Foetal Circulation Flashcards
What is the order of foetal circulation?
Placenta - heart (small amount to lungs so they can grow) - brain and body - placenta
Where do the umbilical vessels join circulation?
The umbilical arteries branch off the descending aorta. The umbilical vein joins the inferior vena cava delivering oxygenated blood to the system
What are the 3 special aspects to circulation ‘shunts’ in the foetus?
Ductus venosus
Foramen Ovale
Ductus Arteriosus
What is the ductus arteriosus?
Connects pulmonary bifurcation to the descending aorta
7% of the RV output goes to the lungs the rest via the ductus arteriosus joining the descending aorta. The patency of the ductus arteriosus is maintained by prostaglandin E2 produced by the placenta
How does the baby inflate their lungs?
Through crying, the narrowing of the vocal cords and moving air in increases the pressure pushes the fluid out of the lungs and inflates them
What happens to the ductus arteriosus after birth?
It constricts because
- blood begins to flow to the lungs so less flow through the vessels
- there is decreased prostaglandin because the placenta’s gone and the lungs metabolise the prostaglandin
- there is a increased pO2
The vessel closes physiologically in hours and days and anatomically within 7-10 days. It becomes the fibrous ligament - ligamentum arteriosum
What babies more commonly get patent ductus arteriosus?
preterm babies more commonly and can contribute to other preterm complications
- can happen in full term however
What is patent ductus arteriosus?
The failure of the ductus arteriosis to close after birth
How is patent ductus arteriosis treated?
- wait and see sometimes closes as baby matures
- NSAIDs (e.g. ibuprofen) as this helps to get rid of prostaglandin E2
- surgery to close it
What is duct dependent circulation?
When the aorta isn’t properly formed and the duct is needed to get blood from the heart to the body.
Prostaglandin E2 is given to keep the duct open until they can get surgery to fix it
What is persistant pulmonary hypertension of the new born?
The pulmonary resistance has failed to drop and so deoxygenated blood conmtinues to circulate entering the aorta via the foramen ovale and ductus arteriosis and so the baby will be hypoxic
How is persistant pulmonary hypertension of the new born treated?
- ventilation
- oxyenation
- giving inotropes to cause systemic constriction and increase systemic resistance
- Inhaled nitric oxide
- ECMO if nothing else is working and the baby just needs a wee bit more time
What is the function of the placenta?
- foetal homeostasis
- gas exchange
- Acid base balance
- nutrient transport to foetus
- waste product transport from foetus
- hormone production
- IgG transport
- PGE2 production
What is the difference in the foetus compared to adults?
the lungs are unexpanded and fluid filled
the liver has little role in nutrition and waste management
the gut isn’t in use
What is the ductus venosus?
it connects the umbilical vein to the inferior vena cava
the nutrients from the placenta don’t need further processing in the liver so the ductus venosus bypasses the portal circulation for the IVC
