Fetal and Neonatal Circulation Flashcards
In fetal circulation, when does the heart begin to develop?
by 3rd week, development of the heart begins
In fetal circulation, when does the atria form?
by 5th week, the atria are formed
in fetal circulation, when do the ventricles form?
by 5th week, the ventricles form
when does fetal circulation develop?
3rd week, embryonic blood vessels develop
when does the first heart beat happen?what is the heart rate? and prior to delivery?
4th week; 65 beats/min; 140 beats/min
what is the fetal circulatory system adapted to maximize?
gas and nutrient exchange between the mother
and the fetus
what is the fetal circulatory system adapted to provide?
a higher supply of oxygen to the developing organs with
high metabolic demand by bypassing the organs with low metabolic demand
what organs of the fetus require high demand of the fetal circulatory system?
heart, brain, upper body
what organs of the fetus require low demand of the fetal circulatory system?
liver, lungs, lower body
what is the fluid dynamics law?
Any fluid/gas will move from the area of higher pressure to the area of low pressure (including blood)
compare and contrast adult circulation with fetal circulation?
Adult circulation:
High pressure: Systemic circulation (left heart)
Low Pressure: Pulmonary circulation (right heart)
Fetal Circulation: High Pressure: Pulmonary Circulation (collapsed lungs, constricted vascular tree) Low Pressure: Systemic Circulation (aorta and placenta)
what is the function of the shunt?
used inorder to maximize the perfusion of the organs with the high metabolic rate because babies lungs are collapsed and so blood comes from the mother
what are the four shunts in order?
placenta, ductus venosus, foramen ovale, ductus arteriosus
what is the placenta?
the first shunt used for fetal circulation and is a low resistance organ. It replaces the four separate organs: the lungs, GI system, Liver, and Kidneys
Gas exchange
nutriton and fluid regulation
nutrition and waste removal
fluid excretion and ion regulation
what percentage of blood does the fetal heart pump through the placenta?
40%
this shunt receives most of the combined cardiac output (CCO)?
the placenta
Blood flow from the mother to the placenta via?
Uterine arteries
Blood flow from the placenta to the mother via?
Uterine veins
Blood flow from the fetus to placenta via?
Umbilical arteries (two)
(deoxygenated blood, venous)
Capillaries
Villi
Blood flow from the placenta to the fetus via?
Umbilical Vein (one) (oxygenated blood, arterial)
what is the function of the umbilical arteries?
carry deoxygenated blood away from the fetus
what is the function of the umbilical veins?
carries oxygenated blood towards the fetus
what is the second shunt?
ductus venosus
what is the function of the second shunt?
shunts a portion of the left umbilical vein blood flow directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.
what is the ductus venosus regulated by?
the sphincter
what percentage of CCO (combined cardiac output) passes through the ductus venosus?
50%
what is the third shunt?
foramen ovale
where is the third shunt located?
The oval hole in the septum which divides the right and the left atria (posterior wall of the right atrium)
what percentage of the CCO shunts through the foramen ovale?
27%
once the blood shunts from the right atrium to the left atrium what happens to the baby’s heart?
the baby’s heart can function normally
Supplied with increased O2 blood (IVC)
Receives some decreased O2 blood from the upper body (SVC)
in terms of the shunt (foramen ovale) moving from right to left, what happens to the decreased oxygen from the SVC?
sent to the right ventricle (through the tricuspid valve) and towards the lungs
what is the fourth shunt?
ductus arteriosus
what is the function of the fourth shunt? because of this shunt, how are collapsed lungs affected, the aorta?
Diverts the blood from the pulmonary artery in to the aorta to systemic circulation and out via umbilical arteries, this is viewed as a right to left shunt because blood is pushed by mom so higher pressure
HIGHER PRESSURE ON RIGHT SIDE IN DEVELOPING FETUS
Collapsed lungs- increasedresistance
Aorta- decreased resistance (placenta)
what leaves before the ductus arteriosus happens?
carotid arteries
what is the composition of the Fetal HB? why is this important to note? what is the Hb concentration? is cardiac output high?
2 alpha and 2 gamma; it can carry 20-30% more O2 than the adult HB because the chains of the fetal hemoglobin have higher affinity for the oxygen than its adult form which is comprised of 2 alpha and 2 beta, shifts the curve to the left
the Hb concentration is high (Hit 40-60%)
the cardiac output is high too
after birth, what causes our first breath?
physical stress during birth
sudden exposure to external temperature
post-birth hypoxia and hypercapnia
what are the mechanisms that trigger the shift from the fetal to the adult circulation?
newborn breathing and removal of the placenta
what is the effect of newborn breathing?
decrease pulmonary resistance
what is the effect of the removal of the placenta?
increase systemic vascular resistance, the placenta must be removed
what happens to the aortic pressure (systemic) after the removal of the placenta?
there is a sudden increase in the aortic pressure and pulmonary vascular resistance drops.
after delivery, we know that the pulmonary system is affected, what is the effect of the first breath?
it leads to the expansion of the lungs (powerful)
after delivery, we know that the pulmonary system is affected, is there an increase or decrease in pulmonary arterial pressure? right ventricular and atrial pressure? what can this drop in pressure be attributed too?
increase; increase, increase; O2 induced vasodilation
during fetal circulation, pressure flows from which atria? what about after delivery, what happens to the pressure in each of the atria?
right to left; the foramen ovale closes and a high pressure system is created in the left atrium and a low pressure system is created in right atrium
what happens when surfactant is not properly made and the ductus arteriosus does not close properly?
lungs will not function properly and atelectasis can develop
what is the effect of ductus arteriosus closure?
- cessation of blood flow due to closing of the umbilical vein
- blood backs up from the portal vein
- DV smooth muscle contracts
- increase in portal vein pressure-perfusion to the liver
what is the most important step after the delivery of the baby?
the closure of the ductus arteriosus (last to close) because if it stays open and they have a cardiac abnormality this has to be open otherwise the baby will die and this is done through a decrease in pulmonary pressure and increase in systemic pressure and can be maintained by the prostaglandins (keeps it open)
what drug can we give to close the Ductus arteriosus?
indomethacin
what is Patent Ductus Arteriosus (PDA)?
a left to right shunt develops and so failure of ductus arteriosus to close occurs and so their is an increase in aortic pressure leading to increase in blood flow through the PDA in to the pulmonary circulation thus increasing the pulmonary pressure
what are congenital anomalies? examples?
malformations that occur during the embryonic development
Stenosis
Anomaly that causes a blood to flow from the left heart (systemic) to the right heart (pulmonary circulation)
Anomaly that causes blood to flow from the right heart (pulmonary) to the left heart (systemic circulation)
what type of shunt is PDA?
a left to right shunt
what type of shunt is Tetralogy of Fallout?
A Right to Left Shunt
Blue Baby
what are the anomalies of Tetralogy of Fallout?
Aorta-originates from the right ventricle riding on the septum
Stenosis of pulmonary artery (bypass lungs)
Blood from the Right ventricle passes trough the septal defect
/the overriding aorta
Right ventricle enlargement
what is the major problem with Tetralogy of Fallout (ToF)?
shunting of the blood from the pulmonary system → the systemic circulation
what percentage of blood bypasses the lungs in ToF?
75 % of the blood bypasses the lungs with PDA saving the babies life
what are the signs of ToF?
cyanotic baby with increased right ventricle systolic pressure and so we see the enlargement of the right ventricle
treatment for ToF?
Surgical: Dilate the pulmonary stenosis, Close the septal defect, Reconstruct the aorta
what is the life expectancy of ToF?
2-3 (without the surgery) 50 years (after the surgery)
The cause of congenital heart defects before vaccinations was commonly caused by? secondary cause?
german measles; genetics: Some populations more prone for defects
