Foetal Circulation & Adaptation at Birth Flashcards
what are 8 functions of the placenta?
1) fetal homeostasis
2) gas exchange
3) acid base balance
4) nutrient transport to foetus
5) waste product transport from fetus
6) hormone production
7) transport of IgG
8) PGE2
what are the lungs like in fetus?
lungs are filled with fluid and unexpanded
what is the liver like in foetus?
little role in nutrition and waste management
what is the gut like in the foetus?
no in use
where does the foetal heart pump blood to and what does it do this via?
to the placenta via the umbilical arteries
where does the blood from the placenta go and what does it do this via?
returns to foetus via the umbilical vein
what is a challenge for the foetus?
- oxygenated, nutrient rich blood returns from placenta to right side of heart & needs to be distributed to growing foetus
what are the 3 shunts specific to foetal life?
1) ductus venosus
2) foramen ovale
3) ductus arteriosus
what does the ductus venosus connect?
= connects the umbilical vein to inferior vena cava
what does the foramen oval represent and what does it connect?
= opening in atrial septum connecting RA to LA
what does the ductus arteriosus connect?
= connects pulmonary bifurcation to descending aorta
what do the ductus venosus carry and where to?
majority of placental blood straight into IVC bypassing portal circulation
what does the foramen oval allow? (2)
1) allows blood flow from right to left atrium
2) allows best oxygenated blood toe enter left atrium then onto LV, ascending aorta, carotids
what is there on the left atrium side?
membrane flap
what percentage of RV output goes to lungs?
where does the rest of the RV output go?
only 7%
= rest goes via ductus arteriosus to join descending aorta
how is patency of ductus arteriosus maintained?
= by circulating prostaglandins E2 produced by placenta
what adaptations happen minutes following birth?
1) baby inflates lungs & cries
2) goes from blue to pink
3) cord clamped and cut
how is pulmonary vascular resistance (PVR) decreased in the foetus?
- breath in = lungs expand
- increased circulating oxygen
how is systemic vascular resistance (SVR) increased in the foetus?
- cord clamped and cut
as PVR falls and SVR rises what happens;
1) to the LA pressure compared to RA pressure?
2) to the flap?
1) LA pressure exceeds RA pressure
2) flap is pushed closed
what happens within the first few hours and days to the ductus arteriosus?
= closes due to construction
Within hours to days;
- functional closure
Within 7-10 days
- anatomical closure
what does the ductus arteriosus end up as?
= fibrous ligament
e.g. ligamentum arteriosum
in what situation is it most common to develop failure of duct closure?
= in premature babies
what are the treatment options for failure of duct closure?
= wait and see
= NSAIDS
= surgery
what do some congenital heart diseases cause?
= duct dependent circulation
what can be used to keep the duct open?
= IV prostaglandin E2 until an alternative shunt is established or definitive surgery carried out.
when does pulmonary resistance reach normal adults type levels?
= by 2-3months
when is the failure of adaptation in foetus most likely to happen?
= in sick babies
1) sepsis
2) hypoxic ischaemic insult
3) meconium aspiration syndrome
4) cold stress
what can failure of adaptation be related to?
= underlying anatomical abnormality
e.g. congenital diaphragmatic hernia
what is an example of a problem that could happen as a result of failure to adapt?
= persistent pulmonary hypertension of newborn
what happens to lung vascular resistance, shunts and babies colour in persistent pulmonary hypertension of newborn (PPHN)?
Lung vascular resistance
= fails to fall
Shunts remain
= right to left flow at PFO
= right to left flow at PDA
Baby
= blue
In PPHN, describe the pre and post ductal oxygen saturation?
there is a large difference.
how would you treat PPHN?
- ventilation
- oxygenation
- maintain high systemic blood pressure
- inhaled nitric oxide
- ECLS
how would you reduce PVR?
- oxygen
- ventilation
- sedation
- thermo-regulation
- correction of acidosis
- treatment of sepsis
- inhaled nitric oxide
how would you increased SYV
- maintain higher than adequate BP
- inotropes
- support other organ function
- in severe cases extra corporeal life supply
