● Describe variations in fetal circulation and outline what each structure does in terms of
hemodynamics of blood flow in the fetal heart. Pg. 147
○ Blood leaves the placenta and enters the fetus through the umbilical vein.
○ The ductus venosus, the foramen ovale, and the ductus arteriosus allow the blood to
bypass the fetal liver and lungs
○ Most blood flows through the ductus venosus directly into the fetal inferior vena cava,
bypassing the liver
○ This blood then enters the right atrium, passes through the foramen ovale into the left
atrium, and pours into the left ventricle into the aorta
■ Some blood from head and upper extremities returns by way of the superior vena
cava, is emptied through into the right atrium and passes through the tricuspid
valve into the right ventricle
■ This blood is pumped into the pulmonary artery, and a small amount passes to
the lungs for nourishment only
○ The larger portion of blood passes from the pulmonary artery through the ductus
arteriosus into the descending aorta, bypassing the lungs
○ Blood returns to the placenta through the two umbilical arteries, and the process is
repeated
● What events occur to cause changes in fetal circulation to postnatal circulation? Describe how
these events change flow in the heart of the newborn. Starts at pg. 470
○ Neonate’s first breaths of air initiate a sequence of events that empties the airways of
fluid, establishes volume and function of the newborn’s lungs, and causes fetal circulation
to convert to neonatal circulation
○ Two most important things to help the change in cardiopulmonary adaptation:
■ When the baby’s chest pops out, the first breath happens when atmospheric
pressure is exerted on the chest once it leaves the birth canal
● Empties the airways of fluid, establishes volume and function of the
newborn’s lungs, and causes fetal circulation to convert to neonatal
circulation
■ Clamping of the umbilical cord: placenta is excluded from circulation, cessation of
blood flow through the umbilical vein facilitates collapse of the ductus venosus.
Systemic pressure becomes greater than the pulmonary pressure, causing the
blood to flow in the opposite direction, and the foramen ovale closes. The shunt
across the ductus arteriosus reverses from L to R as pressure increases and causes
it to constrict, leading to closure in the first days of life.
,● Describe closure of these structures by time frame. What interventions are taken if the structures
don’t close?
○ Foramen ovale: 1 to 2 hours after birth.
■ If baby is crying or cold, it will stay open
○ Ductus arteriosus: functional closure begins within 18 hours after birth.
■ Fibrosis or anatomic closure within 2 to 3 weeks.
■ Interventions:
● Closure by device.
● IV ibuprofen or indomethacin only for preemies without CHF, none for
term infants
○ Ductus venosus: related to mechanical pressure changes that result from severing the
cord.
■ Fibrosis or anatomic closure occurs within 2 months.
● Describe the pressures pre and post natal in the pulmonary artery/aorta and the functions of
these two structures.
○ Fetal - blood from pulmonary artery (carries oxygenated blood) to the aorta via ductus
arteriosus
○ Neonatal - reversal of blood flow; now from aorta to pulmonary artery (which now carries
deoxygenated blood) because of increased left atrial pressure; ductus arteriosus begins to
constrict and closes in response to increased oxygen
● Describe the primary principles that guide hemodynamics in the adult.
● What should the nurse assess for in babies who are suspected of having a heart defect? pg. 1194
, ● What do lab tests show for children with cardiac defects? Pg. 1190
○ Desaturated blood - when oxygenated and deoxygenated blood mix
○ Cyanosis - hypoxemia resulting from decreased concentration from oxygenated
hemoglobin
■ Pulse oximeter values for children 95-98%
■ Bone marrow responds to chronic hypoxemia with polycythemia, an excess
production of RBCs to increase amount of hemoglobin available for oxygenation
○ Polycythemia is also associated with platelet dysfunction and puts child at risk for
thromboembolism, especially if they become dehydrated
○ In cyanotic defects, hematocrit value of 50% or higher is common
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