Maternal And Neonatal Effects Of Three Different Administration Regimens Of Phenylephrine For Treating Hypotension After Spinal Anesthesia For Caesarean Section:a Randomized Controlled Trial

Objective:To observe the effects of three different administration regimens of phenylephrine on parturient and neonate during spinal anesthesia for cesarean section.Methods : One hundred and twenty singleton gestation parturients scheduled for elective cesarean section undcr spinal anesthesia were randomly divided into three groups.group A（n=40）: normal saline 5ml,group B（n=40）:an intravenous bolus of phenylephrine 100μg,group C（n=40）: phenylephrine infusion at 25μg/min,intravenously injected immediately after the injection of the intrathecal medication.The parturients in the three groups received hydroxyethyl starch 10ml/kg before spinal anesthesia.Hypotension,defined as an SBP <80% of baseline SBP for 2 consecutive readings,was treated with a bolus of phenylephrine 50μg.bradycardia,defined as an HR <60bpm,was treated with atropine 0.25 mg.SBP and HR were recorded at every minutes until 20 min after spinal anesthesia.No.of patients receiving a phenylephrine and atropine bolus,times of phenylephrine and atropine interventions and total phenylephrine dose were recorded from intrathecal injection to delivery.No.of reactive hypertension and bradycardia episodes were recorded from intrathecal injection to delivery.Apgar scores and umbilical cord blood gases were recorded.Results:In group C,SBP and HR were more stable than group A and group B for ten minutes after intrathecal injection.SBP in group A decreased to the lowest at 4min,significant differences compared wih T₀（P<0.05）,SBP in group B increased to the highest at 3min,decreased to the lowest at 7 min,significant differences compared wih T₀（P<0.05）;HR in group A increased to the highest at 3min,significant differences compared wih T₀（P <0.05）.Group C were associated with significantly fewer interventions than group A and B（P<0.05）.total phenylephrine dose in group C were higher compared with group A and B（P<0.05）.The incidence of chest tightness and nausea in group C were lower than group A（P<0.05）.No vomiting occurred in the three groups.There were no significant differences in reactive hypertension among groups.There were no significant differences in umbilical cord gases or in 1-and 5-minute Apgar scores among groups.Conclusion : Three administration regimens of phenylephrine can correct hypotension after spinal anesthesia for elective cesarean section,and no adverse effects on the newborn.prophylactic phenylephrine infusions were associated with greater maternal hemodynamic stability with minor adverse effects compared with group A and B,and no adverse effects on the newborn.