Determination of ED90s of Phenylephrine and Norepinephrine Infusion for Strict Blood Pressure Management Targets in Preeclamptic Patients Undergoing Cesarean Section: A Randomized Sequential Allocation Study.

Background: The consensus recommends maintaining the patient's systolic blood pressure at or above 90% of the baseline value, and highlights the use of vasopressors as the primary strategy for preventing and managing hypotension during cesarean section. This study was aimed to determine the ED90 of prophylactic infusions of norepinephrine and phenylephrine in preeclamptic patients under strict blood pressure management target (maintaining ≥90% of the baseline value). Methods: 60 preeclamptic patients were randomly assigned to either the norepinephrine or the phenylephrine group. The initial patients received an infusion of norepinephrine at 0.05 μg/kg/min or phenylephrine at 0.5 μg/kg/min. For subsequent patients, infusion rates were adjusted in increments or decrements of 0.01 or 0.1 μg/kg/min, respectively, to achieve strict blood pressure management targets before delivery. Secondary outcomes included patients' adverse events, umbilical artery blood gas analysis, and newborns' Apgar scores. Results: The isotonic regression analysis revealed that the ED90 values of norepinephrine and phenylephrine infusions required to maintain a strict blood pressure management targets were 0.076 μg/kg/min (95% CI, 0.070-0.080) and 0.900 μg/kg/min (95% CI, 0.850-0.950), respectively. The secondary outcomes between groups were comparable. Conclusion: Under strict blood pressure management target in preeclamptic patients undergoing cesarean section, the ED90 values for norepinephrine and phenylephrine infusions are 0.076 μg/kg/min and 0.900 μg/kg/min, respectively. Trial Registration: This study was registered at ClinicalTrials.gov on November 28, 2023 (No. NCT06158022).