergoing hip and knee arthroplasty,” says Dr. Panzer.

The researchers retrospectively reviewed the records of 45,537 adult patients who underwent primary or revision THA or TKA between January 4, 2021, and December 31, 2024. Dr. Panzer and colleagues found GLP-1 use increased significantly in that period, rising from 3.69% in 2021 to 12.84% in 2024.  Semaglutide and tirzepatide were the most common agents, accounting for 88% of all GLP-1 use in 2024. Higher rates of GLP-1 use were seen in patients with significant comorbidities such as hypertension, diabetes, or heart failure, and in Black patients.  

“We also saw a significant decrease in the number of GLP-1 users with diabetes in this time period, suggesting that more patients are using these medications for other reasons such as weight loss,” notes Dr. Panzer.

“We will continue to examine GLP-1 usage in the surgical orthopedic population so we can ensure patients on these drugs can have surgery safely,” says Dr. Panzer. “We’re just at the beginning of this investigative journey, so there is a lot more insight to come.”

These studies contribute important early evidence to help guide emerging perioperative considerations for patients using GLP‑1 medications.

References:

Study 1: Cross Sectional Assessment of Preoperative Gastric Content with Ultrasound in Patients Taking GLP-1 Agonists

Authors: Oliver Panzer, Maya Tailor, Juliet E. Rowe, Michael Singleton, William Manson, Hari Kalagara, Nibras Bughrara, Anahita Dabo-Trubelja, Marissa Weber, Eric Heinz, Stephen C. Haskins, William P. Qiao, Miriam Sheetz, Alex Illescas, Kayla Bernstein, Mariel Maramba, Mahtab Sheikh, Jayanta Chowdhury, Sheila Carr, Tatum Gee, Eduard Shaykhinurov, Justas Lauzadis, Jashvant Poeran, Anahi Perlas

Study 2: Institutional Trends in Glucagon-Like Peptide-1 Receptor Agonist Use Among Hip and Knee Arthroplasty Patients, 2021–2024

Authors: Juliet Rowe, Maya Tailor, Alexandra Sideris, Alex Illescas, Jawad Saleh, Jashvant Poeran, Daniel Maalouf, Oliver Panzer