Background: Ultrasound measurement of the antral cross-sectional area of the stomach, performed in the supine position, has been described for preoperative assessment of gastric content in the adult, but, to date, no study has determined the cut-off value of the antral area for the diagnosis of an empty stomach in the parturient. Nevertheless, previous studies in parturients have reported that the use of a simple qualitative grading scale (0 to 2) was reliable for the estimation of the gastric fluid volume. However, this qualitative grading score requires turning the parturient into the right lateral decubitus position for the ultrasound examination, something which may not be easily feasible, particularly in the case of an obstetric emergency.
Objective: To calculate the cut-off value of the antral area, measured in the supine position during established labour, for the diagnosis of 'empty' stomach.
Design: A prospective cohort study.
Setting: Hospices Civils de Lyon, Hôpital Femme Mère Enfant, Lyon, France.
Patients: Seventy-three women in established labour.
Interventions: For each parturient, ultrasound assessment of gastric contents was performed in the supine and right lateral decubitus position and scored 0 to 3 on a qualitative grading scale. This assessment was followed by ultrasound measurement of the antral cross-sectional area in both the supine and right lateral positions.
Main outcome measures: To assess the performance of the antral area measured in the supine position for the diagnosis of an 'empty' stomach (gastric antrum grade 0), a receiver operating characteristic curve was plotted, and the area under the receiver operating characteristic curve was calculated.
Results: Data from 73 women were analysed. For the diagnosis of grade 0, the cut-off value for the antral area measured in the supine position was 381 mm (sensitivity, 81%; specificity, 76% and negative predictive value, 80%).
Conclusion: With a parturient lying in the supine position, a single assessment of the antral cross-sectional area may be used for the fast diagnosis of an empty stomach. This tool could be useful in assessing the risk of aspiration for parturients who require emergency anaesthesia during labour.