Norepinephrine versus phenylephrine affects prethrombotic response in patients undergoing cesarean section under spinal anesthesia: a randomized, double-blind, controlled study

Background: Venous thromboembolism (VTE) is one of the most common and serious complications of cesarean section in parturients. Norepinephrine (NE) has been shown to activate coagulation. The aim of this study was to compare the effect of a fixed-rate prophylactic norepinephrine infusion and a fixed-rate prophylactic phenylephrine（PHE） infusion under spinal anesthesia for caesarean section on the prethrombotic response. Materials and methods: Sixty-six women undergoing cesarean section under spinal anesthesia were randomly assigned to the NE group or PHE group, starting simultaneously with the administration of the subarachnoid solution, a “study drug” solution containing either NE or PHE was pumped intravenously at a constant rate of 15 ml/h until the end of the operation. Plasma coagulation factor VIII activity (FVIII: C), Fibrinogen, and D-dimer levels were measured in blood samples obtained on admission to the operating theatre and at the end of the procedure. Results: Compared with preoperative levels, there were no significant differences in postoperative fibrinogen and D-dimer levels in the NE group, except for a decrease in FVIII: C levels ( P = 0.003). However, postoperative levels of FVIII: C ( P = 0.009), fibrinogen ( P = 0.035) and D-dimer ( P = 0.025) were increased in the NE group compared with postoperative levels in the PHE group. Conclusions: NE does not affect the maternal prethrombotic response and can be safely used in cesarean sections. Compared with PHE infusion, NE infusion increased the level of coagulation molecules, suggesting that NE maybe more beneficial for women with high intraoperative bleeding requiring hemostasis.