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FHB I - Cardiac Unit > Neonatal Circulation > Flashcards

Flashcards in Neonatal Circulation Deck (10):

How do atria pressures change:

What does clamping the umbilical vein result in?

What does this lead to?

decreased pressure in right ventricle

decreased pressure in pulmonary circuit allows easier flow into lungs (bc starting to breathe)

increased pulmonary flow= increased LA pressures

septum primum closes, -allows for separation between 2 chambers, atrial chambers are separated

Uterine contractions and eventual cord clamping causes a decrease in pressure in the umbilical vein and therefore the right atrium.
Clamping the umbilical arteries raises the systemic vascular resistance causing increased left sided pressures, translated to increased left atrial pressures.


How do pressures change in ductus arteriosus?

Increased SVR (systemic vascular resistance) secondary to crying, moving, and clamping the umbilical arteries.

decreased PVR secondary to opening of the lungs

reversal of flow in ductus arteriosus


(pulmonary vascular resistance drops bc you’ve opened lungs. less pressure here, more pressure in aorta
bradykinin-facilitates closure of ductus arteriosus and allows blood to not keep flowing across ductus arteriosus )

Increased systemic pressures (crying, moving, no placenta) cause decreased flow across the ductus arteriosus.
Bradykinin produced in newly functional lungs cause closure of the ductus arteriosus

(gradient to flow starts to diminish. then closes off. in utero- R sided pressures higher than L sided pressures. when pressures start to increase, over here they decrease. murmur you hear as ductus arterioles starts to close. eventually more pressure here, less there then starts to shrink and eventually becomes ligamentus-arteriosus. )


What is the only valve that shuts? (hole that closes)

foramen ovale

Slide 41

this combination (decrease in pressure in the umbilical vein and therefore the RA/increased pressure in umbilical arteries raising the systemic vascular resistance) causes increased left sided pressures, decreased flow across foramen oval and presses the septum primun against the septum secundum, thereby closing the foramen ovale

Decreased pulmonary vascular resistance allows easier passage of blood from the right ventricle into the pulmonary vasculature.
This increases flow to the left atrium which further increases pressure and facilitates closure of the foramen ovale.


Which pipes close?

ductus venosus
ductus arteriosus

ductus venosus becomes ligamentum-venosus
ductus arteriosus-ligamentum arteriosus


Draw Oxygen dissociation curve. PO2 against O2 Hb saturation.

How will a shift to the right affect affinity and unloading? What causes a shift to R?

How will a shift to the left affect affinity and unloading? What causes shift to L?

Slide 43.

Shift to R: decreased affinity, increased unloading (think about metabolic activity..things that increase metabolic activity- increased 2,3 DPG, hypoxia, acidosis (decreased pH) increased temperature)

Shift to L increased affinity, decreased unloading
(-decreased 2,3 DPG (or less influence i.e. Hgb F), increased PaO2, increased pH, decreased temperature)


How will HbF shift the curve?
HgA? Why?

HbF- shift to L
HgA- shift to R

Adult Hemoglobin: (HbA)
2 alpha and 2 beta chains

Fetal Hemoglobin: (HbF)
2 alpha and 2 gamma chains

2,3-DPG binds to deoxy-HbA between beta chains and stabilizes in the deoxy- form. This means a lower O2 affinity/ increased unloading.

The gamma chains of HbF allow less 2,3-DPG binding. Therefore, HbF has a higher O2 affinity/ decreased unloading in the presence of 2,3-DPG than HbA.

fetal hemoglobin not responsive to DPG important. higher O affinity bc doesn't respond to DPG


If mother's concentration of PO2 is at 35mmHg, how saturated will a fetal hemoglobin molecule be?

shift to L, 80 percent saturated
bind O at lower partial pressures of O.


What would happen if the ductus arteriosus didn't close and the baby was born and pulmonary pressure dropped? How do you correct this?

then higher pressure in aorta than pulmonary circuit. so blood goes from aorta into pulmonary circuit again. problem is lungs weren’t designed for that extra flow. so increase hydrostatic pressure in vessels in lungs. leaking. get pulmonary edema. too much and cant oxygenate blood when comes to lungs. must be stopped. incision… put clamp on ductus arteriosus. give medicines that facilitate closure as well… for most part rel. simple thing to correct

if lung pressure high and all these circuits are still open… yet outside of mom.. too much pressure inside pulmonary artery (too much pressure in RV..too much pressure in RA. pressure in RA high then blood shunts to LA. if pressure too high in lungs and too high in pulmonary artery that blood goes through ductus arteriosus as well. so have deoxygenated blood that comes to periphery. so baby moving, shouldn't peripheral pressures higher than pulmonary? well maybe. if deliver de-oxygenated blood to muscles, how does body make ATP? anareobic metabolism…H ions..peripheral vasodilation. dilated capillary beds. systemic pressure falling off. deoxygenated blood into body. blood that does make it to lungs… will be normal. but measure in foot it’ll be off… so look at gradients -is there more than a 10 percent saturation between hand and L arm or somewhere in leg. pre-ductal vs post-ductal …post ductal- stuff mixed from coming from ductus arteriosus. pre-ductal- only stuff that went to lungs and went to head or R side or R arm.
how to fix? … drop lung pressure. use NO sometimes to open up lungs. oxygenation in general. too high O not good either - problems w retina…. O, NO and put on ventilatior. cirfactant if lungs haven't opened.


At P 50 in adult, what is PO2 and O2 Hb saturation? Fetus?

At p50-spot at which 50 percent of hemoglobin saturated w oxygen is about 27 PO2 oxygen (xaxis)
if uterus has PaO2 of 35 … adult saturated about 62 percent hemoglobin bound w Oxygen. shift to L…now O saturation over 80.


Describe difference in O saturation curve from prenatally to after birth.

PaO2 ~35 mmHg (best case)
You need the shift to the left! Hb needs to bring as much O2 as possible to the fetal tissues. The relative hypoxic/ anaerobic environment of the fetus would allow DPG to make Hg less O2 avid.

After birth,
Increased PaO2 (from High PAO2).
Time to move to the right. It is less important to “grab” the O2 as it is to deliver it to he tissues. Hence the action and benefits of DPG.

Transition to HbA
Greater effect of 2,3-DPG