Neonatal Physiology Flashcards
What is the purpose of fetal circulation
1- receives oxygenated purified and detoxified blood via umbilical vein
2- distributed blood and then returns it to umbilical arteries
Why is excess circulation to liver and lungs be wasted and what does that mean in fetal circulation
Because function of these organs is done by mothers circulation, circulation to these organs is partially bypassed
Explain fetal circulation
1- oxygenated blood from umbilical vein will pass through liver ( end up at IVC ) and 50% will bypass and go through ductus venous to IVC
2- Mixed oxygenated blood will then go into right atrium and divides into 2 streams that don’t mix
3- Most of the blood will go straight to left atrium via foramen oval that will go into aorta and up into the head & arms
4- blood from head will come back down via SVC into right atrium and right ventricle and then instead of going to lung it will go to bottom of fetus ( lower limbs) via ductus arteriosus.
5- blood then returns to placenta via umbilical artery
What happens to fetal circulation at birth
Infant must take over gas exchange and detoxification so fetal circulation is divided into systemic and pulmonary circulations..
Explain the changes of fetal circulation at birth
1- Umbilical arteries and veins will be clamped up = cause rise in peripheral resistance in systemic circulation = rise in BP
2- Lungs expand as first breath is taken causing increase of oxygen tension = reduction in pulmonary vascular resistance
3- pressure in right atrium and ventricle and pulmonary trunk falls = causing foramen ovale to close and fibroses in first months
5- foramen ovale closing causes blood to go from right atrium to right ventricle not left atrium and then into pulmonary trunk to go to lungs for oxygenation
4- Ductus arterioles closes within first few days due to high oxygen tension causing oxygenated blood to be sent to lungs for function
5- ductus venous closes 1-3 hours after birth via fibrosis
What happens if lungs don’t start functioning immediately after birth
Brain anoxia and damage
Explain respiratory adjustment at birth
1- Initial breath requires large inspiratory intrapleural pressure to develop to overcome surface tension of fluid that’s filling alveoli
2- intrapleural pressure rapide reduces after but neonatal lung compliance is still less than average adult
3- active expiration rather than passive to overcome resistance from fluid in airways ( like we get in exercise )
What’s the difference between expiration in newborn and adult
Newborn : active expiration
Adult : passive expiration
What’s the respiratory rate of a newborn
40 breaths a minute & 650 ml , twice the adult ventilation
Explain weight changes in the first days
Newborn drips in weight in the first days due to difficulties in breastfeeding. By day 10 this is resolved and then weight triples in first year.
What nutrition is in demand first year of life
Iron, calcium and Vitamin D
Explain changes in thermoregulation after birth
Initial drop of 1-2 degrees in infant that resolves in first 12 hours.
With twice metabolic rate of adult , infants generate more heat. There are still fluctuations in core temperature due to immature thermoregulatory mechanisms.
What is brown fat
Fat that instead of producing ADP it produces heat. In infants this counters changes in thermoregulation
Explain Liver function after birth
Rise in plasma bilirubin ( 5x) for the first 1-2 weeks since liver is poorly formed at birth.
Glycogen storage and manufacture is compromised and plasma protein levels could be low.
As liver matures this is all fixed in a few months
What is necessary after birth due to compromising of glycogen
Frequent feeding
