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Bedside Ultrasound Assessment of Gastric Volume in Pregnant Women at Term: Development of a Predictive Model
Abstract Number: T-41
Abstract Type: Original Research
Introduction: Pulmonary aspiration of gastric content is one of the most feared complications in obstetric anesthesia. Bedside gastric ultrasonography (US) is a feasible imaging tool that can be reliably performed by anesthesiologists to assess gastric content in the perioperative period.1,2 We studied the relationship between the gastric antral area assessed by US and the volume of clear fluids ingested aiming to develop a predictive model to estimate gastric volume.
Methods: We conducted this randomized single-blinded study in non-laboring pregnant women at term. A standardized scanning protocol of the gastric antrum was carried out using a 2-5 MHz curvilinear array transducer in a sagittal to right parasagittal plane on the epigastric area by one of two anesthesiologists. Subjects were on a 45-degree semi-recumbent position. Firstly, we performed a baseline qualitative assessment of the gastric content after an 8-hour fasting period in supine and in right lateral decubitus (RLD). Women were classified following a 3-point grading system (grade 0: no fluid; grade 1: fluid seen in RLD only; grade 2: fluid seen in both positions). Secondly, subjects were randomized to ingest one of 6 predetermined volumes of apple juice (0-50-100-200-300-400 ml). A quantitative assessment was performed through a series of sonographic measurements of the cross-sectional area of the antrum (CSA) at baseline and after the volume ingestion. The anesthesiologist performing the US examinations was blinded to the volume allocation. Primary outcome: the relationship between antrum CSA and volume ingested were analyzed through Pearson correlation coefficients. Secondary outcome: multiple regression analysis was used to create a mathematical model to estimate gastric volume.
Results: We have examined 56 out of 60 subjects. Preliminary results show that the CSA in RLD correlated well with volumes ingested (Pearson’s correlation r=0.65). Various mathematical models were tested statistically significant, which incorporate CSA in RLD and demographics such as age, gestational age, height and BMI (Coefficient of determination R2=0.42 to 0.7)
Discussion: Bedside gastric US is a feasible tool in the assessment of pregnant women. The antrum CSA correlates well with the volume ingested. We developed a predictive model to estimate gastric volumes based on antral CSA and patient demographics. The quantitative measurement of antral CSA is a promising tool. Further research is warranted to identify the best use of this point-of-care diagnostic modality.
1. Can J Anesth 2013;60:771–9.
2. Anesth Analg 2011;113:93–7