Mod IV: Fetal Circulation

Question 1

_{Pediatric Physiology​ - Terminology}

0-1 mos. old

Answer 1

Neonate

Question 2

_{Pediatric Physiology​ - Terminology}

1 mos-12 mos. old

Answer 2

Infant

Question 3

_{Pediatric Physiology​ - Terminology}

1-3 years of age

Answer 3

Toddler

Question 4

_{Pediatric Physiology​ - Terminology}

4-14 years of age

Answer 4

Smaller Children

Question 5

_{Pediatric Physiology​ - Terminology}

A Preterm is defined as “a viable infant born after xxth week, but before yyth week of gestation”?

Answer 5

20th week

37th week

Question 6

_{Pediatric Physiology​ - Terminology}

weeks after conception

Answer 6

Postconceptual age

Question 7

_{Pediatric Physiology​ - Terminology}

Why is this important to consider Postconceptual age?

For example: a Preterm born 10 weeks ago at 26 weeks gestation is technically how old?

Answer 7

10 weeks old

Question 8

_{Pediatric Physiology​ - Terminology}

What’s the Postconceptual age (PCA) of a Preterm born 10 weeks ago at 26 weeks gestation?

Answer 8

36 weeks PCA

Although technically, that infant in 2 mo old

However, their Postconceptual age is only 36 weeks

This should be taken into account when thinking about their plan of care

Question 9

_{Pediatric Physiology​ - Terminology}

For mutiple births, how much time could be substracted from the PCA to adequately assess developmental age?

Answer 9

1 week

Question 10

_{Pediatric Physiology​ - Terminology}

Conception to 8 weeks:

Answer 10

Embryo

Question 11

_{Pediatric Physiology​ - Terminology}

8 weeks after conception to birth:

Answer 11

Featus

Question 12

_{Pediatric Physiology - Fetal Circulation}

T/F: Fetal lungs are functional

Answer 12

False

Fetal lungs are nonfunctional

Fetal lungs are resistant to blood flow

Question 13

_{Pediatric Physiology - Fetal Circulation}

Why are fetal lungs resistant to blood flow?

Answer 13

Fluid filled

Question 14

_{Pediatric Physiology - Fetal Circulation}

How do fetal lungs ensure nourishment for growth?

Answer 14

Receive enough blood flow to ensure nourishment for growth

Question 15

_{Pediatric Physiology - Fetal Circulation}

What does the fetus depend on for oxygenation and ventilation?

Answer 15

Placental circulation

Question 16

_{Pediatric Physiology - Fetal Circulation}

The fetal circulation is marquedly different from the adult circulation because. Fetal gas exchange does not occur in the lungs but where?

Answer 16

In the placenta

The placenta must therefore recieve de-oxygenated blood for the fetal systemic organs and return its oxygen rich venous drainage in to the fetus arterial systemic circulation

Question 17

_{Pediatric Physiology - Fetal Circulation}

In addition, the fetal cardiovascular circulation is designed in such a way that the most highly oxygenated blood is delivered to which fetal organs?

Answer 17

Myocardium and the Brain

Question 18

_{Pediatric Physiology - Fetal Circulation}

Why is fetal circulation termed “shunt-dependent circulation”?

Answer 18

Circulatory adaptions are achieved in the fetus by both

Preferential streaming of oxygenated blood

Presence of intra and extra cardiac shunts

Question 19

_{Pediatric Physiology - Fetal Circulation}

Name three structures that are exclusive to fetal circulation:

Answer 19

Ductus Venosus

Foramen Ovale

Ductus Arterious

Question 20

_{Pediatric Physiology - Fetal Circulation}

Name five important adaptions of fetal circulation:

Answer 20

Umbilical vein (1)

Ductus venosus

Foramen ovale

Ductus arteriosus

Umbilical arteries (2)

Question 21

_{Pediatric Physiology - Fetal Circulation}

T/F: Clamping of the umbilical cord after delivery is painful to the infant

Answer 21

False

Clamping of the umbilical cord after delivery is not painful because the umbilical cord does not contain nerves

Question 22

_{Pediatric Physiology - Fetal Circulation}

Temporary organ that connects the developing fetus via the umbilical cord to the uterine wall to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother’s blood supply; to fight against internal infection; and to produce hormones which support pregnancy. This organ is also known as:

Answer 22

Placenta

Question 23

_{Pediatric Physiology - Fetal Circulation}

Vessel that carries oxygenated blood from placenta to fetus

Answer 23

Umbilical vein

_{(Considered the first adaptation)}

Question 24

_{Pediatric Physiology - Fetal Circulation}

Blood from the umbilical vein can either enter the fetal liver and take a while going throught the liver to reach the fetal IVC or it can bypass the the liver and enter the IVC directly via a second fetal adaptation called:

Answer 24

Ductus venosus

^{(connects veins)}

This is a shortcut from the umbilical vein to the IVC

Pass the Ductus venosus, highly oxygenated blood from the umbilical vein meets up with deoxygenated blood from the IVC and that blood dumps in to the RA

Question 25

_{Pediatric Physiology - Fetal Circulation}

Blood in the fetal RA is coming from where? How is its oxygen content?

Answer 25

Mixed umbilical and IVC blood

Blood draining from the SVC

Blood in the RA is even more mixed at this point

Question 26

_{Pediatric Physiology - Fetal Circulation}

Where could blood flow after the RA?

Answer 26

From the fetal RA, blood can flow

Down the RV. Some of the blood will do this. Blood down this path will get squeezed into the Pulmonary trunk, and to each PA

Remember, as that blood approaches the lungs, we need to remember what’s happening inside the lungs

Question 27

_{Pediatric Physiology - Fetal Circulation}

Alevoli in the fetal lungs are filled with:

Answer 27

Fluid

And going pass those fluid-filled alveoli are little blood vessels (arterioles)

Fluid filled alveoli lack oxygen

Question 28

_{Pediatric Physiology - Fetal Circulation}

The process whereby, fluid-filled alveoli lacking oxygen help constrict pulmonary arterioles is called”

Answer 28

Hypoxic pulmonary vasoconstriction (HPV)

Arterioles have smooth muscles

The lack of oxygen in the surrounding alveoli will cause the arterioles smooth muscles to constrict

This increases the resistance of the arterioles

This phenomenom involes millions of alveoli and result in increase resistance in the entire lung

Question 29

_{Pediatric Physiology - Fetal Circulation}

D/t increaseed lung resistance caused by hypoxic pulmonary vasoconstriction, how are PA pressures? What’s the overall effect on fetal blood flow via this route?

Answer 29

The pressure in the PA will be very high

So, for it to be forward flow of blood via this route, there needs to be a lot of flow in the RV, and therefore the RA

Question 30

_{Pediatric Physiology - Fetal Circulation}

As a results, pressures on the right heart become quite elvated, to the point where pressures in the RA become higher that pressures in the LA. Consequently, some blood will flow from the RA to the LA across a passage known as

Answer 30

Foramen Ovale

So, from the RA, some blood will go down the RV, and some blood will go across to the LA via the Foramen ovale

Question 31

_{Pediatric Physiology - Fetal Circulation}

You actually don’t have that much blood coming back through the pulmonary veins, why is that?

Answer 31

b/c of foramen ovale allows high pressures in the RA to go across the LA

This is quite useful b/c as you have blood going across to the LA, you actually don’t have that much blood coming back through the pulmonary veins

In addition it’s hard to get blood flowing through the lungs, d/t the increased resistance there

Still, a litle bit of blood will come through the pulmonary veins, and you have some blood coming from the RA into the LA via the foramen ovale

Question 32

_{Pediatric Physiology - Fetal Circulation}

Where does blood from the LA flows next?

Answer 32

To the LV where it gets squeezed into the aorta, and

the aorta distributes blood througout the rest of the body

Question 33

_{Pediatric Physiology - Fetal Circulation}

Going back to the right side of the heart, It’s important to note that some blood will flow from the RV to the PA and directly to the aorta via a vessel or passage called

Answer 33

Ductus arteriosus

Remember that the PA has very high pressures d/t the high resistance in the fluid-filled lungs

Blood will go from high pressures (PA) to low pressures (aorta)

The Ductus arteriosus also explains why we don’t have that much blood coming from the pulmonary veins since much of the blood that’s pumped into the pulmnary trunk by the RV ends up going into the aorta via the Ductus arteriosus, not into the lungs

Question 34

_{Pediatric Physiology - Fetal Circulation}

Some of the blood that goes down the descending aorta will also flow into the internal iliac arteries, from which, vessels carry de-oxygenated blood back to the placenta. These vessels are called:

Answer 34

Umbilical areteries

They bring blood back to the placenta; and these are very high flow vessels

Question 35

_{Pediatric Physiology - Fetal Circulation}

What facilitates blood flow from the faetus back to the placenta via the two umbilical arteries?

Answer 35

Very low resistance of the placenta

Just as the lungs have a very high resistance and divert blood away from it, the placenta has a very low resistance and diverts blood towards it

Question 36

_{Pediatric Physiology - Fetal Circulation}

What are the two initial adaptations to infant circulation after birth?

Answer 36

The placenta is removed from the infant circulation

The lungs get used to bring in air in for the first time

These two events will cause other adaptations

Question 37

_{Pediatric Physiology - Fetal Circulation}

After delivery, an umbilical clamp is placed to the cord. Is this painful to the infant?

Answer 37

No

The umbilical cord doesn’t have nerves

Question 38

_{Pediatric Physiology - Fetal Circulation}

Substance that starts contracting around the two umbilical arteries and the umbilical vein as soon as the temperature falls d/t exposure outside the woumb

Answer 38

Wharton’s jelly

Contraction of Wharton’s jelly will squeeze down on all the vessels inside it (the imbilical vein and the two umbilical arteries)

The fetal circulation goes from being exposed to low resistance placental circulation to high resistance from both the mechanical clamp and from Wharton’s jelly contracting the umbilical vessels

Question 39

_{Pediatric Physiology - Fetal Circulation}

After birth and separation from the placenta, when does blood flow through the umbilical vein ceases?

Answer 39

Over the next few days

Removal of the placenta creates high resistance

The umbilical vein start building clots all the way to the Ductus venosus

Blood flow through the umbilical ceases over the nex few days

De-oxygenated blood flow through the ICV continues

Question 40

_{Pediatric Physiology - Fetal Circulation}

After birth and separation from the placenta, decribe blood flow on the right side of the infant’s heart?

Answer 40

De-oxygenated blood that flows through the IVC continues

This blood has no new fresh oxygenated blood to mix with

It flows to the RA where it mixes with de-oxygenated blood from the SVC

Flows continues down to the RV, and blood is pumped into the pulmonary trunk, to the PAs and finally to the lungs

Question 41

_{Pediatric Physiology - Fetal Circulation}

Explain why resistance in the infant’s lungs fall following the first few breaths after birth?

Answer 41

In-utero, the fetal lungs are a fluid-filled high resistance environment

After the infant takes their first breath, fluid in the lungs is replaced with air. Air pushes the fluid out

Fluid will enter the capillaries. Before the capillaries you have the arterioles that were constricted d/t HPV

But now that air can enter the alveoli, O2 levels are rising in the alveoli

O2 levels are rising sends a signal to the arterioles to dilate

As a result, resistance in the lungs will fall

Question 42

_{Pediatric Physiology - Fetal Circulation}

Explain how pressures on the right side of the infant’s heart fall following the first few breaths after birth?

Answer 42

After lung resistance falls following the first few breaths after birth, de-oxygenated blood can now flow into the lungs, from the PAs

Remember that not that much blood was flowing into the lungs in-utero from the PAs because of the fluid-filled high resistant lungs

Blood flowing into low resistance lungs from the PAs will cause RV and RA pressures to fall as well

The entire right side of the heart is now working under lower pressures

Question 43

_{Pediatric Physiology - Fetal Circulation}

Explain the physiological changes that lead to closure of the Foramen ovale after birth. How soon does this happen after the infant if out of the uterus?

Answer 43

Lower resistance in the lungs allows more blood enter the lungs from the PAs

Blood is now oxygenated in the lungs and returned back to the LA via the pulmonary veins

This is different from before birth where there was not that much blood flowing into the LA from the pulmonary veins

The combination of pressures falling on the right side and more blood coming in through the pulmonary veins will cause increased LA pressures, which in turn will cause the Foramen ovale to close off

Closure of the Foramen ovale happens within minutes after birth

Blood from the LA goes down the LV, and gets pumped into the aorta

Question 44

_{Pediatric Physiology - Fetal Circulation}

Now remember that blood was moving from the PA to the aorta via the Ductus arteriosus because pressure in the PAs were higher that pressure in the aorta. What happens now that pressures in the lungs and PAs are lower?

Answer 44

In the first few hours of life, smooth muscles in the walls of the Ductus arteriosus will sense that O2 levels are higher and will start to constrict

In addition, the Ductus arteriosus can sense that the placenta is removed via the drop in prostaglandins levels; prostaglandins are made by the placenta

When protaglandins levels fall, the Ductus arteriosus is more willing or able to close dowm

Smooth muscles in the walls of the Ductus arteriosus will sense that O2 levels are higher and that prostaglandins levels are down, and these smooth muscles will start to constrict closing the Ductus arteriosus off

The begining of the Ductus arteriosus constricting and closing off happens just a few hours after bitrh

Question 45

_{Pediatric Physiology - Fetal Circulation}

How does the Ductus arteriosus senses that placenta has been removed?

Answer 45

Ductus arteriosus can sense that the placenta is removed via the drop in prostaglandins levels; prostaglandins are made by the placenta

When protaglandins levels fall, the Ductus arteriosus is more willing or able to close dowm

Question 46

_{Pediatric Physiology - Fetal Circulation}

When does the Ductus arteriosus begins to constrict?

Answer 46

The begining of the Ductus arteriosus constricting and closing off happens just a few hours after bitrh

Question 47

_{Pediatric Physiology - Fetal Circulation}

What happens to blood flow to the umbilical arteries after birth?

Answer 47

Blood flows from the aorta down the descending aorta, to the internal iliac branches from which the umbilical arteries branch off

Blood flow continues to the vessels branching off the internal iliac arteries, but there will be no blood flow to the umbilical aretery remnants

Question 48

_{Pediatric Physiology - Fetal Circulation}

Blood flow continues to the vessels branching off the internal iliac arteries, but there will be no blood flow to the umbilical aretery remnants, why?

Answer 48

b/c the resistance there is so high

In addition, the umbilical arteries, just like the ductus arteriosus, have smooth muscles in them, which will respond to the very high O2 levels and to low prostaglandins levels and will start constricting

This process happens over the course of a few hours

Question 49

_{Pediatric Physiology - Fetal Circulation}

How does the high oxygenated blood travels around and through the fetal heart from the placenta?

Answer 49

Placenta → 1 Umbilical Vein → Ductus Venosus → IVC → RA → Foramen Ovale → LA → LV → ascend. Ao → Head & Upper extremity vessels

Question 50

_{Pediatric Physiology - Fetal Circulation}

What’s the O2 saturation level of blood in the umbilical vein?

Answer 50

80-90%

Question 51

_{Pediatric Physiology - Fetal Circulation}

How does the low oxygenated blood travels around and through the fetal heart from the SVC?

Answer 51

SVC → RA → RV → pulmonary trunk → Ductus Arteriosus → descending Ao → lower body → exits via 2 Umbilical Arteries to placenta

Question 52

_{Pediatric Physiology - Fetal Circulation}

What’s the O2 saturation of blood returning to the placenta via the umbilical arteries?

Answer 52

25-40% oxygenated

Question 53

_{Pediatric Physiology - Transitional Circulation at Birth}

Which events lead to the functional closure of the Foramen Ovale after birth?

Answer 53

Cord Clamped => ↑ SVR & ↓ Venous Return

=> LAP > RAP => Functional Closure of the Foramen ovale

=> Blood Flow to Lungs Begins

(and the lungs begin gas exchange)

Question 54

_{Pediatric Physiology - Transitional Circulation at Birth}

Which events lead to the Ductus venosus Closure after birth?

Answer 54

Cord Clamped => ↓ Venous Return (↓ Portal BP)

=> Mechanical Closure (3-7 days)

=> Blood Flow to Liver/Lung

Question 55

_{Pediatric Physiology - Transitional Circulation at Birth}

Over what period of time does Ductus venosus closure happens?

Answer 55

3-7 days

Question 56

_{Pediatric Physiology - Transitional Circulation at Birth}

Ductus venosus closure allows blood to flow to which organs?

Answer 56

Liver & Lungs

Question 57

_{Pediatric Physiology - Transitional Circulation at Birth}

Which events lead to the Ductus Arteriosus Closure after birth?

Answer 57

PVR (lung expansion) + ↑ SVR (cord clamp)

=>L – R shunting Blood from Ao → PA => ↑ PaO2

=> Initial Constriction (few hours after birth)

=> Functional Closure (1-4 days)

=> Anatomical Closure (2-3wks)

Question 58

_{Pediatric Physiology - Transitional Circulation at Birth}

When does Initial Constriction of the Ductus Arteriosus happens?

Answer 58

(few hours after birth)

Question 59

_{Pediatric Physiology - Transitional Circulation at Birth}

When does the Functional Closure of the Ductus Arteriosus happens?

Answer 59

(1-4 days)

Question 60

_{Pediatric Physiology - Transitional Circulation at Birth}

When does the Anatomical Closure of the Ductus Arteriosus happens?

Answer 60

(2-3wks)

Question 61

_{Pediatric Physiology - Transitional Circulation at Birth}

What’s the main physiologic change responsible for the Closure of the Ductus Arteriosus?

Answer 61

↑ PaO2

_{(Which leads to decreased PVR + Decreased in the levels of PEG1)}

Question 62

_{Pediatric Physiology - Fetal Circulation}

Overview of fetal circulation before birth

Answer 62

See picture attached

Question 63

_{Pediatric Physiology - Fetal Circulation}

Overview of infant circulation after birth

Answer 63

See picture attached

Question 64

_{Persistent Fetal Circulation}

What happens if the fetus just after birth and as they become a neonate, fail to convert to the adult circulatory pattern, and remains in Persistent Fetal Circulation?

Answer 64

The infant will remain in persistent fetal circulation

A high PVR is responsible for shunting blood away from the lungs and out the ductus arteriosus

I high PVR causes a high RA backward, which is responsible for shunting blood from the RA to the LA via the foramen ovale

As the alveoli are first exposed to O2 after birth, the PVR decreases, resulting in an increase flow in the adult circulatory pattern and eventual closure of the foramen ovale and the ductus aretriosus

When neither of this happens, the neonate remains in

persistent fetal circulation

There are three main categories of etiologies of persistent fetal circulation that would cause the infant to remain in this circulatory pattern

Question 65

_{Persistent Fetal Circulation}

There are three main categories of etiologies of persistent fetal circulation that would cause the infant to remain in this circulatory pattern

Answer 65

Congenital heart defects

Primary Persistent Fetal Circulation hypertrophy

Secondary Persistent Fetal Circulation

Question 66

_{Persistent Fetal Circulation}

Any congenital heart defect that results in elevated PA or RA pressures will have a Persistent Fetal Circulation in order to

Answer 66

Allow adequate cardiac output

Question 67

_{Persistent Fetal Circulation}

Any congenital heart defect that results in elevated PA or RA pressures will have a Persistent Fetal Circulation. The effect of this will be which type of shunt?

Answer 67

R=>L shunt

The hallmark of at Cyanotic heart defect

Question 68

_{Persistent Fetal Circulation}

PFC characterized by an increase in the muscularization of the walls of the pulmonary vessels, which results in persistently elevated PVR. This is also known as:

Answer 68

Primary Persistent Fetal Circulation hypertrophy

There is a poor prognosis for this etiology

Question 69

_{Persistent Fetal Circulation}

PFC commonly seen in infants with lung disease, where the hypoxia and acidosis lead to pulmonary vasoconstriction and persistently elevated PVR, is aldo known as:

Answer 69

Secondary Persistent Fetal Circulation

Question 70

_{Persistent Fetal Circulation}

Some of the causes of these lung-disease types that would lead to secondary PFCs are:

Answer 70

Meconium aspiration (most common)

Hilum membrane disease

Diaphragmatic hernia

Sepsis syndrome

Pulmonary embolism

Question 71

_{Persistent Fetal Circulation}

In general Persistent Fetal Circulation result from failure of which hemodynamic parameter to decrease after birth?

Answer 71

PVR

Question 72

_{Persistent Fetal Circulation}

Which could be reponsible for PVR failure to decrease after birth?

Answer 72

Hypoxia

Hypercarbia

Acidosis

Hypothermia

The ultimate reason why PVR will remain elevated is failure of PaO2 to rise and the resulting Hypoxia

Question 73

_{Persistent Fetal Circulation}

Besides PVR failing to decrease after birth, what are other general causes of Persistent Fetal Circulation?

Answer 73

Anesthetic changes in peripheral vascular tone

High positive airway pressures

R-L extrapulmonary shunting of blood

The ultimate reason of keeping PVR elevated is failure of PaO2 to rise and the resulting Hypoxia