Prophylactic norepinephrine infusion for postspinal anesthesia hypotension in patients undergoing cesarean section: A randomized, controlled, dose-finding trial

Study Objective Prophylactic norepinephrine infusion effectively lowers the incidence of postspinal anesthesia hypotension. The optimal prophylactic dose of norepinephrine remains undefined. The purpose of this study was to investigate the optimal prophylactic dose of norepinephrine to prevent postspinal anesthesia hypotension in patients undergoing cesarean section. Design Prospective, double-blind, randomized, controlled, dose-finding trial. Setting Operating room from March 2020 to June 2020. Patients Ninety nine primipara or multipara women 18 - 40 years of age, singleton pregnancy >= 37 weeks, American Society of Anesthesiologists' physical status 1 or 2, scheduled for elective cesarean section under spinal anesthesia were included in this study. Intervention Patients were randomly assigned into groups to receive normal saline (NS) or one of four different prophylactic doses (0.025 [NE25], 0.05 [NE50], 0.075 [NE75], and 0.1 [NE100] ug/kg/min) of norepinephrine. The primary end point was the incidence of postspinal anesthesia hypotension (systolic blood pressure [SBP] < 80% of baseline) within 15 min after spinal anesthesia. Secondary outcomes included the overall stability of SBP control versus baseline (median performance error [MDPE] and median absolute performance error [MDAPE]), the dose that would be effective in preventing postspinal anesthesia hypotension in 50% (effective dose, ED 50) and 90% (ED90) of patients, other adverse events (bradycardia, nausea, vomiting, hypertension, and the total additional bolus of norepinephrine and atropine), and neonatal outcomes (blood gas values and Apgar scores). Measurements and Main Results The incidence of postspinal anesthesia hypotension in NS, NE25, NE50, NE75, and NE100 groups was 68.42% (13/19), 40.00% (8/20), 20.00% (4/20), 15.00% (3/20), and 10.00% (2/20), respectively. With increasing prophylactic doses of norepinephrine, the incidence of postspinal anesthesia hypotension decreased (p < 0.001), SBP was maintained closer to the baseline (MDPE, p < 0.001; MDAPE, p = 0.001), and the total additional bolus of norepinephrine decreased (p < 0.001). The ED50 and ED90 values of norepinephrine were 0.016 (95% CI: -0.014 - 0.033) and 0.088 (95% CI: 0.068 - 0.133) ug/kg/min, respectively. Other adverse effects, neonatal outcomes, and the total additional bolus of atropine did not differ among the five groups. Conclusions A prophylactic dose of 0.05 or 0.075 mu g/kg/min norepinephrine prevents postspinal anesthesia hypotension in patients undergoing cesarean section.

Automated summary

The study aimed to investigate the optimal prophylactic dose of norepinephrine to prevent postspinal anesthesia hypotension in cesarean section patients, with findings indicating that a prophylactic dose of 0.05 or 0.075 micrograms/kg/min effectively prevents postspinal anesthesia hypotension.