Comparison of ultrasound measured gastric volume in term-pregnant patients posted for elective cesarean section with nonpregnant elective surgery patients---An observational study

Background: The pregnant patients undergoing anesthesia are at increased risk of aspiration due to decreased lower esophageal sphincter tone and mass effect of gravid uterus on gastric antrum. Ultrasound used as a noninvasive bedside imaging tool to measure gastric volume in term pregnant patients immediately before elective caesarian section (CS) may help in reducing aspiration induced morbidity and mortality. Methods: This observational prospective case--control study was conducted in 33 nonlaboring term pregnant patients immediately before elective CS and 30 nonpregnant patients immediately before elective surgeries, enrolled according to inclusion and exclusion criteria. A 2-5 MHz curvilinear probe was used to scan the participants in supine and right lateral decubitus (RLD) position in pre-recovery room. Visibility, qualitative grading (0,1, 2), anteroposterior (AP), and craniocaudal (CC) diameter, and cross-sectional area (CSA) of gastric antrum was measured. Gastric volume was derived from CSA using equations formulated by previous investigators. Results: Gastric antrum was visible in 27 (82%) of pregnant and 30 (100%) of nonpregnant patients in supine position (P = 0.014). In RLD position, 25 (75.7%) pregnant and 29 (96.7%) nonpregnant patients had antrum visible (P = 0.018). The qualitative grading was comparable (P = 0.064) in both the groups. In supine position, (P = 0.615), CSA in cm2 was 3.37 ± 1.31 and 3.54 ± 1.33, while in RLD position (P = 0.012), CSA was 3.98 ± 1.13 and 5.09 ± 1.85, in pregnant and nonpregnant patients, respectively. Conclusion: Gravid uterus sometimes impedes visualization of antrum by ultrasound in term pregnant patients immediately before elective CS and shows clinically similar gastric CSA when compared to nonpregnant patients, though statistically different in RLD position. Trial registration number- NCT03380637