1. INTERPRETATION OF FINDINGS
- Defining the type of content (empty, clear fluid or thick fluid/solid) is the first step. An empty stomach is suggestive of low aspiration risk. Solid content is suggestive of a high aspiration risk.
- The risk implications of an empty stomach (low risk) and solid content (high risk) as self-evident.
- When clear fluid is present, a volume assessment can discriminate between a low volume compatible with a fasting state (Grade 1 antrum and ≤1.5 mL/Kg), vs. a high volume suggestive of a non-fasting state (Grade 2 antrum and >1.5 mL/Kg).
2. Medical Decision Making
Your findings will help you decide if you should:
- Proceed ± aspiration profylaxis
- Insert nasogastric tube: pre-, per- or post-operatively
- Use a laryngeal mask or endotracheal tube
- Do standard intubation or rapid sequence
Ultrasound findings can help decide if it is safe to proceed with elective surgery when there is questionable fasting status.
In case of urgent or emergency surgery that needs to proceed, gastric ultrasound findings can help decide:
if you are dealing with an empty or full stomach
what type of airway management is required e.g. tracheal intubation versus supraglottic airway
if a standard induction/intubation or a rapid sequence intubation is rerquired
to decide if the stomach is amenable for suctioning with a nasogastric tube in the context of a full stomach (‘fluid versus solid’)
3. LIMITATIONS OF GASTRIC ULTRASOUND
Gastric ultrasound findings may be inaccurate in subjects with abnormal underlying gastric anatomy. For example:
- Previous gastric resection or bypass
- Gastric band in situ
- Previous fundoplication
- Large hiatus hernia
Empty stomach (any of the following)
- No content visible in any patient position (Grade 0 antrum)
- Clear fluid in the right lateral decubitus but appears empty when supine (Grade 1 antrum)
- Clear fluid with a cross-sectional area of < 10 cm2 in the RLD for an average adult
- Clear fluid with estimated Gastric volume < 1.5 mL/Kg
Full stomach (any of the following)
- Thick fluid or solid content in any patient position
- Antrum distended with clear fluid evident in both supine and right lateral decubitus (Grade 2 antrum)
- Clear fluid with cross-sectional area > 10 cm2 in the RLD for an average adult
- Clear fluid with estimated Gastric volume ≥ 1.5 mL/Kg
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