To estimate the minimum effective dose of oxytocin required to produce adequate uterine tone in women undergoing elective caesarean delivery

To estimate the minimum effective dose of oxytocin required to produce adequate uterine tone in women undergoing elective caesarean delivery under spinal anaesthesia.
Background
Patients undergoing caesarean delivery are at increased risk of obstetric haemorrhage. Uterine atony has been shown to be most common aetiology (30%) for PPH in patients undergoing caesarean delivery. Use of uterotonic agents decreases the incidence of PPH by approximately 40% when compared with placebo. Oxytocin is the most frequently used uterotonic agent because of less side-effects compared with all other available agents. We did the study to find out the minimal dose of oxytocin required to produce adequate uterine tone (UT) in primigravida women undergoing elective caesarean delivery.
Methods
This randomized double blind study was conducted in ninety full term primigravidas undergoing elective caesarean delivery under spinal anaesthesia. All patients received intravenous bolus of either 0.5, 1, or 2 unit oxytocin followed by infusion of 10 unit/h. UT was assessed by a blinded obstetrician as either adequate or inadequate, and using a five point scale, where 1 = atonic, 2 = partial but inadequate contraction, 3 = adequate contraction, 4 = well contracted and 5 = very well contracted at 2, 3, 6, and 9 min after oxytocin administration. Minimum effective doses of oxytocin were analysed. Oxytocin related side-effects (including hypotension) were recorded.
Results
There were no significant differences in the prevalence of adequate UT among the study groups at 2 min (86%, 90% and 93% for, 0.5, 1 and 2 unit oxytocin, respectively). The prevalence of nausea and vomiting was significantly higher after 2 unit oxytocin vs 0.5 unit at 1 min (13% vs 3%).
Conclusion
Small bolus dosages of oxytocin (0.5–2 unit) result in adequate uterine tone in primigravida women undergoing elective caesarean delivery with minimal effects on haemodynamic parameters and less incidence of nausea and vomiting.