Fetal Circulation Flashcards
When is the fetal heart fully developed?
Usually by week 8
List the 3 fetal shunts
- Ductus Venosus
- Foramen Ovale
- Ductus arteriosus
Describe the placement of ductus arteriosus and how it allows for the movement of blood
Ductus arteriosus is a shunt between the ascending aorta and the pulmonary trunk. It allows for oxygenated blood coming into the left ventricle from the umbilical vein to enter into the ascending aorta bypassing the lungs and into systemic circulation
Describe the placement of the foramen ovale and how it allows for the movement of blood
The foramen ovale is located in the right atrium and allows for oxygenated blood to enter into the left atrium bypassing pulmonary circulation in order to reach systemic circulation faster
Describe the placement of ductus venosus and how it allows for movement of blood
Allows oxygenated blood to enter from the umbilical vein to the inferior vena cava and bypass the liver d
Describe the path of blood from the placenta to the right atrium
Placenta
Umbilical Vein (shunt to liver)
Ductus venosus
IVC
Right atrium
Describe the path of blood as it goes from the right atrium to the left atrium
Path 1
1. Right atrium
2. Foramen ovale
3. left atrium
Path 2
1. Right atrium
2. Right ventricle
3. Pulmonary trunk
4. Lungs
5. Left atrium
Describe how blood in the pulmonary trunk can bypass the lungs and return to the umbilical arteries
- Pulmonary trunk
- Ductus arteriosus
- Aorta
- System circulation
- Umbilical arteries
- Placenta
Describe the path of blood in the left atrium as it returns to the placenta
- Left atrium
- left ventricle
- aorta
- systemic circulation
- umbilical arteries
What is the function of the foramen ovale?
Opening of the atrial septum between the right and left atria that shunts oxygen rich blood to the brain and developing body systems
What is the function of the ductus arteriosus?
Connects the pulmonary artery to the aorta
Describe the PVR of the fetus and the factors that make it
In utero, the PRV is high due to the lungs being filled with fluid
What are the factors that aid in the decrease of pulmonary vascular resistance following birth?
- Increasing PaO2
- Pulmonary vasodilation
- Prostaglandins
- Nitric oxide
- removal of lung fluid due to compression during birth
What neonatal difficulties can be present at birth?
- Lack of respiratory effort
- Blockage of airways
- Impaired lung function
- persistent increased pulmonary vascular resistance
- abnormal cardiac structure/function
When does the ductus venosus close functionally?
the ductus venosus closes functionally at the time of the umbilical cord clamping
When does the ductus venosus close anatomically?
the ductus venosus closes anatomically at 14 days
When does the the foramen ovale close functionally?
within minutes of birth due to the expansion of the lungs and the decrease in PVR resulting in higher pressures in the left atrium
When does the ductus arteriosus close functionally?
the ductus arteriosus closes functionally 10-15 hours after birth
When does the ductus arteriosus close anatomically?
anatomic closure of the ductus venosus occurs within 2-3 months
When measuring an infants preductal SpO2, where would you place the SpO2 monitor?
on the right hand
Why is it important to measure an infants SpO2 on the right hand?
- This allows for a reading of preductal blood
- The ductus arteriosus is still open for 10-15 hours after birth and allows for blood to be mixed post ductally, by measuring the SpO2 preductally, we know what oxygen level is reaching the brain of the infant
What vessel is considered preductal?
the brachiocephalic trunk
