Influence of phenylephrine or ephedrine on maternal hemodynamics upon umbilical cord clamping during cesarean delivery.

BACKGROUND AND OBJECTIVE:Vasopressors ephedrine and phenylephrine are commonly used with spinal anesthesia during cesarean delivery. Studies on them have focused on the period before the umbilical cord is clamped, although anesthesia is continuously administered throughout and after this event. This study aimed to compare the effects of these drugs on maternal hemodynamics at and after clamping of the umbilical cord. STUDY DESIGN:Prospective, randomized, double-blind study. SETTING:Parturients (n = 60) scheduled for elective cesarean delivery were randomly divided into an ephedrine group and a phenylephrine group. Each woman received an intrathecal injection of bupivacaine (7.5 mg). MEASUREMENTS:Patients in the ephedrine and phenylephrine groups were infused continuously with ephedrine (0.02 mg×kg-1×min-1) or phenylephrine (0.25 μg×kg-1×min-1), respectively, from immediately after the injection of bupivacaine until termination 10 minutes after the umbilical cord was clamped (the endpoint). Hemodynamic changes were recorded. RESULTS:After clamping the umbilical cord, the patients who were administered ephedrine experienced significant increases in heart rate (89 ± 11 beats/min to 106 ± 15 beats/min), cardiac output (6.4 ± 0.9 l/min to 7.6 ± 1.2 l/min) and cardiac index (3.5 ± 0.39 l×min-1×m-2 to 4.3 ± 0.48 l×min-1×m-2), while the systemic vascular resistance decreased (908 ± 296 dyne·s/cm5 to 711 ± 285 dyne·s/cm5). Such differences were not observed in the patients who received phenylephrine. Moreover, the heart rate of patients administered ephedrine was higher than that of patients given phenylephrine after clamping the umbilical cord. CONCLUSION:Continuous infusion of phenylephrine during cesarean delivery maintains a stable maternal hemodynamic status better than ephedrine.