Norepinephrine Prophylaxis for Postspinal Anesthesia Hypotension

Post-spinal anesthesia hypotension is a frequent complication during spinal anesthesia for cesarean section. The incidence of post-spinal anesthesia hypotension is as high as 62.1-89.7% if prophylactic measures are not taken. Vasopressors has been highly recommended for routine prevention and/or treatment of post-spinal anesthesia hypotension. As a potential substitute drug for phenylephrine, norepinephrine has gradually been used in parturients undergoing cesarean section. There's some evidence that prophylactic infusion of norepinephrine could effectively reduce the incidence of post-spinal anesthesia hypotension in parturients undergoing cesarean section. But the ideal infusion dose of norepinephrine is still unknown. The purpose of this study is to investigate the suitable infusion dose of norepinephrine for prophylaxis against post-spinal anesthesia hypotension.

Inclusion criteria

• 18-40 years
• Primipara or multipara
• Singleton pregnancy ≥37 weeks
• American Society of Anesthesiologists physical status classification I to II
• Scheduled for elective cesarean section under spinal anesthesia

Exclusion criteria

• Body height < 150 cm
• Body weight > 100 kg or body mass index (BMI) ≥ 40 kg/m2
• Eclampsia or chronic hypertension or baseline blood pressure ≥ 160mmHg
• Hemoglobin < 7g/dl
• Fetal distress, or known fetal developmental anomaly