Fetal Transition

Question 1

5 key steps for successful cardio pulm transition

Answer 1

lung maturity (surfactant, gas exchange), absorption of lung fluid, onset of breathing (lower PVR, lung expansion), increased blood O2, loss of placental circulation (increase SVR and close shunts)

Question 2

describe fetal pulm circulation

Answer 2

hypoxic- O2 sat 50%

suppressed NO and PG

this increases PVR, if excessive can lead to vascular remodeling

Question 3

how do fetuses increase CO

Answer 3

through increasing HR, no help from starling (increased preload)

Question 4

cortisol impact on lung maturation

Answer 4

influences angiogenesis, enhances lung fluid clearance and surfactant production, matures parenchyma

increases 30-36 wks

glucocorticoids used therapeutically w/ prematurity

Question 5

describe fetal lung fluid and its role

Answer 5

actively secreted by distal lung epithelia- rich in Cl- and K+ (water follows these ions), different from amniotic fluid, helps expand fetal lung

Question 6

fetal lung clearance process

Answer 6

begins days before labor, requires lung epithelium to switch from production to absorption

labor induces mechanincal and non (catecholamines, glucoricoids, etc) forces

fluid drained via pulm circulation and lymphatics to interstitium

Question 7

importance of first breath

Answer 7

needs surfactant to establish FRC on end expiration, this makes continual breathing easier

Question 8

closure of ductus venosus

Answer 8

functional closed at birth, anatomic at 1 wk

Question 9

closure of ductus arteriosus

Answer 9

functional at around a day, anatomic at 4-8 wks

Question 10

closure of foramen ovale

Answer 10

functional at birth, anatomic months to yrs

Question 11

what closes shunts?

Answer 11

switch to higher SVR than PVR as umbilical cord is clamped (increased SVR) and lungs inflate (lower PVR)

Question 12

early vs delayed cord clamping

Answer 12

early: no ventilation est., PVR still high so reduced venous return w/o placenta, reduced CO and systemic BP rises (perinatal ischemic event)
delayed: ventilation est., PVR decreases and pulm CO established, venous return maintained and rise in BP avoided

Question 13

consequences/causes of persistent pulm HTN of newborn

Answer 13

shunts fail to close, right to left shunt causes hypoxic state

caused by inadequate surfactant or fluid filled alveoli (meconium aspiration, pneumonia)