ED95 determination of continuous norepinephrine infusion for preventing spinal anesthesia-induced hypotension in obese parturients during cesarean delivery

Abstract

Background Norepinephrine is an effective vasopressor for preventing and managing spinal anesthesia-induced hypotension during cesarean delivery. Nevertheless, data regarding the 95% effective dose (ED95) of continuous norepinephrine infusion in obese parturients remain scarce. Methods This prospective dose-finding study enrolled parturients scheduled for elective cesarean delivery under spinal anesthesia. Participants were stratified into two groups based on body mass index (BMI): non-obese group (BMI <30 kg/m2) and obese group (BMI ≥30 kg/m2). Intravenous norepinephrine infusion was initiated at a dose of 0.01 μg/kg/min in the first participant, with subsequent dosages adjusted according to the preceding patient’s response using a biased coin design up-and-down sequential method. Spinal anesthesia-induced hypotension was defined as a mean arterial pressure of below 65 mmHg sustained for more than 1 minute within 30 min following intrathecal injection. The 95% effective dose (ED95) was estimated via isotonic regression coupled with bias-corrected bootstrapping. Maternal and neonatal outcomes, including adverse events, were recorded. Results Eighty parturients were included in the analysis. The ED95 of norepinephrine was determined to be 0.045 μg/kg/min (95% confidence interval [CI], 0.03–0.05 μg/kg/min) in the non-obese group and 0.0662 μg/kg/min (95% CI, 0.055–0.075 μg/kg/min) in the obese group. No significant differences were observed in maternal or neonatal outcomes between the two cohorts. Conclusion The findings indicate that obese parturients require a significantly higher prophylactic dose of norepinephrine infusion to prevent spinal anesthesia-induced hypotension compared to the non-obese counterparts. These results underscore the importance of individualized dosing strategies based on BMI to optimize hemodynamic management in obese parturients undergoing cesarean delivery.