Purpose: A randomized study involving pregnant women was conducted to compare the effectiveness of a single intravenous (IV) injection of carbetocin with that of a standard 2-h oxytocin IV infusion with respect to intraoperative blood loss in the prevention of uterine atony after cesarean section (CS). The two treatments also were compared for safety and ability to maintain adequate uterine tone and to reduce the incidence and severity of postpartum hemorrhage (PPH) in women at risk for this condition.
Methods: Between 1 September 2007 and 5 January 2008, we enrolled 104 patients with at least one risk factor for PPH undergoing CS in a randomized, controlled clinical trial. We compared the effect of a single 100 microg IV dose of carbetocin with that of a standard 2-h ten international units (IU) IV infusion of oxytocin. The primary outcome was the proportion of patients requiring additional oxytocic intervention for uterine atony. Fiftytwo women received 100 microg carbetocin IV immediately after placental delivery, while 52 women received 10 IU oxytocin IV infusion. Complete blood count was collected at entry and 24 h postpartum. All outcome measures, including the need for additional uterotonic agents or uterine massage, and blood loss, were analyzed using chi-square, Fisher exact, and Student's t tests.
Results: A single 100 microg IV injection of carbetocin was as effective as a continuous 2-h infusion of oxytocin in controlling intraoperative blood loss after placental delivery. Mean blood loss after carbetocin administration was 30 ml less than after oxytocin administration (P = 0.5). The percentage of patients with blood loss < or =500 ml was greater with carbetocin (81 vs. 55%; P = 0.05). Carbetocin enhanced early postpartum uterine involution. The fundus was below the umbilicus in more patients who received carbetocin at 0, 2, 6, and 24 h on the ward (P < 0.05). The main additional uterotonic agent used was a further administration of oxytocin (20 IU in physiological solution 500 ml at an infusion rate of 200 ml/h). In the carbetocin group, 20 of the 52 women (38.4%) required at least one uterine massage compared to 30 of the 52 women (57.7%) in the oxytocin group (P < 0.01). Overall, uterotonic intervention was clinically indicated in two of the women (3.8%) receiving carbetocin compared to five of the women (9.6%) given an IV oxytocin infusion (P < 0.01). The odds ratio of treatment failure requiring oxytocic intervention was 1.83 (95% confidence interval, CI, 0.9-2.6) times higher in the oxytocin group compared with the carbetocin group.
Conclusions: Carbetocin makes possible to obtain, with a single IV injection, results equivalent to those of oxytocin on the maintenance of uterine tonicity and the limitation of blood losses, in the peri- and in the post-operative period, during a delivery by CS. It has in addition a comparable tolerance. Even in our series adverse events are practically of the same type and similar frequency in both study groups. Thus, the effectiveness of carbetocin consists, thanks to its long half-life, on an unique injection, whereas oxytocin requires repeated injections or a perfusion of several hours, with a variability of the administered doses.