Haemodynamic effects of carbetocin and oxytocin given as intravenous bolus on women undergoing caesarean delivery: a randomised trial

Objective: This study compares the maternal heart rate effects of carbetocin and oxytocin during elective caesarean delivery.

Design: Double blind randomised single centre study (1:1).

Setting: University hospital providing intrapartum care.

Population: Fifty-six women undergoing elective caesarean section after spinal anaesthesia.

Methods: Haemodynamic parameters were measured non-invasively using the Task Force(®) Monitor 3040i system. Measurements were taken for 500 seconds upon administration of a slow intravenous bolus of the clinically recommended doses of 100 μg of carbetocin or 5 IU of oxytocin to prevent postpartum haemorrhage (PPH).

Main outcome measure: Effect on maternal heart rate (HR).

Results: Statistically indistinguishable haemodynamic effects were seen for both drugs, with a maximal effect at about 30-40 seconds: HR increased 17.98 ± 2.53 bpm for oxytocin and 14.20 ± 2.45 bpm for carbetocin. Systolic blood pressure (sBP) decreased (-26.80 ± 2.82 mmHg for oxytocin versus -22.98 ± 2.75 mmHg for carbetocin). Following the maximal effect, women treated with carbetocin recovered slowly to baseline values asymptotically (HR and BP), whereas women treated with oxytocin displayed a slight rebound bradycardia at 200 seconds (-6.8 ± 1.92 bpm). Patients under both treatments showed a similar profile of side effects without any indication of unexpected adverse effects.

Conclusion: Both oxytocins have comparable haemodynamic effects and are uterotonic drugs with an acceptable safety profile for prophylactic use. Minimal differences in the recovery phase beyond 70 seconds are in keeping with the fact that carbetocin has an extended half-life compared with oxytocin.