Regional Redistribution of Blood Flow in the Mature Fetal Lamb

Observations on mature fetal lambs delivered under chloralose anesthesia showed that variations in arterial blood gas tensions, caused by ventilation with gas mixtures of differing composition, produced considerable changes in regional systemic blood flows measured with a cannulated electromagnetic flowmeter. Partial asphyxia was associated with a rise in arterial pressure and a reduction in femoral and renal flows; coronary, carotid and superior sagittal venous sinus flows increased owing mainly to coronary and cerebral vasodilatation. Ventilation with air caused an opposite result. The results indicate that a more detailed study of the local and reflex mechanisms controlling vasomotor tone in the mature fetus is necessary.