The Median Effective Dose of Oxytocin Needed to Prevent Uterine Atony During Cesarean Delivery in Elderly Parturients

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 (ED50) 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 ED50 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.