TYK188

Which of the following statements is CORRECT?

a) Right and left ventricular outputs in the fetus are almost identical before birth

b) Functional closure of the foramen ovale follows the increase of systemic vascular resistance and decrease of pulmonary vascular resistance at birth

c) Placental transfer of drugs and toxins put the fetus at increased risk because all blood from the umbilical veins bypasses the fetal liver

d) The ductus arteriosus is the first fetal shunt to functionally close in the postnatal period

e) Oxygen saturation in the descending aorta is similar between a fetus and a 5 year-old child

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Answer

Answer b.

The ratio of right to left fetal cardiac outputs is 1.3:1; about 50% of umbilical venous blood flow actually goes to the liver; the first shunt to functionally close after the first breath of the neonate is the foramen ovale; blood with the highest oxygen saturation perfuses the upper part of the fetal body, the lower part receives less well saturated blood, largely because of preferential streaming of desaturated blood from the superior vena cava into the right ventricle toward the pulmonary artery from where it shunts back into the systemic circulation via the ductus arteriosus and thereby lowers the saturation in the descending aorta.

Notes

This question originally printed in the Pediatric Anesthesiology Review Topics kindle book series, and appears courtesy of Naerthwyn Press, LLC.

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