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. INVENTIONS Participants were randomised to receive either oxytocin 2.5 IU or carbetocin 100 mu g 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 mu g 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.

Automated summary

This study explored the cardiac changes after intravenous carbetocin or oxytocin administration. Both drugs were found to cause similar increases in QTc. However, the study was underpowered for ST-depression and the release of myocardial biomarkers, requiring further investigation.