The aim of this randomised controlled trial is to determine the effect of a 24-hour clear liquid diet compared to standard fasting guidelines on the proportion of participants who present with increased residual gastric contents during their study visit. It also aims to determine the effect of a 24-hour clear liquid diet compared to standard fasting guidelines on:

• Solid content or thick fluids
• Patient-reported outcome measures (PROMs), including thirst, hunger, nausea, fatigue, and anxiety.
• Compliance measures, including adherence with the intervention, time since last oral intake of solid foods, and time since last oral intake of clear liquids.

We will enrol adults who are currently using any once-weekly glucagon-like peptide-1 receptor agonist (GLP-1RA) medication. Participants will be allocated in a 1:1 ratio to follow a 24-hour clear liquid diet or standard fasting guidelines prior to attending a study visit where participants will undergo a blinded gastric ultrasound assessment.

GLP-1 RAs have had a transformative impact on the management of obesity, cardiovascular disease, and type 2 diabetes. Despite this, this class of medications pose a significant challenge in the perioperative setting, as GLP-1 RAs are known to increase patients' risk of presenting to surgery with residual gastric contents even when standard fasting guidance is adhered to. Such residual contents pose a risk for devastating complications if they are aspirated during surgery. In procedures such as upper endoscopy, where clear visualisation of the gastric tract is essential, the presence of residual contents in the stomach may result in procedures being aborted, leading to patients being exposed to additional risks associated with having to repeat the procedure. Despite the urgent need for clear guidance based on reliable evidence, healthcare professionals are currently practicing in an almost complete absence of evidence regarding the management of GLP-1 RAs in the perioperative period.

Our trial aims to address the uncertainty around pre-procedure management of patients using GLP-1 RAs by evaluating whether a 24-hour clear liquid diet can reduce the likelihood of increased residual gastric contents in patients using once-weekly GLP-1 RA medications, compared to the standard fasting guidelines currently recommended before elective procedures. Standard fasting guidelines, as defined by the ASA and ANZCA, recommend clear liquids up to 2 hours before anaesthesia, a light or low calorific meal up to 6 hours before anaesthesia, and fasting from fried foods, fatty foods, or meat for at least 8 hours prior to anaesthesia.The trial will also examine the effect of this more stringent fasting guidance on outcomes including thirst, hunger, nausea, fatigue, and anxiety, which impact both comfort and satisfaction among patients undergoing surgery.

Inclusion Criteria:

• Age ≥18 years old at enrolment.
• Have regularly administered any type of once-weekly GLP-1 RA medication for a period of at least one month prior to randomisation.
• If allocated to follow standard fasting guidelines, willing to adhere to ASA and ANZCA preoperative fasting requirements. This requires participants to only consume clear liquids up to 2 hours, a light or low calorific meal up to 6 hours, and fasting from fried foods, fatty foods, or meat for at least 8 hours prior to the trial visit.
• If allocated to follow a 24-hour clear liquid diet, willing to adhere to nothing-by-mouth (NPO) for solids and last intake of clear liquids no less than 2 hours prior to the trial visit.
• Provide a signed and dated informed consent form for study participation in line with the requirements of the human research ethics committee (HREC) of the study site.

Exclusion Criteria:

Participants meeting any of the following criteria, indicative of abnormal anatomy and not validated by gastric ultrasound, will be excluded from this trial:

• Has a recent history of gastrointestinal bleed within the previous 1 month from enrolment.
• Has a history of previous lower oesophageal or gastric surgery.
• Has a known abnormal upper gastrointestinal anatomy, including hiatus hernia or gastric tumours.

In addition, participants meeting any the of following criteria will be excluded from this trial:

• Participant reports having been previously diagnosed with a clinically significant gastric emptying abnormality such as gastroparesis.
• Participant reports concomitant use of insulin.
• Unable to assume the right lateral decubitus position required for gastric ultrasound assessment.
• Participant has difficulty fully understanding PICF or study materials due to a primary language other than English.

The following will be made available long-term for use, by request, from future researchers from a recognised research institution whose proposed use of the data has been ethically reviewed, approved by an independent committee, and can demonstrate a safe data management plan.

Upon request

By request, from future researchers from a recognised research institution whose proposed use of the data has been ethically reviewed, approved by an independent committee, and can demonstrate a safe data management plan.