Foetal Circulation and Adaptation Flashcards
What is the placenta involved in?
Circulation:
- gas exchange
- nutrition
- waste excretion
- homeostasis
How do foetal lungs differ from adult lungs?
they are deflated and fluid filled
How does the foetal liver differ from the adult liver?
it has little role in nutrition and waste management
How does blood reach the placenta?
via the umbilical arteries
How does blood return from placenta to foetal heart?
via the umbilical vein
3 shunts in foetal heart
ductus venosus, foramen ovale, ductus arteriosus
Ductus venosus
connects to umbilical vein to the IVC
Foramen ovale
opening in atrial septum, connecting RA to LA
Allows best oxygenated blood to enter LA->LV, ascending aorta, carotids
Membrane flap on LA side
Ductus arteriosus
connects pulmonary bifurcation to descending aorta
93% of RV output follows this path- other 7% goes to lungs
Patency maintained by PGE2 (produced by placenta)
What happens to PVR when baby is born?
It decreases as lungs physically expand and circulating oxygen is increases
What happens to SVR when baby is born?
It increases as cord is clamped and cut
Why does flow decrease when baby is born?
Due to decreased PVR
Why does amount of PGE2 circulating decrease when baby is born?
Increased lung metabolism
What happens to shunt when baby is born?
Becomes bidirectional then left to right
When does functional/physiological closure duct occur?
first few hours/ days
When does anatomical duct closure occur?
7-10 days
What group of infants is patent ductus arteriosus common?
Preterm infants
- can contribute to other preterm complications
- treatment is wait and see, NSAIDs and surgery
When is IV PGE2 used
To maintain duct latency in duct dependent circulation until an alternative shunt is established or definitive surgery is carried out
When is normal adult type levels of PVR reached?
2-3 months
Result of failure to of PVR to fall
Persistent pulmonary hypertension
- likely in sick babies ie sepsis, cold stress
- can be related to abnormalities like congenital diaphragmatic hernia
What happens to shunts in PPHN?
They remain
right to left at PFO and PDA
Causes large difference between pre and post ductal pO2
