Paediatrics Flashcards
What is the function of the placenta? (8)
Foetal homeostasisGas exchangeAcid base balanceNutrient transport to foetusWaste product transport from foetusHormone productionTransport of IgG (crosses the placenta from mother to baby protecting the baby while their humoral response is developing)PGE2 (helps to maintain duct potency in utero.)
In utero, what is the state of the baby’s lungs?
Fluid filled and unexpanded (the liver has little role in nutrition and waste management and the gut is not in use)
What blood vessels carry blood to and from the foetal heart to the placenta?
The foetal heart pumps blood to the placenta via the umbilical arteries and blood from the placenta returns to the foetus via the umbilical vein
What are the 3 blood vessels in the umbilical cord?
2 umbilical arteries1 umbilical vein(some babies can only have one artery and one vein - this can be normal but can also be a sign that there are other problems)
What are the 3 foetal shunts?
The ductus venosusThe foramen ovalThe ductus arteriosus
In the foetal circulation, does the right heart or left heart have higher pressure?
The right heart
Which ventricle is dominant in the foetus?
The right ventricle
What does the ductus venous do?
Connects the umbilical vein to the inferior vena cava
What does the foramen ovale do?
Opening in atrial septum connecting RA to LA
What does the ducts arteriosus do?
Connects pulmonary bifurcation to the descending aorta
Why does the ductus venosus exist?
Nutrients coming from placenta don’t need further processing in the liverDuctus venosus carries the majority of the placental blood straight into the IVC bypassing portal circulation
What does foramen ovale allow?
Blood to flow from right to left atriumAllows the best oxygenated blood to enter left atrium then on to LV, ascending aorta, carotidsMembrane flap on left atrium side
Where does the output from the RV go?
Only 7% goes to the lungsThe restless via ductus arteriosus to join descending aorta
What maintains the potency of the ductus arteriosus?
Circulating prostaglandin E2 produced by the placenta
Summary of foetal circulation?
Oxygenated comes from the placenta to the foetus via the umbilical vein.In the liver, the ductus venosus connects the umbilical vein to the IVCThe blood passes into the right sides of the heart and the oxygenated blood passes through the foramen ovale into the left atriumThe blood then passes into the left ventricle and out the aortaBlood coming from the body also enter the right atriumThis deoxygenated blood passes to the right ventricleThe blood is pumped via the pulmonary artery Most of the blood bypasses the lungs and is pumped through the ductus arteriosus where the deoxygenated blood is pumped to the lower half of the foetal body where it leaves via the umbilical arteriesSome blood does pass to the lungs
Why do babies cry when they are first born?
It creates back pressure opening up the alveoli
What are the circulation changes during the first few mins after birth? (3)
First breath = lungs open up, pO2 increases and causes pulmonary vasodilationDecrease in resistance to flow to lungsCord clamping = large, low resistance vascular bed removed from circulation, systemic vascular resistance increasesBaby going pink = more blood circulating to lungs, progressively increasing pO2
What are the O2 sats of the foetus in the womb?
60 - 70%
What causes the foramen ovale flap to close?
As PVR falls and SVR rises, LA pressure exceeds the RA pressure = the flap is pushed closed (stays open in up to 35% of the population = implicated in stroke and migraine)
What causes the ductus arteriosus to close? (3)
Fall in pulmonary vascular resistance reduces blood flow through the ductRising oxygen tension has a direct effect on the duct smooth muscle causing constrictionThe loss of circulating PGE2 from the placenta and increased PGE2 metabolism in the lung
How long does it take for the ductus arteriosus to functionally close?To anatomically close?
hours to days7-10 dats
What does the ductus arteriosus end up as when it closes?
Fibrous ligament called the “ligamentum arteriosum”
What type of babies have a very high incidence of failure of ductus arteriosus closure?
Preterm infants
Treatment options for failure of ductus arteriosus to close?
Wait and seeNSAIDs (cause the duct to close)Surgery (if NSAIDs don’t work)
