A Low-Dose Oxytocin Protocol Decreases Quantitative Blood Loss in Elective Cesarean Sections: A Single-Center, Retrospective Cohort Study.

INTRODUCTION: The prophylactic use of oxytocin after cesarean delivery has been shown to reduce maternal blood loss by 40 to 50%, yet there remains significant clinical deviation in how the medication is dosed. In January, 2021, the Defense Health Agency issued Procedural Instruction 6025.35 entitled Guidance for Implementation of the Postpartum Hemorrhage Bundle. This directive established a set of processes and procedures for the risk assessment and treatment of postpartum hemorrhage, including a new standardized oxytocin protocol for vaginal and cesarean deliveries. The purpose of this study was to compare quantitative blood loss after elective cesarean deliveries using the new standardized oxytocin protocol versus the historically unregimented, high-dose strategy. A secondary outcome was the incidence of postpartum hemorrhage, defined as quantitative blood loss greater than 1 l at the time of calculation.

METHODS: This single-center, retrospective cohort study compared quantitative blood loss in healthy parturients undergoing elective cesarean deliveries under neuraxial anesthesia that received either high-dose oxytocin (40 international units [IU]) given over an unregulated amount of time via wide open IV infusion (Group H), or a low-dose oxytocin protocol (Group L): 3 IU of oxytocin administered over 3 min, with a second 3 IU bolus if inadequate tone, then oxytocin infused at 18 IU/h for 1 h followed by 3.6 IU/h for 3 h. Exclusion criteria included failed labor induction converted to cesarean delivery, high-risk pregnancy (placental abnormalities, maternal bleeding disorders, gestational hypertension, and pre-eclampsia), those who received general anesthesia, and multiple gestation pregnancies.

RESULTS: Sixty-two patients were included for analysis in Group H, and thirty-seven in Group L. A multivariate linear regression model controlling for patient age, gestational age at time of delivery, cesarean section indication, and hemorrhagic medications given found the regimen of oxytocin a patient received did not predict their blood loss (R2 = 0.08, adjusted R2 of -0.003, P = .48). Additionally, the low-dose group had less blood loss by estimated marginal means (769 mL, 95% CI, 526-1011, versus 944 ml, 95% CI, 724-1164, P = .14). The incidence of postpartum hemorrhage was 21.0% in Group H and 13.5% in Group L, P = .09.

CONCLUSIONS: This study concludes the low-dose oxytocin protocol released in the Defense Health Agency hemorrhage bundle does not correlate with increased blood loss due to uterine atony when compared to a high-dose strategy for an elective, low-risk cesarean delivery. Future research should be aimed at capturing the side effect profile of this oxytocin dosing strategy, quantitative blood loss analyses in high-risk patients, and its effect on blood transfusion rates.