Exploring cardiac effects after oxytocin 2.5 IU or carbetocin 100 µg: A randomised controlled trial in women undergoing planned caesarean delivery.

BACKGROUND: Oxytocin can stimulate release of myocardial biomarkers troponin I and T, prolong QTc and induce ST-depression. OBJECTIVE: To explore cardiac changes after either intravenous carbetocin or oxytocin. STUDY DESIGN: Exploratory phase 4 randomised controlled trial. SETTING: Obstetrics units of Oslo University Hospital, Norway between September 2015 and May 2018. PARTICIPANTS: Forty healthy, singleton pregnant women aged 18 to 50 years at gestational age at least 36 weeks with a planned caesarean delivery. INTERVENTIONS: Participants were randomised to receive either oxytocin 2.5 IU or carbetocin 100 µg immediately after delivery. MAIN OUTCOME MEASURES: The primary endpoint was the assessment of troponin I within 48 h of study drug administration. Troponin I and T, and creatine kinase myocardial band assessments were measured before spinal anaesthesia (baseline), and again at 4, 10 and 24 h after delivery. QTc, ST-depression and relative increase in heart rate were recorded from start of study drug administration to 10 min after delivery. All adverse events were monitored. RESULTS: Compared with the carbetocin group, higher troponin I levels were observed in the oxytocin group at 4 h and 10 h after delivery. For both treatment groups, an increase from baseline in troponin I and T was most pronounced at 10 h after delivery, and it had begun to decline by 24 h. QTc increased with time after administration of both study drugs, with a mean maximum increase of 10.4 ms observed at 9 min (P   <  0.001). No statistical differences were observed in QTc ( P  = 0.13) or ST-depression ( P  = 0.11) between the treatment groups. CONCLUSIONS: Oxytocin 2.5 IU and carbetocin 100 µg caused a similar increase in QTc. The trial was underpowered with regards to ST-depression and the release of myocardial biomarkers and these warrant further investigation. Data from this trial will inform a larger phase 4 trial to determine potential drug differences in troponin release. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02528136.