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Anesthesia Concepts 4 (Butera) > Fetal Circulation > Flashcards

Fetal Circulation Flashcards

1
Q

Placenta function

A

provides gas exchange in the fetus

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2
Q

What are the vessels of the placenta?

A

2 umbilical arteries- deoxygenated blood from fetus to placenta

1 umbilical vein- returns oxygenated blood from placenta back to fetus

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3
Q

What are the three main fetal shunts?

A

Ductus Arteriosus
Foramen Ovale
Ductus Venosus

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4
Q

Fetal circulation changes at birth due to ____

A

loss of placenta as a source and establishment of lungs as the gas exchange unit

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5
Q

Parallel Circulation

A

Fetal Circulation shunts blood away from lungs
Both ventricles supply the systemic circulation

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6
Q

10-15% of blood from PA passes through ____

A

the lungs to reach LA, but the rest (90%) is shunted to to distal Ao via DA (the 10% which goes through lung goes back to LA via Pulmonary vein to LV to Ao to abdomen and lower extremities) then to internal iliac arteries, to 2 umbilical arteries then to placenta

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7
Q

Coming from placenta to 1 umbilical vein, 50% of blood to the IVC via ____

A

ductus venosus (DV connects L PV, to L HV), 50% through hepatic sinus to liver and enters IVC via HV

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8
Q

IVC blood enter LA during what percent of the cardiac cycle?

A

IVC blood enter LA during 80% of cardiac cycle. In 20% blood from IVC crosses TV into RV

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9
Q

Deoxygenated blood from head, neck, and upper extremities coming through SVC also ____

A

crosses tricuspid valve into RV

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10
Q

Most of the blood goes to which 3 large branches of aorta?

A

(brachiocephalic, left common carotid, and L subclavian to head, neck, UE. Preferential flow to coronary and cerebral circulation.

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11
Q

fetal lungs = ____
placenta = site of ____

A

Fetal lungs are collapsed
Placenta is sight of gaseous exchange

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12
Q

fetal hemoglobin

A

Fetal hemaglobin (HbF) – higher oxygen affinity – 2 𝛼 and 2 𝛾 globin chains
Although, Fetal Hgb has higher affinity for oxygen in such a low partial pressure environment of the fetal tissue it also readily unloads oxygen.

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13
Q

adult vs. fetal oxyhemoglobin dissociation curve

A
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14
Q

Hemodynamics and Oxygen Saturations of Term Fetus

A

Low O2 saturation in SVC
Higher O2 saturation in IVC
Patent ductus arteriosus (DA), foramen ovale (FO)
Collapsed lungs
High PVR

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15
Q

Hemodynamics and Oxygen Saturations during Transitional Circulation

A

DA and FO closing
Lower PVR
Increased AO O2 saturation

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16
Q

What closes several days after birth?

A

DA and FO closed

17
Q

Ductus Arteriosus

A

Organ Bypassed: lungs
Changes after Birth: closure
Adult Remanent: Ligamentum Arteriosum

18
Q

Foramen Ovale

A

Organ Bypassed: lungs
Changes after Birth: closure
Adult Remanent: Fossa Ovalis

19
Q

Ductus Venosus

A

Organ Bypassed: liver
Changes after Birth: closure
Adult Remanent: Ligamentum Venosum

20
Q

Umbilical Arteries

A

Changes after Birth: Obliteration
Adult Remanent: Medial Umbilical Ligaments

21
Q

Umbilical Vein

A

Changes after Birth: Obliteration
Adult Remanent: Ligamentum Teres Hepatis

22
Q

Foramen Ovale creates what kind of shunt? How?

A

Creates a R to L shunt in utero

The stream of blood from ductus venosus (DV) has higher velocity in IVC than the stream from the lower body and hepatic veins.
Facilitates delivery of higher oxygenated content blood across foramen ovale (FO) to Left atrium (LA) to LV then to 3 large branches of aorta

23
Q

Describe the closure of the foramen ovale

A

In utero RAP> LAP
Inc in LAP causes closure of FO
Functional closure usually progresses to anatomical closure
May be patent in 30% of adults
May be patent in 50 % of children < 5 yrs old

24
Q

Ductus Arteriosus creates what kind of shunt? How?

A

R to L shunt

90% of blood from Pulmonary artery shunted to distal Aorta via DA
In utero, patency by high levels of prostaglandins (prostacyclin (PGI2) and prostaglandin E1 (PGE1) due to the response to low oxygen tension relevant to hypoxia.

25
Q

Describe the closure of the Ductus Arteriosus

A

Contraction of smooth muscle
Occurs within first day of life
↑Partial pressure of oxygen (PO2) and ↓ prostaglandins
Oxygen is dose-dependent ductal constrictor
NE and Epi may also have effect
Permanent Anatomical Closure
2-3 weeks of life in normal full-term neonate

26
Q

Ductus Venosus provides _____

A

oxygenated blood from umbilical vein to bypass liver to IVC

50% of UV blood bypasses liver

27
Q

Describe the closure of the Ductus Venosus

A

High oxygen tension which occurs after birth causes umbilical vessel constriction
Passive closure results from decrease in umbilical venous blood flow due to the severed connection between umbilical cord to placenta after birth
High levels of NE may also cause vasoconstriction
Functional closure by 1 week of life
Anatomic closure by 3 months

28
Q

Fetal pulmonary vascular features

A

Low pulm BF secondary to high pulmonary vascular resistance (PVR)
Vasoconstriction
↓ PaO2
↓pH, leukotrienes

29
Q

Potent Vasodilators of fetal pulmonary vessels

A

Ach, histamine, bradykinin, PGE1, PGE2, PGI2, prostaglandin D2, 𝛽 Adrenergic catecholamines (NE & Epi)

30
Q

After Birth, _____ commences. Then what happens?

A

After Birth- ventilation commences

Reduced mechanical compression of small pulmonary vessels
↑bradykinin levels
↑PaO2  ↓PVR
↓PGE2 and prostacyclin levels
Consequently, ↑ in pulm BF to lungs results in ↑ pulmonary venous return to LA so ↑ in LV output and aorta receives more blood resulting in ↑ aortic BP

31
Q

Myocardial Performance in Neonate

A

In utero
RV has CO of about 330 mL/kg/min
LV has CO of about 170 mL/kg/min

At Birth- Newborn
RV and LV CO is about 350 mL/kg/min

By 8-10 weeks of life
CO is about 150 mL/kg/min

32
Q

How is myocardial performance different in Neonates?

A

Limited Preload Reserve
- Augmentation of stroke volume via Frank-Starling mechanism is limited compared to adult

Reduced Contractile Capacity
- Neonatal cardiac cells contain more water and fewer contractile elements than mature myocardium

Reduced Ventricular Compliance
-Deficiency of elastic elements

Incomplete autonomic innervation
- Sympathetic innervation is underdeveloped
- Parasympathetic, however, is fully functional at birth

Immature Myocardial metabolism
May be protective

33
Q

Oxygen Consumption (infant, child, adult)

A

Infant: 6-8 mL/kg/min
Child: 4-6 mL/kg/min
Adult: 2-3 mL/kg/min

34
Q

Cardiac Output (neonate, infant, adult)

A

Neonate: 350 mL/kg/min
Infant: 150 mL/kg/min
Adult: 75 mL/kg/min

35
Q

Blood Volume for different age groups

A

Premature: 90-100 mL/kg
Newborn (<1 month): 80-90 mL/kg
Infants (3 mo to 3 yrs): 75-80 mL/kg
Children older than 6 yrs: 65-70 mL/kg
Adults: 65-70 mL/kg

Anesthesia Concepts 4 (Butera) (15 decks)

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