Studies on Ductus Arteriosus Circulation.

نویسندگان

N S ASSALI

J A MORRIS

R W SMITH

W A MANSON

چکیده

• Two principal mechanisms have been proposed to explain closure of the ductus arteriosus. Bareroft et al.2 thought that functional closure of this vessel occurred shortly after clamping the umbilical cord and that the stimulus for closure was neurogenic. Kennedy and Clark' failed to find a neurogenie mechanism and suggested that closure was related to increased oxygenation of the bJood following the onset of breathing. Barron" tested this hypothesis by injecting 100 ml of oxygenated blood in the jugular vein of a lamb but noted no effect on the duetus. Dawes and his co-workers,' however, in a series of systematic studies carried out in the fetal lamb observed that inflation of the lungs with oxygen led to constriction of the dnctus and to production of a murmur over it. This murmur was attributed to passage of blood through the narrowed lumen of the ductus. Ventilation of the lungs with nitrogen had no such effect. They concluded that these changes were due to a specific vasoconstrictive effect of oxygen upon the ductus. Tet these same investigators reported similar constriction of the ductug in fetal lambs with hyposia and asphyxia. They suggested that, in these circumstances, the constriction might have been due to excessive secretion of catechol amines stimulated by the hypoxda and the asphyxia. Although the studies of Dawes and his associates provided valuable information re-

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