Standard pre-surgery fasting may not be enough for patients taking GLP-1s and other weight-loss peptides, Australian anaesthetists have warned.
Patients taking GLP-1 receptor agonists had 11 times the odds of regurgitation or pulmonary aspiration during anaesthesia, according to a major prospective study that has prompted a fresh warning from Australian anaesthetists.
The Australian and New Zealand College of Anaesthetists has urged patients using GLP-1 drugs or other weight-loss peptides to disclose them before surgery, warning that delayed stomach emptying can leave food in the stomach even after standard fasting.
ANZCA president Dr Tanya Selak said the consequences could be life-threatening if stomach contents entered the lungs during surgery.
“These medications can slow the emptying of the stomach which may still contain food or other material even when you have followed the usual fasting instructions,” she said.
“We know of some rare cases where the consequences of stomach contents entering the lungs during surgery (pulmonary aspiration) can be extremely serious and life-threatening for patients.”
The large prospective UK study published in Anaesthesia, screened 47,039 patients across 119 hospitals. Of those, 1348, or 2.9%, had used a GLP-1 receptor agonist in the three months before their procedure.
Regurgitation or pulmonary aspiration occurred in 1.41% of patients taking GLP-1 drugs, compared with 0.12% of patients who were not. That translated to an odds ratio of 11.39 (95% CI 6.47-20.05).
But the absolute risk of pulmonary aspiration alone was considerably lower. Just two of the 1348 GLP-1 users experienced pulmonary aspiration, an event rate of about one in 674.
Most of the 19 events in GLP-1 users involved regurgitation without pulmonary aspiration.
The researchers cautioned that the observational study could not establish that GLP-1 drugs caused the increased risk. Obesity and diabetes, themselves risk factors for aspiration, were over-represented among GLP-1 users and could have confounded the results.
More than half of the aspiration or regurgitation events among GLP-1 users occurred during emergence from anaesthesia, rather than induction, prompting the researchers to flag safe extubation as an important consideration.
Tirzepatide accounted for 70% (942 patients) of GLP-1 use in the study and semaglutide for another 26% (353). Weight loss was the indication in 59% of patients (794), while 23% (315) were using the drugs for diabetes and 13% (176) for both conditions .
The study also exposed substantial variation in perioperative management. Thirty per cent of GLP-1 users had been asked to stop their medication before surgery, most commonly for eight to 14 days.
The researchers noted that it remained unclear how long the drugs would need to be withheld to reduce residual gastric contents.
“In conclusion, this prospective observational study reported that 1 in 36 patients undergoing anaesthesia care receive GLP-1 RAs and their peri-operative management is variable,” they wrote.
“A range of airway management techniques consistent with reducing aspiration risk were observed, and despite this, the incidence of pulmonary aspiration and/or regurgitation was 1 in 71 in patients receiving GLP-1 RAs; this occurred most commonly during emergence from anaesthesia.
“These data warrant further prospective studies to determine interventions that may mitigate risks of pulmonary aspiration and improve patient outcomes.”
ANZCA has recently updated its fasting information to generally allow patients small amounts of clear liquids until they are called to theatre, while solid food and non-clear liquids should cease six hours before elective surgery.
Patients taking GLP-1 drugs or other weight-loss peptides may need different instructions because of delayed gastric emptying, including potentially switching to fluids only from the day before their procedure.
ANZCA’s patient information now generally allows small amounts of clear liquids until patients are called to theatre, while solid food and non-clear fluids should stop six hours before elective surgery.
Dr Selak said any changes to GLP-1 treatment must be done in collaboration with the patient’s medical team, including anaesthetists.
“The important message for patients is not to stop your medication on your own,” she said.
“Instead, make sure your surgical and anaesthesia team knows that you are taking it so they can provide individual advice about fasting and your anaesthetic.”
Patients should tell their anaesthetist exactly what they are taking, when they last took it and why, she said.
The warning also extends to weight-loss peptides obtained outside conventional prescribing channels. It follows recent TGA compliance action targeting suppliers and manufacturers of unapproved performance and image-enhancing products sold online.
Dr Selak said patients should not assume weight-loss injections or peptides were irrelevant to their anaesthetic care.
“Your anaesthetist needs to know if you are taking these medications so they can assess the safest approach for your procedure,” she said.
