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Observations in the Fetal Lamb

J. E. McMullen, MD; C. F. Kittle, MD; R. M. Lauer, MD

Am J Dis Child. 1968;115(2):217-221.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

IN THE fetal lamb the pulmonary vascular resistance is higher than systemic vascular resistance so that most of the blood entering the pulmonary artery passes through the ductus arteriosus to the aorta.¹ The initial ventilation of the lungs results in a marked fall in pulmonary resistance and allows adequate perfusion of the lung for oxygenation.² The prompt fall in pulmonary resistance with a newborn lamb's first breath is thought to be the result of arteriolar vasodilation in response to an elevation of the PO₂ and fall of the Pco₂ in the alveolus.^3,4

The pulmonary vascular resistance in the fetal lamb can also be reduced by the exogenous administration of acetylcholine, isoproterenol, and histamine. Further, the stimulation of the vagi results in pulmonary vasodilation of the fetal lungs.⁵ Thoracic sympathectomy has also been shown to cause pulmonary vasodilation indicating the presence of sympathetic tone.⁵ . . . [Full Text PDF of this Article]

Author Affiliations
Kansas City, Kan

From the departments of pediatrics (Dr. Lauer), physiology and surgery (Drs. McMullen and Kittle), University of Kansas Medical Center, Kansas City, Kan.

Footnotes
Received for publication Sept 7, 1967.

Submitted by the authors for the Mitchell I. Rubin Festschrift issue of the JOURNAL.

Reprint requests to 39th and Rainbow, Kansas City, Kan 66103 (Dr. Lauer).

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