Hemodynamic effects of intravenous isoproterenol versus saline in the parturient.

The use of epinephrine as a test dose for epidural analgesia in obstetrics remains controversial. Isoproterenol as a test dose may be efficacious in the parturient. However, the effects of isoproterenol on the uterine blood flow (UBF) and umbilical blood flow (UMB) in the parturient are unknown. In a randomized, double-blind study, the hemodynamic variables in 60 nonlaboring women at term were studied 5 min before and for 10 min after an intravenous injection of either 5 micrograms isoproterenol or 5 micrograms saline. The UBF was assessed in 35 women and the UMB in 25 women using a color Doppler technique. The results of 50 women were used for further analysis. Maternal heart rate (MHR) was measured continuously, and maternal mean arterial pressure was measured every minute. MHR did not change after saline but increased significantly after injection of isoproterenol. UBF also increased significantly after isoproterenol during the same time interval. UMB did not change. Other hemodynamic variables did not change. We conclude that isoproterenol, 5 micrograms, may be a suitable test dose for epidural analgesia in obstetrics.