Comparison of intermittent boluses of noradrenaline vs. phenylephrine for spinal anesthesia induced hypotension during cesarean delivery

Background and Objective: Maternal hypotension is a common consequence of spinal anesthesia for cesarean delivery (CD). A vasopressor is recommended in addition to adequate fluid loading to raise mean arterial pressure in pregnant women. Phenylephrine, a pure α–adrenergic receptor agonist, is the first-line agent to manage it. However, phenylephrine is associated with dose-dependent reflex bradycardia and decreased cardiac output. Noradrenaline is suggested as an alternative due to its mild beta-adrenergic effect, which results in a greater heart rate and cardiac output than phenylephrine. We compared the effectiveness and adverse effects of intermittent boluses of noradrenaline with phenylephrine to treat spinal-induced hypotension during CD. Methodology: A randomized controlled trial was conducted at Bach Mai Hospital, Vietnam, from May 2020 to August 2020. There were 120 pregnant women undergoing elective CD under spinal anesthesia enrolled in the study and divided randomly into two groups: the Group N and the Group P. Group N patients were given noradrenaline 6 µg as an intravenous bolus, and Group P patients were given phenylephrine 100 µg to treat spinal-induced hypotension. The primary outcome was the number of bolus doses of vasopressors needed to treat maternal hypotension. Secondary outcomes were bradycardia, hypertension, nausea, vomiting, umbilical arterial blood gases, and APGAR scores. Results: The number of boluses of vasopressors needed to treat hypotension and maternal hemodynamic changes was equivalent in both groups. The incidence of bradycardia, nausea, and vomiting in the two groups was not significantly different. No pregnant woman suffered from unintended hypertension. APGAR scores were 7 and above at one min and 10 and above at five min for all cases. There were no differences in umbilical arterial pH values between the two groups (7.33 vs. 7.34; P > 0.05). Conclusion: Noradrenaline 6 µg and phenylephrine 100 µg boluses were equally effective in treating spinal-induced hypotension in parturients undergoing cesarean delivery with similar neonatal and maternal outcomes. Abbreviations: CD - Cesarean Delivery; HR - Heart Rate; CO - Cardiac Output; SVR - Systemic Vascular Resistance; SBP - Systolic Blood Pressure; ED 90 - 90 Percent Effective Dose Key words: Anesthesia, Spinal; Hypotension; Cesarean Delivery Citation: Nguyen TT, Nguyen HC, Nguyen ATH, Doan TH, Ngo QS. Comparison of intermittent boluses of noradrenaline vs. phenylephrine for spinal anesthesia induced hypotension during cesarean delivery. Anaesth. pain intensive care 2023;27(5):562−566. DOI: 10.35975/apic.v27i5.2312 Received: August 22, 2023; Reviewed: August 23, 2023; Accepted: August 31, 2023