Beta-adrenoceptor agonists and hypoxia in sheep fetuses.
Sheep fetuses, near term, were studied to test the influence of a tocolytic beta agonist, terbutaline, on fetal responses to hypoxia. After fetal exteriorization the drug was administered intravenously to the mother in three different doses: The max group comprised 11 ewes receiving 67-134 micrograms min-1. Seven ewes were given 30 micrograms min-1 and eight ewes were infused with 10 micrograms min-1. Seventeen fetuses served as controls. Hypoxia was induced by intermittent complete occlusions of the maternal abdominal aorta. Maternal terbutaline levels were high (range 50-748 nmol l-1) in the max group and the 30-micrograms group, whereas those in the 10-micrograms group were in the clinical range (range 11-58 nmol l-1). Fetuses in the max and 30-micrograms groups reacted to moderate hypoxia with excessive responses of heart rate, blood pressure myocardial contractility and ST waveform changes and a 50% mortality rate during severe hypoxia as compared with 12% in the control animals. Ten micrograms min-1 did not decrease the survival but caused an increase in myocardial workload and a negative energy balance during severe hypoxia.
Dagbjartsson
A
A
Department of Pediatrics, Landspitalinn University Hospital, Reykjavik, Iceland.
Herbertsson
G
G
Stefansson
T S
TS
Kjeld
M
M
Lagercrantz
H
H
Rosen
K G
KG
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D005311:Fetal Hypoxia / Q000097:blood / Q000188:drug therapy / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects; D011247:Pregnancy; D011379:Prognosis; D012756:Sheep; D013726:Terbutaline / Q000008:administration & dosage*; D015145:Tocolysis
D013726:Terbutaline