Effects of continuous infusion of phenylephrine vs. norepinephrine on parturients and fetuses under LiDCOrapid monitoring: a randomized, double-blind, placebo-controlled study

Background: Hypotension following spinal anesthesia (SA) during cesarean delivery (CD) occurs commonly and is related with maternal and fetal complications. Norepinephrine infusion is increasingly used for prevention of post-SA hypotension; however, its effects as compared to the traditional phenylephrine infusion remain unclear. This study aimed to compare the effects of phenylephrine and norepinephrine administered as continuous infusion during elective CD on maternal hemodynamic parameters and maternal and fetal outcomes.

Methods: This prospective, single-center, randomized, controlled study included 238 consecutive term parturients who underwent CD from February 2019 to October 2019. They were randomized to receive continuous infusion of 0.25 μg/kg/min phenylephrine, 0.05 μg/kg/min norepinephrine, or placebo. Hemodynamic monitoring was performed at 10 time points using LiDCOrapid. We analyzed umbilical vein (UV), umbilical artery (UA), and peripheral vein (PV) blood gas indexes and recorded intraoperative complications.

Results: In phenylephrine group, the systolic blood pressure (SBP) remain during the whole operation. Compared to the control group, phenylephrine, but not norepinephrine, significantly increased the systemic vascular resistance (SVR) to counteract the SA-induced vasodilatation, 3 min following norepinephrine/phenylephrine/LR administration (T4): 957.4 ± 590.3 vs 590.1 ± 273.7 (P < 0.000001); 5 min following norepinephrine/phenylephrine/LR administration (T5): 1104 ± 468.0 vs 789.4 ± 376.2 (P = 0.000002). at the time of incision (T6): 1084 ± 524.8 vs 825.2 ± 428.6 (P = 0.000188). Parturients in the phenylephrine group had significantly lower UV (1.91 ± 0.43) (P = 0.0003) and UA (2.05 ± 0.61) (P = 0.0038) lactate level compared to controls. Moreover, the UV pH value was higher in the phenylephrine than in the control group7.37 ± 0.03(P = 0.0013). Parturients had lower incidence of nausea, tachycardia, hypotension in phenylephrine group.

Conclusions: In this dataset, continuous phenylephrine infusion reduced the incidence of SA-induced hypotension, ameliorated SVR, while decreasing overall maternal complications. Phenylephrine infusions are considered the better choice during CD because of the significant benefit to the fetus.

Trial registration: Clinicaltrial.gov Registry, NCT03833895 , Registered on 1 February 2019.

Keywords: Cesarean delivery; In-term parturient; LiDCOrapid system; Norepinephrine; Phenylephrine; Spinal anesthesia.