The relationship between gastric ultrasound findings and endoscopically aspirated volume in infants and determining the antral cutoff value for empty stomach diagnosis
Pediatric Anesthesia
Submitted August 2024 by Dr Aisling Gormley
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This single centre, prospective observational study, performed in a paediatric endoscopy unit between November 2021 and June 2022 examines the relationship between ultrasound measured gastric antrum cross-sectional areas (CSAs), and volumes aspirated by endoscopic suction. It aims to determine a cutoff for antral CSA that correlates with empty stomach diagnosis and assess the utility of a three-point qualitative grading system for identifying the “at risk” stomach.
46 children <2 years, fasted to standard guidelines for age, ASA I or II, undergoing elective gastroscopy were recruited. All children were lightly sedated to tolerate examination whilst maintaining spontaneous ventilation.
A single experienced operator undertook ultrasound of the gastric antrum in supine and right lateral decubitus (RLD). Antral CSA, and gastric contents were assessed. Gastroscopy was then undertaken. All gastric content was aspirated under direct vision and recorded. The 3-point grading system stratified patients as Grade 0 for empty appearances in supine and RLD, Grade 1 for gastric content seen in RLD only, Grade 2 for gastric content seen in both supine and RLD.
• Significant correlation was found between aspirated gastric volume and RLD CSA (p 0.003), but not for supine CSA.
• Mean aspirate was 0.13± 0.22ml/kg, indicating all patients had aspirates below the volume considered at risk for paediatric patients (1.25ml/kg).
• Optimal CSA cutoff for an empty antrum was determined by Youden’s Index as <2.40cm2, measured in RLD (sens 100% spec 68.6%).
• The grading system classified patients as Grade 0- 76.1%, Grade 1- 23.9%, and Grade 2- 0%. Patients with a Grade 0 antrum had minimal or no gastric aspirate (median 0.0ml/kg; 0.0-0.09 IQR; sig p<0.001). Those with Grade 1 antrum had significantly higher CSA when measured in RLD compared with supine.
Discussion points:
This was a small study, but findings are in keeping in with similar work. RLD CSA measurement predictably correlates better than supine CSA for aspirated gastric volume. Findings suggest that measurement of supine CSA alone has limited diagnostic value. A CSA of 2.40cm2 measured in RLD is 100% sensitive for diagnosing an empty stomach, allowing the assessing anaesthetist to confidently treat as fasted. However, where CSA is greater a more detailed assessment including mathematical formulae is advocated.
The grading system provided additional information on gastric “fullness” and should be used in conjunction with RLD CSA measurement to assist in decision-making.
ASA III and above children were excluded. This limits extrapolation as these groups will be more likely to have conditions or take medications altering gastric motility. Further research is needed in this area and this group may benefit most from gastric ultrasound.
Take home Message:
This study demonstrates that gastric ultrasound can be used to safely identify fasted and “at risk” stomachs and avoid unnecessary cancellation or intubation.
Given that co-operation can be challenging, isolated measurement of antral CSA taken in RLD can be used to confirm fasted state, but additional measurements and grading can add to operator confidence. A note of caution- the operator in this study was highly experienced in imaging techniques, but those of us less experienced with gastric ultrasound may need to upskill prior to committing to anaesthesia based on our ultrasound findings alone.
