Jinping Liu,1,* Zhimin Sheng,2,* Feihe Guo,1 Xiao Lin,1 Li Xu,3 Lihong Sun,1 Xiaowei Qian1 

1Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, People’s Republic of China; 2Department of Anesthesiology, Wenling Maternal and Child Health Care Hospital, Taizhou, People’s Republic of China; 3Department of Ultrasonography, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Lihong Sun; Xiaowei Qian, Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Xueshi Road 1, Hangzhou, Zhejiang Province, 310006, People’s Republic of China, Tel +86-571-87061501, Fax +86 571 87061878, Email sunlihong@zju.edu.cn; qianxw@zju.edu.cn

Purpose: Spinal anesthesia-induced hypotension can cause detrimental effects on both the mother and the fetus, and it remains a significant concern in obstetric anesthesia. The use of vasopressors is considered the most reliable and effective approach. Previous studies have shown that norepinephrine appears to be superior to phenylephrine in maintaining maternal heart rate and cardiac output. Therefore, we hypothesize that norepinephrine is more effective than phenylephrine in maintaining neonatal cerebral perfusion when used to prevent spinal anesthesia-induced hypotension.
Patients and Methods: This study is a prospective, double-blinded, randomized trial. We enrolled 216 singleton parturients who were scheduled for elective cesarean delivery. The patients received a prophylactic intravenous infusion of either norepinephrine (0.08 μg/kg/min) or phenylephrine (0.5 μg/kg/min). Maternal cardiac output was not routinely monitored during the study period. Fetal ultrasound examinations were performed, with blood velocity measured in the middle cerebral artery and umbilical artery, and the cerebroplacental ratio calculated.
Results: Ninety subjects were ultimately analyzed in each group. The changes in blood velocity in the middle cerebral artery and umbilical artery, as well as the calculated cerebroplacental ratio at 3 and 6 minutes after spinal anesthesia, did not differ significantly between the two groups. The estimated difference of ΔCPR in two groups was - 0.01 (95% CI, − 0.05– 0.02, P = 0.491) at 3 minutes and was 0.02 (95% CI, − 0.01– 0.07, P = 0.204) at 6 minutes.
Conclusion: Prophylactic infusion of norepinephrine or phenylephrine at comparable doses has similar effects on fetal cerebral perfusion.

Keywords: norepinephrine, phenylephrine, hypotension, fetal cerebral perfusion