Are the Fasting Guidelines Flawed, Regardless of Diabetes Status?
Dr. Horowitz also faulted the ASA’s 2017 guidance revision for allowing clear liquids to be consumed up to 2 hours in advance of anesthesia because it doesn’t distinguish between liquids with and without calories.
“Whether you have diabetes or not, if you are allowed to have a sugar drink up to 2 hours before your operation, the majority of people empty at about 4 kcal/min, so they will still have some of that drink in their stomach,” he said. “If you want an empty stomach, the ASA guidelines are wrong.”
That explains why the study found relatively high rates of “full stomach” in both groups, 15.5% of those with diabetes and 11.5% of those without, he said.
The GLP-1 Agonist Factor
Although the study didn’t address GLP-1 receptor agonist use, Dr. Warner did in his accompanying editorial, noting that the drugs’ rapid expansion “will likely change how we use perioperative fasting guidelines. With these medications delaying gastric emptying times, we now have another risk factor for pulmonary aspiration to consider when applying fasting guidelines. The inconsistent impact of GLP-1 agonists on gastric emptying, ranging from little to significant, makes it difficult for anesthesiologists to gauge whether or not patients taking GLP-1 agonists are likely to have preoperative gastric liquid or solid contents that could cause subsequent damage if regurgitated.”
Gastric ultrasound can be helpful in this situation, Dr. Warner wrote. In addition, he endorsed the 2023 ASA guidance, which calls for withholding daily-dosed GLP-1 agonists on the day of the surgery and the weekly formulations for a week. And if gastrointestinal symptoms are present, delay elective procedures.
But Dr. Horowitz said those recommendations are likely insufficient as well, pointing to data suggesting that daily liraglutide can delay gastric emptying for up to 16 weeks in about a third of patients. Such studies haven’t been conducted by the manufacturers, particularly on the once-weekly formulations, and the ensuing risk for aspiration isn’t known.
“The slowing occurs in much lower doses than are used for glucose lowering,” Dr. Horowitz said. “It is very likely that plasma levels will need to be extremely low to avoid gastric slowing. The current guidelines fail to appreciate this. So, to withhold the short-acting drugs for 1 day is probably wrong. And to stop long-acting drugs for 1 week is almost certainly wrong too.”
But as for what should be done, he said, “I don’t actually know what you do about it. And no one does because there are no data available to answer the question.”
The study received funding from the Physicians’ Services Incorporated Foundation and the Canadian Society of Anesthesiologists. Dr. Perlas received support for nonclinical time through a merit award from the Department of Anesthesiology and Pain Medicine, University of Toronto, and the Department of Anesthesia and Pain Management, Toronto Western Hospital, University Health Network. She is an executive editor of the journal Regional Anesthesia and Pain Medicine and does consulting work for FujiFilm SonoSite. Dr. Horowitz had no relevant disclosures.
A version of this article appeared on Medscape.com.