Background: Healthy nonpregnant and pregnant patients may ingest clear liquids until 2 h before induction of anesthesia without adversely affecting gastric volume. In this study, we compared gastric emptying in obese, term, nonlaboring pregnant women (prepregnancy body mass index >35 kg/m2) after the ingestion of 50 and 300 mL of water.
Methods: Gastric emptying was assessed in 10 obese, term pregnant volunteers using both serial gastric ultrasound examinations and acetaminophen absorption in a crossover study design. After an overnight fast, volunteers ingested 1.5 g acetaminophen and 50 or 300 mL water (randomly assigned) on two occasions separated by at least 2 days. Serial gastric antrum cross-sectional areas were determined using gastric ultrasound imaging and the half-time to gastric emptying (T([1/2])) was calculated. Areas under the plasma acetaminophen concentration versus time curve (AUC), peak concentrations (C(max)), and time to peak concentration (t(max)) for 50 mL and 300 mL ingestions were compared.
Results: Mean prepregnancy body mass index was 41 +/- 9 kg/m(2). Gastric emptying T([1/2]) was not different after ingestion of 300 mL water compared with 50 mL (23 +/- 11 min vs 32 +/- 15 min). There were no differences between acetaminophen AUCs at 60, 90, or 120 min, C(max) or t(max) after ingestion of 300 mL compared with 50 mL of water.
Conclusions: Gastric emptying in obese, nonlaboring term pregnant women is not delayed after ingestion of 300 mL compared with 50 mL of water. Gastric antral volume after ingestion of 300 mL of water is similar to the baseline fasting level at 60 min.