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Gastric ultrasound study identifies key metrics

June 18, 2024

A recent meta-analysis underscores the importance of gastric ultrasound in anesthetic practice, particularly for assessing the risk of pulmonary aspiration due to gastric contents. This study aims to establish a reliable upper limit for normal gastric antral area and volume in fasting adults, providing crucial benchmarks for safer anesthesia management.

The study analyzed data from 12 primary studies conducted between January 2009 and December 2020, encompassing 1,203 subjects. It determined that the 95th percentile for antral cross-sectional area (CSA) is 9.9 cm², and for gastric volume, it is 2.3 mL/kg. These values provide a critical benchmark for identifying patients at risk of aspiration.

Distribution of values of the cross-sectional area measured in the right lateral decubitus position (left) and the gastric volume (right) for all patients. The blue line indicates the median and the red line indicates the 95th percentile value based on the Harrell-Davis method and bootstrap method, respectively. CSA, cross-sectional area.

Historically, the threshold for high aspiration risk was set at a gastric volume of 0.8 mL/kg, based on animal studies. However, this meta-analysis reveals that this threshold is overly conservative. The findings suggest that the median gastric volume in fasting adults is approximately 0.6 mL/kg, with the 95th percentile reaching 2.3 mL/kg.

The study’s results are significant for clinical practice. They suggest that a gastric antral area of 10 cm² in the right lateral decubitus position can serve as a practical upper limit for fasting patients. Furthermore, the data indicate that an antral grade of 0 or 1 (indicating an empty or nearly empty stomach) correlates with a 98% probability of having a gastric volume below the 95th percentile, thus significantly reducing aspiration risk.

This research underscores the utility of gastric ultrasound as a non-invasive tool for evaluating gastric content at the bedside, especially when a patient’s fasting status is uncertain. It also emphasizes the importance of using updated and evidence-based metrics to improve patient safety in anesthetic practices.

To read the full paper in Anesthesiology, copy-paste this into your Google search:
Perlas A, Arzola C, Portela N, Mitsakakis N, Hayawi L, Van de Putte P. Gastric Volume and Antral Area in the Fasting State: A Meta-analysis of Individual Patient Data. Anesthesiology. 2024;140(5):991-1001.

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