Postpartum haemorrhage remains a significant cause of maternal morbidity and mortality with the commonest reason being uterine atony. For prevention of uterine atony during caesarean delivery, oxytocin is advocated as a first line drug. There is however no published data regarding utility of a weight-based oxytocin infusion. The present study evaluated dose-response relationship for oxytocin infusion when used as weight-based regimen. A total of 55 non-labouring patients without risk factors for uterine atony and scheduled for caesarean delivery under spinal anaesthesia were enrolled. Randomization was done to receive oxytocin infusion in a dose of 0.1, 0.15, 0.2, 0.25 or 0.3 IU kg-1 h-1 (n = 11 each), initiated at the time of cord clamping and continued until the end of surgery. Successful outcome was defined as attaining an adequate uterine response at 4 min of initiation of infusion and maintained till end of surgery. Oxytocin associated hypotension, tachycardia, ST-T changes, nausea/vomiting, flushing and chest pain were also observed. A significant linear trend for adequate intraoperative uterine tone was seen with increasing dose of weight-based oxytocin infusion (P < 0.001). The effective dose in 90% population (ED90) was 0.29 IU kg-1 h-1 (95% CI = 0.25-0.42). Amongst the oxytocin associated side effects, a significant linear trend was seen between increasing dose of oxytocin infusion and hypotension as well as nausea/vomiting (p = 0.016 and 0.023 respectively). Thus, oxytocin infusion during caesarean delivery may be used as per the patient's body weight.
Keywords: cesarean delivery; minimum effective dose; oxytocin; uterine tone; weight-based dose.
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