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Ultrasonographic measurement of antral area for estimating gastric fluid volume in parturients.

BACKGROUND
The aim of this prospective observational study was to assess the performance of ultrasonographic gastric antral area (GAA) to predict gastric fluid volumes of >0.4, >0.8 and >1.5 ml kg(-1), in fasted women in established labour.


METHODS
A first ultrasound examination of the antrum was performed, in order to confirm gastric vacuity by using a qualitative score. Baselines GAA measurements were obtained in both supine and right lateral decubitus positions. Thereafter, parturients were allowed to drink clear fluids only. Measurement of GAA was repeated 15 min after last fluid intake, in both supine and right lateral positions. Receiver operating characteristics (ROC) curves were constructed to determine the accuracy of GAA to diagnose ingested volumes of >0.4, >0.8 and >1.5 ml kg(-1).


RESULTS
Data from forty parturients were analysed. The areas under the ROC curves ranged from 80% to 86%. The cut-off value for antral area measured in supine position, to detect a volume >0.4 ml kg(-1), was 387 mm(2), with a sensitivity of 87%, a specificity of 70% and a negative predictive value of 85%. A cut-off value of 608 mm(2) predicted a fluid volume >1.5 ml kg(-1), with a specificity of 94%, a sensitivity of 75% and a negative predictive value of 92%.


CONCLUSIONS
This study provides cut-off values for GAA that could be used in addition to the qualitative assessment of the antrum to define a full stomach in labouring patients.