Determining the ED90 of prophylactic phenylephrine and norepinephrine infusions for higher blood pressure target maintenance during cesarean delivery: a randomized sequential allocation trial.

BACKGROUND

The international consensus on vasopressors for managing hypotension emphasizes maintaining maternal systolic blood pressure (SBP) during cesarean delivery greater than 90% of the baseline and not below 80%. This study was to determine the ED90 values of prophylactic norepinephrine and phenylephrine infusions under higher blood pressure management target of maintaining maternal SBP at greater than 90% of the baseline.

METHOD: Sixty patients aged 18-45 years, who were scheduled to undergo cesarean delivery under spinal anesthesia, were randomly assigned to the norepinephrine group and the phenylephrine group. The first patients in each group were administered prophylactic infusion rates of 0.05 and 0.5 μg/kg/min, respectively. Effectiveness was determined based on whether the current vasopressor infusion dose could achieve the predefined target for maternal SBP management at greater than 90% of the baseline prior to fetal delivery. Subsequently, the vasopressor infusion rate was adjusted incrementally or decrementally by 0.01 and 0.1 μg/kg/min as needed. Additionally, maternal adverse events and neonatal outcomes were systematically recorded and analyzed.

RESULTS

Through isotonic regression analysis, the ED90 values for prophylactic norepinephrine and phenylephrine infusions under a higher blood pressure management target were estimated to be 0.140 μg/kg/min (95% CI: 0.133-0.147) and 1.280 μg/kg/min (95% CI: 1.180-1.380), respectively. There was no statistically significant difference in the incidence of adverse events or neonatal outcomes between groups.

CONCLUSION

When the target was established to maintain the blood pressure of patients at greater than 90% of the baseline prior to delivery in patients undergoing cesarean delivery, the prophylactic infusion rates for norepinephrine and phenylephrine were determined to be 0.140 and 1.280 μg/kg/min, respectively.

CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov, NCT06158048.