Umbilical venous pressure and other cardiovascular responses of fetal lambs to epinephrine

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Abstract
Large fetuses in utero are more sensitive to infused epinephrine than smaller ones. The quality of response is the same. Increased arterial blood pressure and heart rate are associated with an increase in umbilical vein pressure. The large fetus is as sensitive as the pregnant ewe and the latter is more sensitive than the nonpregnant ewe. Single injections of epinephrine into umbilical or femoral veins have similar effects, except for the difference that the latent period is about twice as long when epinephrine is given by the femoral route as by the umbilical route. The sphincter of the ductus venosus is believed to constrict in response to epinephrine. It is shown to be adrenergically controlled. The import of the sphincter for maintenance of umbilical vein pressure is considered.