Fatima Khatoon et al.
Anesthesia & Analgesia, July 2025
Norepinephrine is approximately 13 times more potent than phenylephrine when used as a prophylactic infusion to prevent hypotension after spinal anesthesia for cesarean delivery. In this randomized, triple-blinded study of 60 patients, the authors determined the ED50 of norepinephrine to be 1.01 µg/min and that of phenylephrine to be 12.7 µg/min, establishing a potency ratio of 12.6:1. Both vasopressors were equally effective in maintaining systolic blood pressure within 20% of baseline. Hemodynamic variables such as cardiac output and heart rate showed no significant differences between groups when the infusion was effective. Based on these findings, the authors recommend initiating norepinephrine infusion at 1.9 to 3.8 µg/min as a safe and effective alternative to phenylephrine in managing spinal-induced hypotension during cesarean delivery.
KEY POINTS
Question: What is the optimal infusion rate of norepinephrine for prevention of hypotension after spinal anesthesia for cesarean delivery?
Findings: A relative potency ratio of norepinephrine: phenylephrine is 12.6 (95% confidence interval [CI], 9.92–15.9) when administered as an infusion and the median effective dose (ED50) of norepinephrine is 1.01 µg.min−1.
Meaning: Norepinephrine infusion initiated at a rate of 1.9 to 3.8 µg.min−1 can serve as a safe alternative to phenylephrine for prevention of hypotension after spinal anesthesia for cesarean delivery.
Reference:
Khatoon F, Kocarev M, Fernando R, Naz A, Khalid F, Abdalla EO, Columb M. Anesthesia & Analgesia. 2025 Jul;141(1):17-25. doi:10.1213/ANE.0000000000007231
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