Patients who have failed to disclose the use of weight loss jabs or illegal peptides before surgery could face "serious" consequences according to doctors, after a new study showed there was an 11-fold risk of regurgitation or aspiration for GLP-1 users.
Pulmonary aspiration, where material like food enters the airways and lungs, can be fatal and experts have described the increased risk for GLP-1 users under general anaesthetic as an "accident waiting to happen".
The Australian and New Zealand College of Anaesthetists (ANZCA) issued a fresh warning to patients, saying some were still failing to declare they were on the medication because they had forgotten, were embarrassed or were trying to conceal the purchase of unapproved peptides.
"They do worry that by disclosing these private personal details that they might be judged or they might be treated differently."
The use of GLP-1-based medications such as Ozempic or Mounjaro has been rising rapidly in Australia, with an estimated half a million people using them.
Authorities have also reported people self-injecting unapproved drugs like retatrutide, which is also a GLP-1-based medication.
GLP-1 drugs mimic the activity of a natural hormone, helping people feel full for longer.
But because they slow digestion, standard fasting might not empty a patient's stomach ahead of surgery, posing an increased risk of pulmonary aspiration.
"When you're under anaesthetic, your body's automatic safety reflexes like coughing and swallowing are switched off so food or fluid in there can come back up and then slip into the airway and lungs, and that can cause serious lung injury," Dr Selak said.
"It's quite rare, but it's the reason why we routinely ask patients to fast before surgery."
Doctors have been delaying surgery because of that risk, or using alternative methods to administer anaesthetics.
A new study published in the peer-reviewed Anaesthesia journal last month found patients on GLP-1s were 11 times more likely to regurgitate or aspirate contents under general anaesthetic than those not taking the medications.
The study looked at more than 47,000 patients across the UK and identified almost 1,350 people who had been taking GLP-1 drugs for three months prior to surgery.
Most of the cases only involved regurgitation, and generally patients regurgitated or aspirated as they woke up from anaesthesia, but the authors noted the link was not necessarily causal, as people with obesity or diabetes were already at increased risk of aspiration or regurgitation.
Stopping GLP-1s before surgery 'demonstrably stupid'
The research found around a third of patients were advised to stop taking their medication for a week before surgery.
But Professor Michael Horowitz, who specialises in gastrointestinal function at Adelaide University, said that advice was "demonstrably stupid" as slowed gastric emptying can persist for some time.
Pausing a GLP-1 can also be dangerous for people taking it to manage type 2 diabetes and there could be other possible implications, such as losing associated kidney benefits.
Professor Horowitz said given how "devastating" aspiration can be there must be more research to determine how long it takes for normal gastric emptying to return after stopping a GLP-1 drug.
"People are getting mixed advice because we don't have a good evidence base to give advice," he said.
ANZCA guidelines recommend patients on GLP-1 drugs take clear fluids for 24 hours, followed by a standard six-hour fast before surgery.
They also recommend anaesthetists specifically ask their patients whether they are on GLP-1 medication.
"Some people will come and write that they're not on any medications but by the time I've asked them a number of different things, we've found out … 'oh I'm on a peptide injection someone gave me at the gym'," Dr Selak said.
For Dr Selak, the message to patients is to be honest with their doctor about what medication they are taking.
"There is no judgement, we are partners in your care and that simple conversation can help us make the safest plan."
