Objective To investigate the dose-effect of defensive infusion of norepinephrine to maintain hemodynamic stability during cesarean section under combined spinal epidural anesthesia.

Methods A total of 100 pregnant women undergoing cesarean section from January 2020 to April 2021 were selected as study objects. They were divided into control group (group C, no norepinephrine was used), NE_0.025 groupuse of norepinephrine for 0.025 μg/(kg·min), NE_0.05 groupuse of norepinephrine for 0.025 μg/(kg·min), NE_0.075 groupuse of norepinephrine for 0.075 μg/(kg·min), NE_0.10 groupuse of norepinephrine for 0.10 μg/(kg·min)according to random number table method, with 20 cases in each group. After local anesthetic injection, NE_0.025 group, NE_0.05 group, NE_0.075 group and NE_0.10 group were continuously infused norepinephrine for 0.025 μg/(kg·min), 0.05 μg/(kg·min), 0.075 μg/(kg·min) and 0.10 μg/(kg·min), respectively. Occurrence of hypotension, bradycardia, hypertension, nausea and vomiting were recorded.

Results Compared with group C, NE_0.05, NE_0.075 and NE_0.10 groups had lower incidence of hypotension, nausea and vomiting (P < 0.05). The 50% effective doses (ED₅₀) and effective doses (ED₉₅) values of defensive norepinephrine infusion were 0.042 μg/(kg·min) and 0.099 μg/(kg·min), respectively. Log-rank test showed that the incidence rates of hypotension in different anesthetic dose groups showed significant differences compared with that in group C (χ²=40.759, P < 0.05).

Conclusion Defensive infusion of norepinephrine could maintain hemodynamic stability during cesarean section under combined epidural and lumbar anesthesia.