Purpose Oxytocin is the first-line agent to prevent and treat uterine atony during cesarean delivery (CD). We compared the effective dose in 50% of the parturients (ED 50 ) of a prophylactic oxytocin bolus during CD in young (<35 years) and old parturients (≥35 years) using Dixon’s up-and-down method. Patients and Methods Twenty-eight young parturients (young group) and 25 old parturients (old group) undergoing CD under combined spinal-epidural anesthesia were enrolled. The initial oxytocin bolus was 0.5 IU, with increments or decrements of 0.25 IU. Maternal adverse effects, requirement for additional uterotonic agents, and estimated blood loss were recorded. Results The ED 50 for oxytocin in the old group was higher than that in the young group (1.41 IU; 95% confidence interval, 0.63–2.19) vs 0.66 IU (0.04–1.29), P < 0.001). The total oxytocin dose in the old group was higher than in the young group (5.9 ± 2.9 vs 4.1 ± 2.1 IU, P = 0.01). The estimated blood loss in the older group and young group was 401.2 ± 204.5 mL and 289.3 ± 104.6 mL, respectively ( P =0.01). The overall prevalence of adverse effects was higher in the old group than in the young group (68.0% vs 21.4%, P < 0.001). Conclusion The initial bolus and total requirement of oxytocin for preventing uterine atony were higher in old parturients than in young parturients during CD. Advanced maternal age may necessitate higher doses of oxytocin.

No abstract

Background: An estimate of 90% effective dose (ED90) of oxytocin infusion has already been proved effective in non-laboring parturients. However, the requirements of oxytocin for elderly parturients with prior history of cesarean delivery (CD) may be higher. The aim of this study was to find the optimum oxytocin infusion rate for preventing uterine atony during CD in elderly parturients with prior history of CD.Method: We performed a randomized, double-blinded study in 120 healthy elderly parturients with prior history of CD scheduled for elective CD under combined spinal–epidural (CSE) anesthesia. Participants were treated with oxytocin infusion randomly at the rates of 0, 4, 8, 12, 16, or 20 IU h−1 after the delivery of infants. Following oxytocin administration, a blinded obstetrician evaluated the uterine tone (UT), verbally describing it using numerical scales (0–10: 0, no UT; 10, optimal UT) as either adequate or inadequate at the time intervals of 3, 6, and 9 min. Maternal adverse effects, requirements for additional uterotonic agents, delivery–placenta delivery time (PD), and estimated blood loss (EBL) were recorded.Results: The 50% effective dose (ED50) and 90% effective dose (ED90) of oxytocin infusion were 14.6 IU h−1 (95% confidence interval 12.0–18.4 IU h−1) and 27.7 IU h−1 (95% confidence interval 22.5–39.4 IU h−1), respectively. As the rate of infusion was increased in parturients, the rescue oxytocin dose and delivery-PD time were decreased. Parturients who received 0 IU h−1 oxytocin at 3, 6, and 9 min obtained lower UT scores than those who received 16 and 20 IU h−1 oxytocin (p &lt; 0.05, respectively). No significant differences were observed among groups in EBL and maternal adverse effects.Conclusion: The infusion rate of oxytocin at 14.57 and 27.74 IU h−1 produces adequate UT in 50% and 90% of elderly parturients with prior history of CD, respectively. An oxytocin infusion rate of 27.7 IU h−1 is suggested to be the optimal dose for preventing uterine atony during CD in elderly parturients with prior history of cesarean delivery.Clinical Trial Registration: [https://www.chictr.org.cn/bin/project/edit?pid=62489], Identifier: [ChiCTR2000038891].