The Effect Of Intravenous Norepinephrine On The Parturient Women's Blood Pressure And Heart Rate In Cesarean Delivery Under Spinal Anesthesia As Well As Neonatal Outcomes

Objective: To compare the effects of norepinephrine and phenylephrine on blood pressure,heart rate of parturients and neonates during cesarean sectionunder spinal anesthesia,and to evaluate the safety of norepinephrine.Methods: In this randomized controlled study,100 parturients scheduled for elective cesarean section were randomly divided into two groups,50 cases in each group: intravenous norepinephrine(group N)and intravenous phenylephrine(group P).The baseline of blood pressure and heart rate were measured when the parturients in the operating room.Spinal anesthesia was performed at the L2-3 or L3-4 interspace with 0.75% isobaric bupivacaine 9 mg and morphine 200?g.In addition,patients received infusion of hydroxyethyl starch 500 ml that was given rapidly after intrathecal drug injection,and SBP and HR were measured and recorded every minute after spinal anesthesia.If SBP recorded two consecutive times decreased below 80% of baseline or 90 mm Hg with single time,the parturients were treated with intravenous norepinephrine 5 ?g in group N or phenylephrine 50 ?g in group P.The time of the fetus took out to intrathecal injection and the uterus opened were also recorded.The interventions of phenylephrine,norepinephrine and atropine were recorded.Reactive hypertension,nausea,vomiting and sinus bradycardia(HR less than 60 bpm)were recorded after intravenous norepinephrine or phenylephrine.Apgar scores at 1 and 5 minute and umbilical cord blood gas values were compared between the two groups.Results: There were no significantly differences in maternal age,gestational age,body weight,height,the highest anesthesia sensory plane at 10 min,bleeding loss and neonatal weight between the two groups(P>0.05).Hypotension were occurred at 6 min and 13 min in group P and at 6 min,10 min,15 min in group N after intrathecal drug injection.There were significant differences compared with the baseline of SBP(T0)in each group(P<0.05).There were no differences between the phenylephrine and norepinephrine groups in the trend of SBP(P>0.05).Heart rate was increased at 6 min after intrathecal drug injection in two groups,and showed the bigger drop at 8 min in group P.There was significantly difference compared with that in group P.There were no differences between the two groups about interventions of phenylephrine or norepinephrine.There were 10 patients injectedatropine for bradycardia in group P and 2 patients in group N.but the times of atropine injected in group P were more than those in group N.There were no differences between the two groups in reactive hypertension,nausea and vomiting.The times of the fetus took out to intrathecal injection and the uterus opened were no differences between them.Apgar scores were not found lower than 8,and there were no differences between the two groups in Apgar scores at 1 and 5 min.The PH,Pa O2,Pa CO2 and BE in umbilical cord blood gas values of the two groups were all in the normal range,with no differences(P>0.05).Conclusion: Intravenous norepinephrine and phenylephrine could effectively maintain the stability of maternal blood pressure after spinal anesthesia.Norepinephrine may be more advantageous than phenylephrine in maintaining maternal heart rate.There were no adverse effects on neonatal Apgar scores and umbilical venous blood gas.It could be safely used in treatment of hypotension after spinal anesthesia for caesarean section.