Hypotension after spinal anesthesia for cesarean delivery is common, usually treated with phenylephrine or ephedrine
Norepinephrine was recently introduced in obstetric anesthesia but the optimal dose is unknown
What This Article Tells Us That Is New:
This randomized, double-blinded trial compared prophylactic norepinephrine infusions of 0.025, 0.050, or 0.075 µg · kg-1 · min-1, started after bupivacaine spinal anesthesia, in full-term parturients having elective cesarean delivery
The primary outcome, maternal hypotension (systolic blood pressure less than 80% of baseline), occurred less frequently after both 0.050 and 0.075 µg · kg-1 · min-1compared 0.025 µg · kg-1 · min-1 norepinephrine
Background: Norepinephrine has been recently introduced for prophylaxis against postspinal hypotension during cesarean delivery; however, no data are available regarding its optimum dose. The objective of this study is to compare three infusion rates of norepinephrine for prophylaxis against postspinal hypotension during cesarean delivery.
Methods: The authors conducted a double-blinded, randomized, controlled study including full-term pregnant women scheduled for cesarean delivery. Norepinephrine infusion was commenced after subarachnoid block. Patients were randomized into three groups, which received norepinephrine with starting infusion rates of 0.025 µg · kg-1 · min-1, 0.050 µg · kg-1 · min-1, and 0.075 µg · kg-1 · min-1. Infusion was stopped when intraoperative hypertension occurred. The primary outcome was the frequency of postspinal hypotension (defined as decreased systolic blood pressure less than 80% of the baseline reading). The three groups were compared according to the following: systolic blood pressure, heart rate, frequency of intraoperative hypertension, frequency of bradycardia, and neonatal outcomes.
Results: Two hundred eighty-four mothers were included in the analysis. The frequency of postspinal hypotension was lower for both the 0.050-µg · kg-1 · min-1dose group (23/93 [24.7%], odds ratio: 0.45 [95% CI: 0.24 to 0.82], P = 0.014) and the 0.075-µg · kg-1 · min-1 dose group (25/96 [26.0%], odds ratio: 0.48 [95% CI:0.26 to 0.89], P = 0.022) compared with the 0.025-µg · kg-1 · min-1 dose group (40/95 [42.1%]). The two higher-dose groups (the 0.050-µg · kg-1 · min-1 group and the 0.075-µg · kg-1 · min-1 group) had higher systolic blood pressure and lower heart rate compared with the 0.025 µg · kg-1 · min-1 group. The three groups were comparable in the frequency of intraoperative hypertension, incidence of bradycardia, and neonatal outcomes.
Conclusions: Both the 0.050-µg · kg-1 · min-1 and 0.075-µg · kg-1 · min-1norepinephrine infusion rates effectively reduced postspinal hypotension during cesarean delivery compared with the 0.025-µg · kg-1 · min-1 infusion rate.