Assessment of the Diagnostic Performance of Qualitative Ultrasound Assessment of Gastric Contents for the Detection of Gastric Fluid Volume ≥ 1.25 ml/kg in Children

Pulmonary aspiration of gastric contents is a complication responsible for the third highest cause of anaesthesia-related mortality in France, and for 50% of airway management-related mortality in the UK. The occurrence of pulmonary aspiration of gastric contents is often the result of a poor assessment of the risk of a "full" stomach, and could therefore often be avoided if the preoperative gastric contents were known to the anaesthetist. It is therefore useful to be able to discriminate easily between patients at risk of aspiration and those at low risk before general anaesthesia, and this can be done by ultrasound examination of the gastric contents in the gastric antrum, non-invasively (abdominal ultrasound) using a 2-5 MHz abdominal ultrasound probe or a high-frequency linear probe in small children (under 10 kg). European recommendations on preoperative fasting in paediatrics recommend that the examination should be interpreted in a qualitative manner only, without measuring the antral surface. However, the diagnostic performance of this qualitative approach alone has never been evaluated. The aim of this study was to determine the diagnostic performance of the qualitative assessment of gastric contents by ultrasound in children, and to compare it with that of the clinical algorithm, for the detection of a volume of fluid greater than 1.25 ml/kg.

Children will present themselves in the morning after fasting. Upon arrival, if their weight is not known, the children will be weighed. Subsequently, they will be positioned on an examination table in a supine inclined position at 45° (head of the bed elevated). An initial gastric ultrasound will be performed by a physician (investigator 1) who will not conduct the study ultrasounds. This initial ultrasound aims to confirm the absence of gastric content in the supine and right lateral decubitus positions, thereby establishing gastric emptiness.

Investigator 1 will then proceed with the random selection of the clear liquid volume to be ingested for the study.

The child will then be asked to drink this determined volume of clear liquid (water or apple juice according to their preference), as per the randomization results, under the supervision of the first investigator who performed the initial ultrasound.

Subsequently, investigator 2 will perform a gastric ultrasound blindly with respect to the ingested liquid volume, three minutes after the consumption of the clear liquid. The examination will last a maximum of 3 minutes.

Non-invasive gastric antrum ultrasound examinations will utilize a probe with a frequency of 2-5.5 MHz and a linear probe with a frequency of 10 MHz, enabling the evaluation of the gastric antrum's appearance. The diameters (longitudinal D1 and anteroposterior D2) of the antrum will also be measured in the supine (semi-seated and lying) and right lateral positions in the sagittal plane passing through the abdominal aorta and the left lobe of the liver, for the calculation of the antral section area, given by the formula: Antral area = π x D1 x D2 / 4.