Gastric ultrasonography in the fasted term pregnant women scheduled for elective Cesarean delivery: a prospective descriptive study

Abstract Number: T-30
Abstract Type: Original Research

Introduction: Pulmonary aspiration of gastric content is one of the most feared complications in obstetric anesthesia. Bedside gastric ultrasonography (US) can be reliably performed by anesthesiologists [1] to assess gastric content in the perioperative period,[2] and may be useful in risk assessment and clinical management. We aimed to describe the qualitative and quantitative US assessment of the gastric antrum in fasted pregnant women.

Methods: Prospective, descriptive study in non-laboring pregnant women at term scheduled for elective cesarean delivery. Subjects were examined after a minimum period of overnight fasting (solid food-8 hrs; clear fluids-2 hrs) and prior to the cesarean delivery. Two anesthesiologists performed a standardized scanning protocol of the gastric antrum: subjects on a 45-degree semi-recumbent position, first supine and then in the right lateral decubitus (RLD), using a 2-5 MHz curvilinear array transducer in a sagittal to right parasagittal plane on the epigastric area. Based on the qualitative assessment of the antrum, subjects were classified following a 3-point grading system [2]: grade 0, the antrum appears empty; grade 1, small fluid volume only seen in RLD suggesting residual gastric secretions; and grade 2: larger fluid volume seen both in supine and RLD. In addition, quantitative assessment was performed using 3 still images of the antrum at rest (between peristaltic contractions) in RLD to measure the cross-sectional area (CSA) with aid of the built-in caliper.

Results: We have recruited 40 of the 110 planed subjects. Age, height, weight, BMI, and gestational age: mean (SD) of 35.6(5) years, 163.1(8.2) cm, 79.1(15.3) kg, and 29.6(4.7) kg/m2, 38.6(0.9) weeks. Fasting period for solid food and clear fluids: median (IQR) of 13(3) and 3.75(6.5) hours. Qualitative assessment: grade 0 (18/40,45%), grade 1 (22/40, 55%), and grade 2 (0%). Quantitative assessment, mean (SD) [min-max] of CSA in RLD: 4.71 (2.1) [1.8-9.7] cm2. The qualitative grading system showed significant differences for the CSA in RLD: grade 0= 3.11 (0.8) cm2; and grade 1=6.09 (1.8) cm2; p-value<0.0001. There was no correlation between hours of fasting and CSA or qualitative grade.

Discussion: All women in our study presented with antral CSA compatible with residual gastric fluid.[3] Furthermore, applying the predictive model obtained in non-pregnant population,[4] our subjects presented with gastric volumes no greater than 110 ml. The qualitative 3-point grading system may be used to assess individual risk of perioperative gastric content aspiration. The quantitative measurement of antral CSA is a promising tool for predicting gastric fluid volume.

References

[1] Can J Anesth 2013; 60: 771–779

[2] Anesth Analg 2011; 113: 93–97

[3] Br J Anaesth 2014, Jan 8.

[4] Anesth Analg 2013; 116: 357–363.

SOAP 2014