Epinephrine does not alter human intervillous blood flow during epidural anesthesia.

The effect of epinephrine given epidurally with local anesthetics on uterine blood flow is controversial. Previous work in pregnant ewes demonstrated a transient but significant (14 per cent) decrease in uterine blood flow when 2-chloroprocaine with epinephrine (10 micrograms/l) was used. The authors administered 2-chloroprocaine, 10 ml, with epinephrine (5 micrograms/ml) to 12 healthy women during the first stage of labor. By use of intravenously injected 133Xe, intervillous blood flow was measured before and 15-20 min after epidural anesthesia to a somatic level of at least T10. Intervillous blood flow did not change significantly despite a decrease in mean blood pressure of 11 torr. These conflicting results are probably best explained by methodologic and species differences. It is postulated that human placental vasculature, unlike that of the ewe, undergoes vasodilation when perfusion pressure is decreased to maintain placental blood flow.