Intra- and Interrater Reliability of Ultrasound Assessment of Gastric Volume

Background: Gastric sonography can provide information about gastric content and volume that can help determine aspiration risk at the bedside. The primary objective of this study is to assess the intrarater and interrater reliability of a previously validated method of gastric volume assessment based on gastric antral area. The secondary objective is to evaluate the agreement between two different methods to measure gastric antral area. Methods: Three independent raters performed a standardized gastric ultrasound assessment in healthy subjects who had been randomly allocated to ingest a predetermined volume of clear fluid (apple juice) from 0 to 400 ml. Each rater measured the gastric antral area, using twice the two-diameter method and twice the free-tracing method. The rater order was allocated at random and raters were unaware of the volume ingested and of one-another's measurements. The Guidelines for Reporting Reliability and Agreement Studies were followed for conducting and reporting this study. Results: Twenty-two volunteers were studied. Ultrasound assessment of antral cross-sectional area and volume was found to have nearly perfect intrarater and interrater reliability (correlation coefficient >0.8) with maximum differences within 13%. A Bland-Altman analysis suggests that the free-tracing method and the two-diameter method are essentially equivalent, within a clinically acceptable level of agreement. Conclusions: Ultrasound assessment of gastric volume by clinical anesthesiologists is highly reproducible with high intrarater and interrater reliability. The free-tracing method to measure antral cross-sectional area is equivalent to the two-diameter method.