Effects Of Different Infusion Rates Of Norepinephrine On Maternal And Neonatal Outcomes In Cesarean Section Under Combined Spinal-Epidural Anesthesia

Objective:To investigate the effects of different infusion rate of norepinephrine（NE）on hemodynamics,incidence of nausea and vomiting of parturients,neonate umbilical arterial blood gas and Apgar scores at the time of 1 min and 5 min after the neonate was born during combined spinal and epidural anesthesia（CSEA）for elective cesarean section.Methods:After the approval of Jilin University Ethics Committee,Eighty term singleton parturients,ASAⅠ^Ⅱ,having CSEA for elective cesarean section were randomized divided into four groups,20 parturients in each group.Control group（Group C）and experimental group（Group N₁,N₂,N₃）.Establish the upper extremity peripheral vein when arriving the operating room.Parturients were monitored electrocardiogram,blood pressure,oxygen saturation.BP and HR was measured every minute.Baseline SBP,DBP and HR were calculated as the mean of the three recordings.Parturients were placed in the right lateral position.The L3⁴interspace were selected for puncture of CSEA.After the success of the puncture,hyperbaric 0.5% bupivacaine were injected intrathecally（administration dose were based on the Harten doses chart）,with the speed of 0.2 m L/s.When the injection was completed,the needle was excluded.A catheter was placed into the epidural space toward the head 3 cm and supine position was restored.Then regulate the surgical bed at the position of 15 degrees to the left.Parturients were inhalansed oxygen with face mask at the flow rate of 4 L/min continuously during operation.At the time of intrathecal injection,NE were infused using a syringe pump at the speed of0.03 μg.kg^-1.min^-1,0.04 μg.kg^-1.min^-1,0.05 μg.kg^-1.min^-1 in the group N₁,N₂ and N₃,whereas group C recived nothing.Blood pressure was measured every minute after the spinal injection,then every 5 minutes after the delivery of the baby.When the systolic blood pressure（SBP）was decreased by more than 20% of the baseline value in the control group or experimental group,bolus injection of NE 8 μg was adopted intermittently.Hypertensive episodes（SBP >120% of baseline）were treated with infusion cessation in the experimental group,and the infusion was restarted when SBP decreased below the upper limit of the target range（120% of baseline SBP value）.Bradycardia（HR <60 beats/min）was a rescue bolus of atropine 0.3 mg.Firstly recorded the basic（T₀）SBP,DBP and HR.Then the SBP,DBP and HR were monitored and recorded 5 min（T₁）,10 min（T₂）,15 min（T₃）after spinal anesthesia,5 min after the neonate was born（T₄）,at the end of the surgery（T₅）.The PH value,PO₂,PCO₂,base excess（BE）of neonatal cord blood were detected immediately after neonate was born.The Apgar scores were recorded at the 1 min and 5 min time point after born.At the end of the operation,the incidences of hypotension,hypertension,nausea and vomiting,bradycardia of the parturients were recorded.The usage of NE of each parturient was recorded.Results:1、The incidence of hypotension（SBP decreased more than 20% of the baseline）in the control group（group C）was higher than that in group N₁（P< 0.05）and group N₂,N₃（P< 0.01）;the incidence of hypotension in group N₁ was higher than that in group N₂（P< 0.05）and group N₃（P< 0.01）when compared between experimental groups.2、The incidence of hypertension（SBP increased more than 20% of the baseline）in group N₃ was higher than that in the other three groups（P<0.01）.3、The incidence of nausea and vomiting in group C were higher than that in group N₁,N₂,N₃（P< 0.01）;there was no significant difference between N₁,N₂,and N₃ groups（P> 0.05）.4、The incidence of bradycardia in group C was higher than that in group N₁,N₂,N₃（P< 0.05）;there were no bradycardia occurred in group N₁,N₂,N₃.5、The total dosage of NE used in experimental groups were higher than that in group C（P< 0.01）;when compared between experimental groups,total dosage of NE used in group N₁ was less than that in group N₂（P< 0.05）and N₃（P< 0.01）;total dosage of NE used in group N₂ was less than that in group N₃（P< 0.05）.The maximum number of additional injection of NE is group C,followed by group N₁.6、SBP and DBP were higher in group N₂（P< 0.05）and group N₃（P<0.01）at T₁^T₄ time point than that of group C;when compared between experimental groups,the SBP and DBP in group N₁ were lower than that of group N₂（P< 0.05）at T₁^T₄ time points,the SBP and DBP in group N₃ were higher than that of group N₂（P< 0.05）at T₁^T₄ time points,the SBP and DBP in group N₁ were lower than that of group N₃（P< 0.01）at T₁^T₄ time points;HR was lower than other three groups（P< 0.05）at the time point of T₁^T₄ in group N₃;when compared in groups,the SBP and DBP of group C and group N₁ were lower at T₁^T₄ time points than that of T₀（P< 0.05）;the SBP and DBP of Group N₃ were higher at T₁^T₄ time point,and the HR was lower at T₁^T₄ time point than that of T₀（P< 0.05）.7、There were no significant difference in PH,PO₂,PCO₂ and BE of fetal umbilical artery blood between the four groups（P> 0.05）.8、There was no significant difference of the Apgar scores at the time of 1 min and 5 min after the neonate was born（P> 0.05）.Conclusion:The infusion of NE during cesarean delivery after CSEA has efficacy for maintaining hemodynamic stability and decreased the incidences of nausea and vomiting compare to the rescue bolus of NE and has no adverse effect on the fetus.The infusion rate of 0.04 μg.kg^-1.min^-1 of NE was suitable.