Could the fluid be gastric content?

Determining if Fluid is Gastric Content

Yes, the fluid could be gastric content, and this should be assessed using point-of-care gastric ultrasound to visualize the type and volume of gastric contents, particularly in high-risk patients such as those on GLP-1 receptor agonists, those with delayed gastric emptying, or those who have not met appropriate fasting intervals. 1

Clinical Assessment Approach

Primary Risk Factors for Retained Gastric Contents

Patients on GLP-1 receptor agonists represent the highest risk group:

• 56% of patients on GLP-1 receptor agonists had retained gastric contents despite complying with standard fasting guidelines, compared to only 19% in control groups 1
• Long-acting GLP-1 receptor agonists (semaglutide, dulaglutide, liraglutide) showed significantly higher incidence of gastric residue (5.4% vs. 0.5% in controls) even after prolonged fasting of at least 12 hours 1
• Seven out of 10 patients taking semaglutide had solids in the stomach despite a 10-hour fast 1

Other high-risk scenarios include:

• Patients with recent medication initiation or dose increases of GLP-1 receptor agonists 1
• Those experiencing nausea, vomiting, or abdominal distention 1
• Patients with gastroparesis, diabetes with hyperglycemia, or gastro-oesophageal surgery history 1
• Critically ill patients with MDR bacteria growth or negative fluid balance (63% incidence of GI dysfunction) 2

Diagnostic Strategy Using Gastric Ultrasound

Point-of-care gastric ultrasound is the recommended method to definitively determine if fluid is gastric content: 1, 3

Ultrasound Assessment Protocol

• Measure antral cross-sectional area (CSA) in the lateral decubitus position 1
• Calculate gastric fluid volume using the validated formula: Volume (ml) = 27.0 + 14.6 × CSA - 1.28 × age 1
• Critical threshold: Gastric volume >1.5 ml/kg indicates increased aspiration risk 1, 4
• Distinguish between empty stomach, clear fluids, and solid matter 3

Interpretation of Findings

• Presence of any solid matter = high-risk "full stomach" regardless of volume 1
• Clear fluid >1.5 ml/kg = increased aspiration risk 1
• Thick liquids or solids = definite retained gastric contents requiring intervention 1

Management Based on Gastric Content Assessment

If Retained Gastric Contents Identified

For elective procedures:

• Postpone and reschedule the procedure 1
• Hold GLP-1 receptor agonists for at least three half-lives (approximately 1 week for weekly agents, day of procedure for daily agents) 1, 4
• Consider clear fluid diet for extended period before pre-operative fasting 1

For urgent/emergent procedures:

• Administer prokinetic drugs (metoclopramide or erythromycin) pre-operatively 1
• In very high-risk patients, consider pre-emptive gastric decompression with nasogastric tube 1
• Use rapid-sequence intubation to reduce aspiration risk 1

Special Considerations for Enteral Feeding Patients

In ICU patients receiving tube feeding:

• Gastric residual volumes (GRV) should be monitored in patients with feeding intolerance or high aspiration risk 1, 5
• Continue enteral feeding unless GRV exceeds 500 mL per 6 hours 5
• Position patients at 30° or more during feeding and for 30 minutes after 5
• If GRV >200 ml, review feeding policy; if >500 ml, temporarily hold feeding and consider prokinetics 5

Common Pitfalls to Avoid

Do not rely solely on fasting times: Even 2-hour fasting for clear fluids does not guarantee an empty stomach, with considerable inter-individual variation 1

Do not assume standard fasting is adequate for GLP-1 receptor agonist users: There is no association between duration of drug discontinuation and prevalence of retained gastric contents in standard timeframes 1

Do not ignore recent medication changes: Patients who recently started GLP-1 receptor agonists or increased doses are at particularly high risk 1

Do not forget to assess for gastroparesis in diabetic patients: Acute hyperglycemia without diagnosed gastroparesis can predispose to acute gastric dilatation 6