Norepinephrine Infusion for Preventing Postspinal Anesthesia Hypotension during Cesarean Delivery: A Randomized Dose-finding Trial.

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(-1) dose 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(-1) norepinephrine infusion rates effectively reduced postspinal hypotension during cesarean delivery compared with the 0.025-μg · kg(-1) · min(-1) infusion rate.