Effects of Prophylactic Infusion of Norepinephrine on Parturients and Fetus Under Spinal Anesthesia for Cesarean Section

OBJECTIVE To investigate the effects of prophylactic infusion of norepinephrine on parturients and fetus under spinal anesthesia for caesarean section. METHODS One hundred and sixty full-term parturients with American Society of Anesthestists classification I-Ⅱand singletonu ndergoing elective cesarean delivery under spinal anesthesia were randomly divided into two groups(n=80):norepinephrine group and phenylephrine group. The parturients received prophylactic infusion of either 0.5 μg·kg^-1·min^-1 phenylephfine or 0.05 μg·kg^-1·min^-1 norepinephrine when starting intrathecal injection. The vasopressor infusion was stopped when the systolic blood pressure(SBP) >140 mmHg. The SBP, diastolic blood pressure(DBP), heart rate(HR), cardiac output(CO) and systemic vascular resistance(SVR) were carried out. The fetal heart rate was monitored. The umbilical artery blood was collected to analysis after baby delivery and Apgar scores were assessed. The adverse reactions(such as hypotension, sinus bradycardia, nausea and vomiting, fetal distress, etc.) of parturients and fetus were recorded also. RESULTS Compared with the phenylephrine group, SBP, HR, and CO were increased, SVR were lower at skin incision(t₂) and delivery of baby(t₃), but there were no significant differences in SBP, DBP, HR, CO and SVR at other time points. The incidence of maternal bradycardia was lower in the epinephrine group, but there was no significant difference in the incidence of hypotension, nausea and vomiting between the two groups. There were no significant difference in pH of umbilical artery between the 2 groups. CONCLUSION Compared with phenylephrine, prophylactic infusion of norepinephrine can increase blood pressure and CO, decrease the incidence of bradycardia during cesarean section under spinal anesthesia, but can't reduce the incidence of hypotension, nausea and vomiting.