ST depression at caesarean section and the relation to oxytocin dose. A randomised controlled trial
Article first published online: 6 JUL 2010
© 2010 The Authors Journal compilation © RCOG 2010 BJOG An International Journal of Obstetrics and Gynaecology
BJOG: An International Journal of Obstetrics & Gynaecology
Volume 117, Issue 9, page 1165, August 2010
How to Cite
Butwick, A. and Dyer, R. (2010), ST depression at caesarean section and the relation to oxytocin dose. A randomised controlled trial. BJOG: An International Journal of Obstetrics & Gynaecology, 117: 1165. doi: 10.1111/j.1471-0528.2010.02625.x
- Issue published online: 6 JUL 2010
- Article first published online: 6 JUL 2010
- Accepted 31 March 2010.
We read with interest the study by Jonsson et al.1 and wish to comment on the authors’ conclusions.
The authors correctly state in the introduction that the cardiovascular side effects of oxytocin are dose-related. However, the use of 5 iu oxytocin is recommended for patients undergoing caesarean delivery by a number of regulatory societies (National Collaborating Centre for Women’s and Children’s Health; National Institute for Health and Clinical Excellence; and the Royal College of Obstetricians and Gynaecologists).2 Further explanation is needed to justify the use of 10 iu oxytocin in this study, as Butwick et al. and Carvalho et al.3,4 have shown that oxytocin doses of less than 5 iu are effective in achieving adequate uterine tone during elective caesarean delivery.
The interim analysis indicated a high prevalence of ST depression (24%) in patients receiving 10 iu oxytocin. Why was the study not stopped at this time because of the observed adverse effects associated with this higher dose? In addition, the authors provide limited statistical data to validate their recruitment of an additional 50 patients following interim analysis. Their results indicate that the differences in proportion of patients with ST depression associated with oxytocin bolus between groups only barely met the criteria for statistical significance (P = 0.046).
Tachycardic responses resulting from the anticholinergic effects of atropine may have contributed to ST changes. Atropine use was relatively high in each group; however, no information of the timing of atropine administration is provided. Furthermore, the use of additional oxytocin doses and other uterotonics (in the 5-iu oxytocin group) also limits direct comparisons of ST changes between 5 and 10 iu oxytocin.
Peak effects on ST changes may have occurred earlier than reported in the study, as Dyer et al. and Svanstrom et al.5,6 have shown that peak peripheral vascular effects and electrocardiogram (ECG) changes are observed within 60 seconds of the administration of oxytocin.
Despite these apparent limitations, this study adds to current evidence supporting the use of a bolus of ≤5 iu oxytocin during elective caesarean delivery, so as to minimise cardiovascular oxytocin-related side effects. Future work should focus on investigating optimal oxytocin infusions for the maintenance of adequate uterine tone following oxytocin bolus administration. We question whether there is relevant scientific justification for further investigations of the administration of >5 iu oxytocin for patients undergoing elective caesarean delivery.