Higher-Dose Oxytocin and Hemorrhage After Vaginal Delivery

Abstract

Objective Higher-dose oxytocin is more effective than lower-dose regimens to prevent postpartum hemorrhage following cesarean delivery. We compared two higher-dose regimens (80U and 40U) to our routine regimen (10U) among women who delivered vaginally. Methods In a double-masked randomized trial, oxytocin (80U, 40U or 10U) in 500ml was given over 1 hour after placental delivery. The primary outcome was a composite: any treatment of uterine atony or hemorrhage. Prespecified secondary outcomes included outcomes in the primary composite and a decline of 6% or greater in hematocrit. A sample size of 600 per group (N=1800) was required to compare each of the 80U and 40U to the 10U group. At planned interim review (n=1201), enrollment in the 40U group was stopped for futility and enrollment continued in the other groups. Results Of 2,869 women, 1,798 were randomized: 658 to 80U, 481 to 40U and 659 to 10U. Most characteristics were similar across groups. The risk of the primary outcome in the 80U group (6%; RR 0.93, 95% CI: 0.62–1.40) or the 40U group (6%; 0.94, 0.61–1.47) was not different compared with the 10U group (7%). Treatment with additional oxytocin after the first hour was less frequent with 80U compared with 10U (RR 0.41; 0.19–0.88) as was a 6% or greater decline in hematocrit (0.83; 0.69–0.99); both outcomes declined with increasing oxytocin dose. Outcomes were similar between the 40U and 10U groups. Conclusion Compared with 10 units, 80 or 40 units of prophylactic oxytocin did not reduce overall postpartum hemorrhage treatment when given in 500ml over 1 hour for vaginal delivery. Eighty units decreased the need for additional oxytocin and the risk of a 6% or greater decline in hematocrit.

Risk factors for uterine atony/postpartum hemorrhage requiring treatment after vaginal delivery

“…20 The prevalence of this outcome by categories of each of the 21 potential risk factors for uterine atony/hemorrhage and the corresponding unadjusted OR (95% CI) are presented in Table 2. BMI, race/ethnicity, labor induction, twins, preeclampsia, breastfeeding, anemia, protracted 2 nd stage, and chorioamnionitis were significantly associated with postpartum atony or hemorrhage in univariate analyses.…”

“…20 The primary aim of the trial was to evaluate higher doses of oxytocin compared to a standard low dose oxytocin regimen used for prophylaxis among women undergoing vaginal delivery. Women were randomized to a 10 unit (standard), 40 unit, or 80 unit dose regimen of oxytocin at vaginal delivery.…”

Prevention and Management of Postpartum Haemorrhage

“…An RCT, using a primary outcome of any treatment of uterine atony or haemorrhage, assessed whether or not a higher dose of oxytocin after vaginal delivery was more effective than a low‐dose regimen in preventing PPH after a vaginal delivery. Compared with 10 iu, administering 40 iu or 80 iu of prophylactic oxytocin did not reduce overall PPH treatment when given in 500 ml over 1 hour for vaginal delivery.…”

Effect of a High-Rate Versus a Low-Rate Oxytocin Infusion for Maintaining Uterine Contractility During Elective Cesarean Delivery: A Prospective Randomized Clinical Trial

“…Based on data from prior studies, 5,6,11,15–17 the selected oxytocin infusion rates were decided a priori by consensus. Opaque envelopes containing group assignments ensured blinding of study investigators, and members of the anesthesia and surgical teams.…”