Study Provides Dosing Insight for Oxytocin in Preventing Obstetric Hemorrhage

Despite the widespread use of oxytocin as a prophylactic for obstetric hemorrhage, there is no clear recommendation as to the optimal dose. To provide insight into this issue, researchers conducted a double-masked randomized trial comparing two higher dose regimens with a standard dose regimen. Their results were published in a recent issue of Obstetrics & Gynecology.

Dr. Alan T.N. Tita, associate professor in the department of obstetrics and gynecology at University of Alabama at Birmingham, Birmingham, Alabama, and colleagues randomized 1,798 women with viable pregnancies undergoing vaginal delivery at 24 weeks of gestation or more to receive oxytocin at doses of 80 units (N=658), 40 units (N=481), or 10 units (N=659).

In comparison with the participants who received 10 units, Tita et al. found that higher doses did not result in a significant decrease in the unadjusted risk of the primary outcome (i.e., a composite of any treatment of uterine atony or hemorrhage) nor a decrease in the treatment of uterine atony or obstetric hemorrhage with any uterotonics. The researchers found a relative risk of 6% for both of the higher doses as compared to 7% for the 10 unit dose. However, Tita and colleagues noted that, when compared with 10 units of oxytocin, 80 units significantly decreased the need for treatment with additional oxytocin. They did not find the same association with 40 units of oxytocin. In addition, fewer women in the group who received 80 units had a 6% or greater decline in hematocrit as compared with the group who received 10 units; a similar association was not found with the group who received 40 units. Higher doses were not associated with higher incidences of such adverse effects as hypotension or fluid overload.

Although higher doses of oxytocin appear to be more effective than lower-dose regimens in preventing postpartum hemorrhage after cesarean delivery, the researchers believe their findings do not show that this is the case for women with vaginal deliveries. However, Tita et al. found some benefits associated with the 80 unit dose.

“Overall, higher doses of prophylactic oxytocin (80 units or 40 units), as compared with the standard dose of 10 units of oxytocin when administered in 500 mL of crystalloid over the course of 1 hour after vaginal delivery, did not significantly reduce the incidence of the primary composite outcome of uterine atony or hemorrhage requiring any treatment,” Tita and colleagues explained. “However, 80 units of oxytocin reduced the frequency of two prespecified secondary outcomes: hemorrhage requiring treatment after the first postpartum hour and a decline in hematocrit more than 6% units. There was a significant dose-response trend in these outcomes (reducing incidence with increasing dose of prophylactic oxytocin).”

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References:

Reference:
Tita AT, Szychowski JM, Rouse DJ, et al. Higher-dose oxytocin and hemorrhage after vaginal delivery: a randomized controlled trial. Obstet Gynecol. 2012;119(2 Pt 1):293-300.