HSS Studies Find Limits in Preoperative Stomach Assessment

Hospital for Special Surgery (HSS) announced on September 17, 2026, that two of its studies presented at the 2026 European Society of Regional Anaesthesia and Pain Therapy (ESRA) Congress found that current approaches to evaluating whether a patient’s stomach is empty before surgery may not always provide clear answers as GLP-1 medication and cannabis use become more common.

According to the HSS newsroom release, anesthesiologists are facing new questions about how best to assess stomach contents before surgery. Food or liquid retained in the stomach can increase the risk of aspiration, a potentially serious complication during anesthesia. The studies were presented at the 43rd ESRA Annual Congress, held at the Lisbon Congress Centre in Lisbon in September 2026; according to the congress organizers, accepted abstracts from the meeting are published in the Regional Anaesthesia and Pain Medicine journal.

GLP-1 Withholding Times and Full-Stomach Findings

GLP-1 receptor agonists, a class of medications commonly prescribed for diabetes and weight management, can delay gastric emptying, according to the release, raising concerns that patients may still have food or liquid in their stomach at the time of surgery.

In the multicenter study, titled “Association of GLP-1 Receptor Agonist Medication Duration of Use and Withholding Time with Predicted Probability of Preoperative Full Stomach,” researchers examined whether GLP-1 receptor agonist use and medication withholding times were associated with the likelihood of a full stomach before surgery. Patients taking GLP-1 medications had slightly higher rates of a predicted full stomach than those not taking the medications, but the difference was smaller than expected, HSS reported. The researchers noted that prolonged fasting before surgery may have contributed to the findings, though fasting alone did not eliminate the risk: some patients in the GLP-1 group who were found to have a full stomach had fasted for more than 23 hours.

“Our findings suggest that extended fasting may help reduce the likelihood of a full stomach, but it is unlikely to eliminate the risk entirely,” said Oliver Panzer, MD, an anesthesiologist at HSS and co-author of the study. Because the study was observational, he said, the team cannot conclude that longer fasting times directly caused the lower rates of full stomach observed in some patients, and additional research is needed to better understand the factors that influence gastric emptying and perioperative risk in patients taking GLP-1 medications.

Gastric Ultrasound Interpretation in Patients Using Cannabis

The second study, “Interrater Reliability of Preoperative Gastric Ultrasound in Patients Using Cannabis,” examined how consistently clinicians interpret gastric ultrasound images in this patient group. 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, and established guidelines exist for interpreting the images, HSS said.

The study’s key finding, HSS reported, was poor agreement among four experienced point-of-care ultrasound clinicians reviewing gastric ultrasound images in patients who use cannabis, suggesting that existing ultrasound criteria may not always provide clear guidance. One potential challenge identified by the researchers 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, an anesthesiologist at HSS and co-author of the study. He said the findings suggest that additional refinement of gastric ultrasound criteria may be needed to improve consistency, reduce uncertainty, and support clearer perioperative decision-making.

Taken together, the studies underscore the growing complexity of preoperative stomach assessment as patient populations and medication-use patterns evolve, according to HSS. The organization said 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. The researchers said they hope the studies will help inform future efforts to improve patient safety and anesthesia care.

The trials underlying the two presentations are registered on ClinicalTrials.gov as HSS-led observational studies, and neither registry record includes posted results. The GLP-1 trial, registered as NCT06003985 under the title “Assessment of Preoperative Gastric Content With Ultrasound in Patients Taking GLP1 Agonists,” is listed as an observational, cross-sectional cohort study with an actual enrollment of 354 patients. The registry shows a start date of August 29, 2023, and a primary completion date of January 31, 2025, with the study now marked completed. Eight sites are listed: Hospital for Special Surgery, Weill Cornell Medicine, and Memorial Sloan Kettering Cancer Center in New York; George Washington University Hospital in Washington, D.C.; Mayo Clinic in Jacksonville, Florida; Albany Medical Center in Albany, New York; the University of Virginia in Charlottesville; and University Health Network in Toronto, Canada. The registration defines a full stomach as solid food, thick liquids, or clear liquid measuring more than 1.5 milliliters per kilogram of body weight on ultrasound, and it enrolled adults taking once-weekly GLP-1 agonists, including semaglutide, dulaglutide, and tirzepatide, for any indication, alongside a control group not taking the drugs. Panzer is listed as principal investigator.

The cannabis trial is registered as NCT06567873 under the title “Assessment of Preoperative Gastric Content With Ultrasound in Patients Reporting Cannabis Use.” The registry describes an observational, cross-sectional cohort study conducted at Hospital for Special Surgery with an actual enrollment of 40 patients, a start date of May 9, 2025, and a completion date of October 14, 2025, also with Panzer as principal investigator. The study enrolled patients who reported cannabis use within one month of their surgery date and excluded patients taking GLP-1 agonists, among other conditions. Its primary outcome was the incidence of delayed gastric emptying, using the same full-stomach definition, with secondary outcomes including nothing-by-mouth intervals, gastric peristalsis, and the time since last cannabis use. The registry summary states that there is currently no adapted nothing-by-mouth guideline to account for cannabis use.

The September 17 announcement follows earlier HSS research on GLP-1 medications in surgical patients. At the American Society of Regional Anesthesia and Pain Medicine annual meeting in April 2026, HSS researchers presented a 354-patient multicenter cross-sectional study that used ultrasound to compare the incidence of full stomach in elective surgery patients taking weekly injectable GLP-1 medications with patients not taking them. All participating institutions followed American Society of Anesthesiology nothing-by-mouth fasting guidance of eight hours for heavy fatty foods, six hours for light meals, and two hours for clear liquids. HSS reported in April that the study found no significant difference in full-stomach incidence between the two groups. Fasting times for solids tended to be longer among full-stomach patients in the GLP-1 group than in the control group, at 23.73 versus 16.63 hours, but did not reach statistical significance. Panzer said one possible explanation for the contrast with earlier studies was a higher average fasting time of 18.5 hours among the study’s patients.

A companion study presented at the same meeting reviewed records of 45,537 HSS patients who underwent hip or knee arthroplasty between January 4, 2021, and December 31, 2024. HSS reported that GLP-1 use in that population rose from 3.69% in 2021 to 12.84% in 2024, with semaglutide and tirzepatide accounting for 88% of GLP-1 use in 2024.

Study citations:

• Hospital for Special Surgery, New York (principal investigator: Oliver Panzer, MD). “Assessment of Preoperative Gastric Content With Ultrasound in Patients Taking GLP1 Agonists.” ClinicalTrials.gov, NCT06003985, first posted August 22, 2023. https://clinicaltrials.gov/api/v2/studies/NCT06003985
• Hospital for Special Surgery, New York (principal investigator: Oliver Panzer, MD). “Assessment of Preoperative Gastric Content With Ultrasound in Patients Reporting Cannabis Use.” ClinicalTrials.gov, NCT06567873, first posted August 23, 2024. https://clinicaltrials.gov/api/v2/studies/NCT06567873