Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1-RA) such as semaglutide (Ozempic™, Rybelsus™, Wegovy™) were first introduced as a therapeutic agent for type 2 diabetes mellitus but they are being increasingly used to target weight loss in obesity.

One of the mechanisms by which weight loss is achieved, is increased satiety and significantly delayed gastric emptying. Tachyphylaxis for this effect has been reported with chronic use of long acting GLP-1-RA (e.g. semaglutide) but this was based on the paracetamol absorption technique or 13C breath test. Recent clinical data suggests semaglutide use does increase perioperative gastric content.This creates uncertainty for anaesthetists who are, anecdotally, more frequently faced with patients who may or may not have full stomachs despite adhering to conventional fasting guidelines.

To address this issue the American Society of Anesthesiologists (ASA) has recently released guidelines in which it advises to hold GLP-1-RA for one day (if administered daily) or one week (if administered weekly).

However, these recommendations are based on sparse empirical evidence and they do not necessarily follow from the known pharmacokinetic properties of these drugs. Typically, GLP-1-RA are administered in increasing doses over several weeks until a therapeutic steady state is achieved. Meanwhile the elimination half-life of e.g. semaglutide is 7 days. This means that holding semaglutide for one day or even one week might not be enough to attenuate its therapeutic effect of delayed gastric emptying. On the other hand if semaglutide were to be held for e.g. 5 terminal half-lifes, this would mean an unpractical 5 weeks during which glycemic control may be worsened and after which semaglutide doses would have to be incrementally increased again. Besides, hyperglycaemia secondary to semaglutide cessation can also delay gastric emptying.

Further confounding the assessment of these patients there can be 'background' delayed gastric emptying in diabetic patients and more pronounced delayed gastric emptying in patients recently started on GLP-1-RA. The presence of gastro-intestinal symptoms (nausea, vomiting, dyspepsia, abdominal distension) might offer clinical information regarding increased gastric residue in this population.

Gastric ultrasound is a point-of-care clinical and research tool that has steadily gained popularity to assess gastric content in patients not compliant with fasting rules or with certain comorbidities. Clinical decisions can be made based on the visualised content (e.g. solids, fluids or nothing) or through calculation of gastric volume by measuring antral circumference. In this study the investigators will examine gastric contents in patients who are taking semaglutide and in patients who are not. The investigators will then evaluate whether there is a difference in the incidence of full stomachs and whether gastric ultrasound influenced the anaesthetic plan of the treating anaesthetist.

Inclusion criteria for the semaglutide cohort are:

• Adults (>=18 years old)
• Semaglutide therapy for any indication (type 2 diabetes or weight loss)
• Semaglutide therapy at any dose
• Semaglutide therapy with any route of administration
• Semaglutide therapy administered daily or weekly
• Semaglutide therapy at any time since initiation
• Elective surgery of any kind for which general anaesthesia was planned preoperatively
• Adherence to current ASA recommendation regarding GLP-1-RA; i.e. holding semaglutide for 1 week if administered weekly or for 1 day if administered daily.
• Adherence to current ESAIC fasting guidelines; i.e. >2 hours for liquids and >6 hours for solid foods.

Inclusion criteria for the control cohort are:

• Adults (>=18 years old)
• Elective surgery of any kind for which general anaesthesia was planned preoperatively
• Adherence to current ESAIC fasting guidelines; i.e. >2 hours for liquids and >6 hours for solid foods

Exclusion criteria for the semaglutide cohort are:

• Semaglutide not held in accordance with current ASA recommendation, i.e. held either longer or shorter than recommended.
• No adherence to current ESAIC fasting guideline
• Presence of a contra-indication to gastric ultrasound; i.e. previous gastric surgery (e.g. partial gastrectomy, gastric bypass) or hiatal hernias.
• Presence of comorbidities associated with delayed gastric emptying: scleroderma, systemic lupus erythematosus, hypothyroidism, Parkinson disease, cerebral palsy, and multiple sclerosis.
• Inability to assume the right lateral decubitus position
• Initial anaesthetic plan did not involve general anaesthesia, e.g. neuraxial or locoregional cases

Exclusion criteria for the control cohort are:

• Semaglutide or other GLP-1-RA therapy
• No adherence to current ESAIC fasting guideline
• Presence of a contra-indication to gastric ultrasound; i.e. previous gastric surgery (e.g. partial gastrectomy, gastric bypass) or hiatal hernias
• Presence of comorbidities associated with delayed gastric emptying: scleroderma, systemic lupus erythematosus, hypothyroidism, Parkinson disease, cerebral palsy, and multiple sclerosis
• Inability to assume the right lateral decubitus position
• Initial anaesthetic plan does not involve general anaesthesia, e.g. locoregional cases