Effect of metoclopramide on gastric volume and nausea and vomiting in fasted patients undergoing elective cesarean delivery: a randomized clinical equivalence trial

Background: The American Society of Anesthesiologists Practice Guidelines for Obstetric Anesthesia recommend preoperative fasting and aspiration prophylaxis including non-particulate antacids, H₂-receptor antagonists, and/or metoclopramide for elective cesarean deliveries. This study evaluated the effect of metoclopramide on gastric volume in appropriately fasted patients undergoing elective cesarean delivery. Methods: We conducted a single-center, randomized, placebo-controlled equivalence trial of appropriately fasted patients presenting for elective cesarean delivery. Patients were randomized to receive intravenous metoclopramide 10 mg or saline. Gastric ultrasound was performed before and 30 minutes after study medication administration in the right lateral decubitus and the supine positions. Gastric volumes were estimated using the Roukhomovsky and Perlas methods. We hypothesized that metoclopramide would not significantly decrease gastric volume compared to saline within the equivalence limits of ± 17 mL. Results: Seventy-two patients completed the study. Median gastric volume estimates were greater using the Roukhomovsky compared to the Perlas method (pre-treatment difference 13 mL, P < 0.001; post-treatment difference 11 mL, P < 0.001). No differences in the number of patients identified as at risk for aspiration (gastric volume > 1.5 mL/kg) were found between groups. The median pre- to post-treatment difference in gastric volume between saline and metoclopramide groups, calculated using the Perlas method, was −1 mL (95 % CI −5 to 2, P = 0.375) and 1 mL (95 % CI −4 to 5, P = 0.981) using the Roukhomovsky method. Equivalence was determined significant for both methods (P < 0.001). Discussion: In appropriately fasted patients, metoclopramide and saline were equivalent in their effect on gastric volume within ± 17 mL, showing metoclopramide administration had minimal effect on gastric volume in this low-risk population.