Postpartum uterine atony and hemorrhage can be effectively prevented with the use of oxytocin, but the optimal dosage and route of administration have not been established. The danger of blood loss is particularly severe following cesarean delivery. Munn and colleagues studied the ability of high-dose oxytocin to prevent uterine atony in women at cesarean delivery.

All women undergoing cesarean delivery at a university hospital between 1997 and 1999 were invited to participate in the randomized, double-masked study. Women who had not experienced labor prior to cesarean delivery were excluded. At the time of surgery, patients received either low-dose (333 mU per minute) or high-dose (2,667 mU per minute) oxytocin solutions infused over 30 minutes following delivery of the infant. At the discretion of the surgeons, additional uterotonic agents could be given. Oxygen saturation and blood pressure were monitored in the post-anesthesia care unit.

The 163 women randomized to low-dose oxytocin were comparable to the 158 assigned to high-dose therapy in terms of maternal characteristics and indications for cesarean delivery. The groups were also comparable in operative characteristics such as duration and types of surgery and anesthesia. Additional uterotonic agents were required by 39 percent of women in the low-dose group compared with 19 percent of those in the high-dose group. No cases of unexplained hypotension occurred. Women with labor arrest and women with chorioamnionitis were more likely than other women to receive additional uterotonic agents. After controlling for these factors, women in the high-dose group still had a significantly lower rate of receiving additional uterotonic therapy.

The authors conclude that, at cesarean delivery, high-dose oxytocin more effectively prevents uterine atony than low-dose oxytocin. Reduced need for second-line uterotonic agents has the potential of avoiding side effects such as hypertension or bronchospasm and may also lead to cost savings.