Comparison of carbetocin as a bolus or an infusion with prophylactic phenylephrine on maternal heart rate during Cesarean delivery under spinal anesthesia: a double-blinded randomized controlled trial.

Purpose: Carbetocin, an oxytocin analog, given as a postpartum hemorrhage prophylaxis in elective Cesarean deliveries, frequently causes tachycardia and hypotension. Phenylephrine infusion has been shown to prevent spinal anesthesia-induced hypotension. The goal of this study was to evaluate if a slow infusion of carbetocin would reduce maternal heart rate variation and hemodynamic disturbances compared with a rapid bolus in parturients receiving a prophylactic phenylephrine infusion during elective Cesarean delivery.

Methods: In this double-blinded randomized controlled trial, 70 healthy parturients were allocated to either a bolus group or an infusion group. At cord clamping, participants in the bolus group received carbetocin 100 µg as a rapid intravenous bolus, while participants in the infusion group received carbetocin 100 µg over 10 min. The primary outcome was the variation in maternal heart rate from baseline during the 20 min following cord clamping. Secondary outcomes included blood pressure, cardiac output, and stroke volume variations during the study period, measured with the ClearSight™ hemodynamic monitor.

Results: Maximum heart rate variation was not different between the groups: bolus group, mean (standard deviation) 29.8 (25.2)% vs infusion group, 27.2 (23.3)%; P = 0.67. The increase in heart rate occurred significantly earlier in the bolus group than in the infusion group (median [interquartile range] time, 105 [69-570] sec vs 485 [255-762] sec; P = 0.02; group × time interaction: two-way repeated measures ANOVA, P = 0.04). There was no significant difference in maximum variations for the other hemodynamic parameters between the groups.

Conclusion: Carbetocin infused over ten minutes did not reduce the magnitude of maternal heart rate variation but delayed its occurrence. This finding could be relevant to the anesthesiologist caring for parturients in whom a slight increase in maternal heart rate is clinically undesirable.

Study registration: www.

Clinicaltrials: gov (NCT03404544); registered 19 January 2018.