[Metabolic, cardiovascular and sympathoadrenal reactions of the fetus to progressive XXXX --animal experiment studies].

@entity1369 @entity742 @entity935 @entity26 @entity7396 @entity591 @entity519 @entity880 @entity2922 @entity701 @entity1063 @entity2661 @entity9734 @entity1168 @entity2241
During delivery a reduction of placental blood flow in relation to uterine contractions resulting in repetitive decelerations of the fetal heart rate is frequently encountered. In this context the question arises whether a critical threshold of @entity26 saturation ( @entity9734 ) in fetal arterial blood can be defined, below which a severe @entity2241 and a @entity2241 may develope. In chronically instrumented ewes (8 experiments) a slowly progressive @entity7396 was induced by stepwise reduction of uterine blood flow via occlusion of the maternal aorta. Fetal arterial blood pressure and heart rate were continuously monitored and fetal arterial blood samples were taken intermittently from a catheter placed in the fetal aorta. The stepwise decrease of fetal arterial @entity9734 was 10% at time intervals of 15-30 minutes. With @entity9734 -values above 15%, @entity880 increased 0.01-0.03 mmol/l/min and the pH decreased 0.003-0.0012/min. A significant increase of @entity880 concentration (0.1-0.3 mmol/l/min) and decrease of the pH (0.003-0.009/min) was encountered when the fetal arterial @entity9734 was below 15%. With progressive desoxygenation systolic and diastolic blood pressure as well as pulse pressure increased. There was no uniform reaction pattern of the basal fetal heart rate to progressive @entity519 ; while in some experiments @entity591 prevailed, @entity1168 was encountered in other experiments. Plasma free @entity2661 exhibited an inverse relationship to @entity9734 with an exponential increase of @entity2922 concentrations when @entity9734 fell below 15-20%. During almost complete desoxygenation ( @entity9734 below 5%), @entity2922 concentrations were increased 100 fold ( @entity1063 ), 1000 fold (epinephrine) and 50 fold ( @entity935 ) as compared to control values. In comparison to free @entity2661 increases of the concentrations of @entity701 and @entity1369 were only small. The increase of @entity701 with progressive @entity519 may explain the endogenous stimulation of lung maturity during fetal stress. Our experiments suggest that a @entity9734 level of 15-20% represents a critical threshold for development of severe @entity2241 and a @entity2241 . However, even during severe @entity519 ( @entity9734 below 10%) the @entity742 fetus is able to maintain blood pressure for at least 30 minutes with the help of an excessive @entity2922 secretion. Only with @entity519 a @entity2241 has to be anticipated within a few minutes.
