Dose–Response Study of 4 Weight-Based Phenylephrine Infusion Regimens for Preventing Hypotension During Cesarean Delivery Under Combined Spinal–Epidural Anesthesia

BACKGROUND:Prophylactic IV infusion of phenylephrine has been recommended to prevent hypotension during spinal anesthesia for cesarean delivery. However, the optimal infusion dose is unknown. This study aimed to determine the infusion dose of phenylephrine that would be effective in preventing hypotension in 50% (ED50) and 90% (ED90) of patients when administered as a prophylactic infusion at a fixed rate based on the individual body weight. METHODS:Eighty parturients scheduled for elective cesarean delivery were randomly allocated to receive IV infusion of prophylactic phenylephrine at 0.25, 0.375, 0.5, or 0.625 µg/kg/min (n = 20 per group) started immediately after intrathecal injection of 10 mg hyperbaric bupivacaine and 5 µg sufentanil using a combined spinal–epidural technique. An effective dose was defined by the occurrence of no hypotension (defined as a decrease in systolic blood pressure by ≥20% below baseline and to