Ch. 421 - The Fetal to Neonatal Circulatory Transition

Question 1

3 cardiovascular fetal structures important for maintaining a parallel circulation

Answer 1

1) Ductus venosus 2) Foramen ovale 3) Ductus arteriosus

Question 2

Highest level of O2 provided to the fetus comes from

Answer 2

Umbilical vein

Question 3

% umbilical venous blood that enters the hepatic circulation

Answer 3

50%

Question 4

Flap of tissue at the right atrial-inferior vena cava junction

Answer 4

Eustachian valve

Question 5

Blood from the IVC in the fetus is preferentially routed to

Answer 5

The foramen ovale to the left atrium

Question 6

Major source of LV blood flow in the fetal circulation

Answer 6

Blood from the RA rather than the pulmonary vein

Question 7

PO2 of SVC blood

Answer 7

12-14mmHg

Question 8

Blood from the SVC to the RA preferentially flows to the

Answer 8

Tricuspid valve into the RV

Question 9

Only approx ___% of RV outflow enters the lungs

Answer 9

5

Question 10

Majority of RV outlfow enters the ___

Answer 10

Ductus arteriosus into the desending aorta

Question 11

Total fetal cardiac output

Answer 11

~450ml/kg/min

Question 12

Approximately ___% of descending aortic blood flow returns to the placenta while the remaining perfuses fetal organs and tissues

Answer 12

65

Question 13

RV output in the human fetus is ___x that of the LV flow

Answer 13

1.3

Question 14

T/F During fetal life, the RV is performing a greater volume of work than the LV

Answer 14

T

Question 15

Leads to rapid decrease in pulmonary resistance at birth

Answer 15

Mechanical expansion of the lungs and increase in arterial pO2

Question 16

Increase in systemic vascular resistance at birth is brought about by this event

Answer 16

Removal of low-resistance placental circulation

Question 17

Reversal of flow at the ductus arteriosus from right to left to left to right is due to

Answer 17

Increase in systemic circulatory pressure and decrease in pulmonary circulatory pressure

Question 18

Brings about closure of the DA

Answer 18

High arterial pO2

Question 19

Remnant of the DA

Answer 19

Ligamentum arteriosum

Question 20

Event that leads to closure of the DV

Answer 20

Removal of the placenta from the circulation

Question 21

Systemic cardiac output at birth

Answer 21

~350ml/kg/min

Question 22

Medications that may be given to maintain the DA open and close respectively

Answer 22

PGE1 or E2, indomethacin

Question 23

Largest decline in pulmonary resistance from the fetal to adult levels in the human infant at sea level occurs within

Answer 23

2-3 days, but may be prolonged for 7 days or more

Question 24

Factors that lead to constriction of the neonatal pulmonary vasculature

Answer 24

1) Acidosis 2) Hypercapnia 3) Hypoxemia

Question 25

Normal adult cardiac output

Answer 25

75ml/kg/min

Question 26

The foramen ovale is functionally closed by

Answer 26

3rd month of life

Question 27

The DA is functionally closed by

Answer 27

10-15 hrs of life

Question 28

In a full term neonate, ___ is the most important factor controlling ductal closure

Answer 28

O2

Question 29

When the pO2 of the blood passing through the ductus reaches about ___mmHg, ductal walls begin to constrict

Answer 29

50

Question 30

T/F The ductus of the premature infant is less responsive to oxygen

Answer 30

T