Ch. 421 - The Fetal to Neonatal Circulatory Transition Flashcards
3 cardiovascular fetal structures important for maintaining a parallel circulation
1) Ductus venosus 2) Foramen ovale 3) Ductus arteriosus
Highest level of O2 provided to the fetus comes from
Umbilical vein
% umbilical venous blood that enters the hepatic circulation
50%
Flap of tissue at the right atrial-inferior vena cava junction
Eustachian valve
Blood from the IVC in the fetus is preferentially routed to
The foramen ovale to the left atrium
Major source of LV blood flow in the fetal circulation
Blood from the RA rather than the pulmonary vein
PO2 of SVC blood
12-14mmHg
Blood from the SVC to the RA preferentially flows to the
Tricuspid valve into the RV
Only approx ___% of RV outflow enters the lungs
5
Majority of RV outlfow enters the ___
Ductus arteriosus into the desending aorta
Total fetal cardiac output
~450ml/kg/min
Approximately ___% of descending aortic blood flow returns to the placenta while the remaining perfuses fetal organs and tissues
65
RV output in the human fetus is ___x that of the LV flow
1.3
T/F During fetal life, the RV is performing a greater volume of work than the LV
T
Leads to rapid decrease in pulmonary resistance at birth
Mechanical expansion of the lungs and increase in arterial pO2
Increase in systemic vascular resistance at birth is brought about by this event
Removal of low-resistance placental circulation
Reversal of flow at the ductus arteriosus from right to left to left to right is due to
Increase in systemic circulatory pressure and decrease in pulmonary circulatory pressure
Brings about closure of the DA
High arterial pO2
Remnant of the DA
Ligamentum arteriosum
Event that leads to closure of the DV
Removal of the placenta from the circulation
Systemic cardiac output at birth
~350ml/kg/min
Medications that may be given to maintain the DA open and close respectively
PGE1 or E2, indomethacin
Largest decline in pulmonary resistance from the fetal to adult levels in the human infant at sea level occurs within
2-3 days, but may be prolonged for 7 days or more
Factors that lead to constriction of the neonatal pulmonary vasculature
1) Acidosis 2) Hypercapnia 3) Hypoxemia
Normal adult cardiac output
75ml/kg/min
The foramen ovale is functionally closed by
3rd month of life
The DA is functionally closed by
10-15 hrs of life
In a full term neonate, ___ is the most important factor controlling ductal closure
O2
When the pO2 of the blood passing through the ductus reaches about ___mmHg, ductal walls begin to constrict
50
T/F The ductus of the premature infant is less responsive to oxygen
T
