Comparison of prophylactic phenylephrine and norepinephrine infusion on umbilical arterial pH and maternal blood pressure during spinal anaesthesia for caesarean delivery.

Background And Aims: Spinal anaesthesia induced maternal hypotension in parturients undergoing caesarean delivery may lead to neonatal acidosis and fall in umbilical artery pH. The aim of this study was to compare low dose norepinephrine infusion with phenylephrine to see the effect on umbilical arterial pH and maternal blood pressure during spinal anaesthesia for caesarean delivery.

Methods: In a randomised, double-blind study, 60 parturients belonging to American Society of Anesthesiologists grade II, age 18-35 years with singleton term pregnancy were divided into the phenylephrine group and norepinephrine group. Participants received prophylactic phenylephrine and norepinephrine infusion after spinal anaesthesia till the delivery of the baby at a fixed rate of 50 μg/min and 2.5 μg/min, respectively. The primary outcome was umbilical artery pH. Neonatal Apgar score, incidence of bradycardia and hypotension, number of boluses of vasopressor required and reactive hypertension were also compared.

Results: The umbilical arterial pH was comparable between the groups (p = 0.38). Apgar scores were comparable (p = 0.17). Incidence of bradycardia was higher in phenylephrine group without reaching statistical significance (43.3% vs. 20%, = 0.052). Incidence of hypotension was more but not significant in norepinephrine group compared to phenylephrine group (16.7% vs. 10%, = 0.44). Number of vasopressor boluses and reactive hypertension episodes were comparable between both groups (p = 0.09).

Conclusion: Low dose (2.5 μg/min) intravenous infusion of norepinephrine is a suitable alternative to phenylephrine in the maintenance of umbilical arterial pH and maternal blood pressure.