Effects of intravenous infusions of noradrenaline into the pregnant ewe on uterine blood flow, fetal renal function, and lung liquid flow.
To determine the effects on the fetus of high maternal levels of noradrenaline, experiments were carried out in 17 pregnant ewes (123-137 days gestation). Intravenous infusion of 40 mg/min of norepinephrine to the ewe for 1.5 h increased maternal arterial pressure and significantly decreased maternal placental blood flow (p < 0.05). Fetal arterial pressure did not change, but fetal arterial PO2 fell (p < 0.01) and PCO2 rose (p < 0.01). Fetal urine flow fell and osmolality rose (p < 0.01), fetal lung liquid flow and osmolar excretion fell (p < 0.01, p < 0.05, respectively), and the lung sodium:potassium ratio changed. These effects of high levels of maternal noradrenaline were transient, i.e., 2.5 h after the infusion of noradrenaline had finished, fetal urine flow and lung liquid flow had both returned to control values and fetal PCO2 was significantly depressed relative to control values (p < 0.01). It is concluded that high levels of maternal catecholamines reduce placental blood flow and cause small changes in fetal oxygenation. These changes are sufficient to transiently affect fetal water excretion and to reduce lung liquid flow.
Stevens
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School of Physiology and Pharmacology, University of New South Wales, Kensington, Australia.
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D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D005312:Fetal Blood / Q000187:drug effects / Q000378:metabolism; D005333:Fetus / Q000187:drug effects; D007275:Injections, Intravenous; D007668:Kidney / Q000187:drug effects*; D008168:Lung / Q000187:drug effects*; D008431:Maternal-Fetal Exchange; D009638:Norepinephrine / Q000494:pharmacology*; D021041:Placental Circulation / Q000187:drug effects; D011247:Pregnancy; D012756:Sheep; D014599:Uterus / Q000098:blood supply / Q000187:drug effects*
D002245:Carbon Dioxide; D009638:Norepinephrine