Post-spinal hypotension management for cesarean section in low resource settings: efficiency and safety of two very low-dose boluses of norepinephrine, a randomized double-blinded controlled trial

Spinal anesthesia is the gold standard anesthetic technique for cesarean section. However, its major complication is hypotension. Norepinephrine has recently been described as an efficient and safe alternative to Phenylephrine. The aim of this study was to determine the effective target bolus of Norepinephrine to prevent and treat post-spinal anesthesia hypotension. We conducted a prospective controlled randomized study including 126 parturients scheduled for cesarean delivery under spinal anesthesia. We compared two groups that received a prophylactic bolus of either 1μg/kg or 0.5μg/kg of Norepinephrine without fluid loading. The rescue intravenous bolus of Norepinephrine was half the dose of the prophylactic bolus. The main outcomes were the percentage of decrease in systolic and mean blood pressure. The secondary outcomes included the timing of the first hypotension, duration of hypotension, number of rescue boluses, total Norepinephrine consumption, incidence of hypotension and maternal adverse effects and fetal outcomes. Our primary outcome has shown similarities between groups; delta systolic blood pressure before delivery was 19.4% in group 1µg/kg versus 20.5% in group 0.5µg/kg. Both groups were similar for all secondary outcomes, except that the higher dose of Norepinephrine resulted in more hypertension. Fetal outcomes were similar in both groups. Bolus of 0.5μg/kg followed by rescue doses of 0.25μg/kg of Norepinephrine was efficient in preventing and treating spinal anesthesia-induced hypotension. These doses may be recommended for routine use in healthy parturients.