The Effect of Ephedrine upon Uterine Artery Blood Flow Velocity in the Pregnant Guinea Pig Subjected to Terbutaline Infusion and Acute Hemorrhage

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Abstract
The purpose of the present study was to determine the effect of intravenously administered ephedrine upon uterine artery blood flow velocity (UBFV) in the gravid guinea pig subjected to terbutaline infusion and acute hemorrhage. Ephedrine, 1.0 mg/kg, was administered intravenously to ten chronically instrumented pregnant guinea pigs near term, before and after intravenous infusion of terbutaline and acute hemorrhage. Before terbutaline and hemorrahge, ephedrine increased maternal mean arterial pressure (MMAP) by 30 .+-. 1% (P = 0.0001) and 17 .+-. 1% (P = 0.0001) at 30 s and at 1 min after injection, respectively; UBFV was decreased by 10 .+-. 4% (P < 0.01) and 14 .+-. 4% (P < 0.01) at 1 min and at 90 s after injection, respectively. Infusion of terbutaline (1.5-6.0 .mu.g .cntdot. kg-1 .cntdot. min-1) increased maternal heart rate (MHR) by 22 .+-. 1% (P = 0.0001), decreased MMAP by 13 .+-. 2% (P = 0.001), and decreased UBFV by 24 .+-. 3% (P = 0.001). During hypotension resulting from acute hemorrhage, ephedrine, 1.0 mg/kg, was superior to placebo in restoring MMAP and UBFV toward the prebleed values. The authors concluded that ephedrine, 1.0 mg/kg, results in a small, transient decrease in UBFV in the normotensive gravid guinea pig. However, ephedrine aids restoration of UBFV in the gravid guinea pig rendered hypotensive by acute hemorrhage during terbutaline infusion.

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