An observational cohort study of 3 units versus 5 units slow intravenous bolus oxytocin in women undergoing elective caesarean delivery.

This study sought to compare postpartum blood loss and maternal outcomes after 3IU and 5IU oxytocin at elective caesarean delivery. In a prospective observational study, 73 women undergoing elective caesarean delivery under spinal anaesthetic received a slow I.V. injection of either 3IU (n = 35) or 5IU (n = 38) oxytocin after delivery. The main outcome was gravimetrically measured 24-hour postpartum blood loss with a non-inferiority margin of 300 mL. Uterine tone, phenylephrine dose, emesis and hypotension after oxytocin administration were secondary outcomes. Gravimetric postpartum blood loss was lower in the 3IU group (-58.8 mL [95% CI: -212.1, 94.3]) after adjusting for BMI, pre-delivery vasopressor dose, parity, and risk of uterine atony, with the upper confidence limit below the 300 mL margin in support of non-inferiority. Patients receiving 3IU had a higher (non-significant) rate of having post-delivery phenylephrine to treat hypotension (RR = 1.59 [95% CI: 0.97, 2.63]), but of those treated, the 3IU group required significantly less (-427 mcg [95% CI: -740, -114]). The 3IU group had a lower prevalence of vomiting compared to those receiving 5IU (6% versus 24%; P = 0.047). Administration of 3IU oxytocin was non-inferior compared to standard 5IU with respect to blood loss in women undergoing elective caesarean delivery.