A randomised double-blind comparison of phenylephrine and norepinephrine for the management of postspinal hypotension in pre-eclamptic patients undergoing caesarean section

BACKGROUND: Studies comparing phenylephrine and norepinephrine for the treatment of postspinal hypotension in pre-eclamptic patients are limited. OBJECTIVE: To compare bolus doses of phenylephrine and norepinephrine for treating hypotension in pre-eclamptic mothers undergoing caesarean section under spinal anaesthesia. It was hypothesised that norepinephrine and phenylephrine use would be associated with similar neonatal outcome. DESIGN: Randomised controlled study. SETTING: Single centre, tertiary care, university teaching hospital, from December 2018 to March 2020. PATIENTS: A total of 86 women with pre-eclampsia and a singleton pregnancy who developed postspinal hypotension during caesarean section. INTERVENTIONS: Patients received intravenous phenylephrine (50 μg) or norepinephrine (4 μg) for treatment of hypotension, defined as a fall in baseline systolic BP by ≥ 20% or an absolute value < 100 mmHg. MAIN OUTCOME MEASURES: The primary outcome was umbilical artery pH. Secondary outcomes included Apgar scores, the number of hypotensive episodes, vasopressor requirements, the incidence of tachycardia/bradycardia/arrhythmias/hypertension and maternal complications. RESULTS: Umbilical artery pH was not different between the phenylephrine and norepinephrine groups (7.26 ± 0.06 and 7.27 ± 0.06, respectively; P = 0.903). The median [IQR] number of hypotensive episodes was higher in the norepinephrine than the phenylephrine group: 2 [1 to 3] vs 1 [1 to 2], respectively; P = 0.014. Apgar scores, total number of vasopressor boluses required, systolic BP trends and the incidence of maternal complications were comparable in the two groups. Heart rate (HR) values were lower in phenylephrine group (P = 0.026), and one patient in phenylephrine group and none in the norepinephrine group developed bradycardia (HR < 50 bpm), P = 1.000. CONCLUSIONS: In women with pre-eclampsia undergoing caesarean section, bolus doses of phenylephrine (50 μg) and norepinephrine (4 μg) used to treat hypotension after spinal anaesthesia are equally effective with similar neonatal and maternal outcomes. TRIAL REGISTRATION: CTRI/2018/11/016478.