Carbetocin at elective cesarean delivery: a dose-finding study
Abstract Number: 85
Abstract Type: Original Research
Introduction: Carbetocin is a synthetic oxytocin analogue that binds to oxytocin receptors with higher affinity. It lasts 4-7 times longer than oxytocin, with a similar side effect profile and greater apparent efficacy (1). Its onset time and duration after IV injection are 2 and 60 minutes respectively (1, 2). The Society of Obstetricians and Gynecologists of Canada (SOGC) recommends a single IV bolus dose of carbetocin 100 μg at elective cesarean delivery (CD) in lieu of oxytocin regimens (3).However, there is no published data on how this dose was determined. The goal of this study is to determine the minimum dose of carbetocin required to produce appropriate uterine contractility in 95% of women undergoing elective CD.
Methods: With REB approval and informed consent, we conducted a double blind, randomized, dose-finding study. We recruited patients at low risk for PPH undergoing elective CD under spinal anesthesia. Patients were allocated to receive a bolus of 80, 90, 100, 110 or 120 μg of carbetocin upon delivery. The efficacy of the uterine contraction was evaluated by the obstetrician. If unsatisfactory, oxytocin infusion was initiated and additional uterotonics were administered as necessary. The primary outcome was satisfactory uterine contraction at two minutes after delivery. Secondary outcomes included the use of additional uterotonics within the first two hours, the estimated blood loss based on hematocrit variation, and side effects.
Results: Twenty-eight patients out of the planned 80 have been recruited from November 17, 2010 to January 14, 2011. Overall 24 (85.7%) of the patients have presented satisfactory uterine contraction within two minutes of carbetocin administration. However, only 2 (7.1%) required additional oxytocin infusion within the first two hours. The average estimated blood loss was 499.1 ± 419.9 ml. The incidence of side effects is presented in the table.
Discussion: The response to carbetocin was as expected for the dose range used and the ED95 will be calculated at the end of recruitment. Side effects were similar to those observed with oxytocin, however the incidence of flushing seems lower. Blood loss was comparable to previous data.
References: 1) Eur J Obstet Gynecol Reprod Biol 2009;147:15-20; 2) Cochrane Database of Systematic Reviews 2007;(3):CD005457; 3) J Obstet Gynecol Can 2009; 31:980-93.