Comparison of the Vasoconstriction Effect of Phenylephrine and Ephedrine on the Uterine Arteries of Pregnant Rabbits: A CT Imaging-Based Study

Abstract Background: Hypotension is one of the most common complications during perioperative obstetric surgery and can cause serious adverse reactions in mothers and infants. Phenylephrine and ephedrine are the most widely used vasoconstrictors for preventing and controlling hypotension. However, which of them is the best choice remains unclear due to the lack of solid data on the effects of phenylephrine and ephedrine on uterine placental blood flow. This study aims to investigate the vasoconstriction effect of phenylephrine and ephedrine on the uterine arteries of pregnant rabbits via computed tomography (CT) imaging.Methods: Fifteen near-term pregnant rabbits at 27-29 days of pregnancy were randomly divided into Group P, Group E and Group C. Phenylephrine, ephedrine and normal saline were injected. CT imaging was performed, and the diameters of the uterine arteries were measured to evaluate the contractile response to different drugs.Results: Both phenylephrine and ephedrine induced a similar degree of vasoconstriction on peripheral resistance of the vessels (rostral arteries) (p>0.05). At 5 min and 10 min, the uterine arteries contracted more strongly in response to phenylephrine than ephedrine (p<0.01); after that, there was no significant difference in the diameters of the uterine arteries with the administration of phenylephrine and ephedrine (p>0.05).Conclusion: In summary, compared with ephedrine, phenylephrine had a faster effect, and resulted in stronger contraction of the uterine arteries, indicating a greater impact on placental perfusion. Therefore, in clinical practice, ephedrine has more favorable effects than phenylephrine on uterine and placental circulation.