• Gary Tran, Marcelo Kanczuk, and Mrinalini Balki.
• Faculty of Medicine, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada.
• Can J Anaesth. 2017 Aug 1; 64 (8): 820-827.

PurposeProlonged exposure to oxytocin during augmentation of labour is associated with uterine atony and an increased risk of postpartum hemorrhage (PPH) due to oxytocin receptor desensitization. Cessation of oxytocin infusion during labour may facilitate recovery of oxytocin receptor function, which then helps to restore myometrial contractility and decrease postpartum blood loss. We examined the association between oxytocin recovery interval, i.e., the time from discontinuing oxytocin to Cesarean delivery (CD) for labour arrest, and blood loss.MethodsThis retrospective cohort study included women who underwent CD for labour arrest following oxytocin-augmented labour from July 1, 2013 to July 19, 2015 at our institution. Data were collected on patient demographics, labour and delivery characteristics, oxytocin induction and augmentation, recovery interval, and PPH risk factors. The primary outcome was estimated blood loss (EBL), calculated using the hematocrit variation method.ResultsData on 490 women were analyzed. The mean (standard deviation) EBL was 1,341 (577) mL; the amount of oxytocin administered during labour was 6,447 (6,868) mU, and the oxytocin recovery interval was 99 (65) min. Every ten-minute increase in the recovery interval was associated with a 10-mL decrease in EBL (95% confidence interval [CI], -18 to -3; P = 0.009). Morbidly obese women had a significantly higher EBL than those with a body mass index < 40 kg·m-2 (mean difference, 572 mL; 95% CI, 382 to 762; P < 0.001). The amount and duration of oxytocin administered during labour, but not the oxytocin recovery interval, was associated with the use of additional interventions to control PPH (P = 0.005).ConclusionOur study shows that an increase in the oxytocin recovery interval is associated with a decrease in blood loss at CD in women with oxytocin augmented labour. These data support discontinuing the oxytocin infusion as soon as the decision is made to proceed with CD for labour arrest, particularly in morbidly obese women.

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