The foetal circulation and adaption at Birth

Question 1

Function of placenta?

Answer 1

Fetal homeostasis 
Gas exchange 
Acid base balance 
Nutrient transport to fetus 
Waste product transport from fetus 
Hormone production 
Transport of IgG
Prostaglandin E2

Question 2

How fetal circulation differs from adult circulation? (4)

Answer 2

• Placenta is included in fetus fro - gas exchange, nutrition, waste excretion and homeostasis
• Lungs are fluid filled and unexpanded
• Liver has little role in nutrition and waste management
• Gut is not in use

Question 3

What do the umbilical arteries do?

Answer 3

Take deoxygenated blood to placenta

Question 4

What does umbilical vein do?

Answer 4

Take oxygenated blood from the placenta back to foetus

Question 5

Where does the placenta sit?

Answer 5

End of the umbilical cord

Question 6

What are the 3 shunts specific to foetal life?

Answer 6

Ductus venosus
Foramen Ovale
Ductus arteriosus

Question 7

Where does blood go when returning from the placenta?

Answer 7

Right side of the heart- then distributed to growing foetus

Question 8

Anatomy of the ductus venosus?

Answer 8

Connects the umbilical vein to the inferior vena cava

Question 9

Anatomy of the foreman ovale?

Answer 9

Opening in the atrial septum connecting RA to LA

Question 10

Anatomy of ductus arteriosus?

Answer 10

Connects pulmonary bifurcation to descending aorta

Question 11

What does the ductus venous do?

Answer 11

Carries majority of blood from the placenta into the inferior vena cava bypassing portal circulation (liver)

Question 12

What does the ductus venous do?

Answer 12

Carries majority of blood from the placenta into the inferior vena cava bypassing portal circulation (liver)

Question 13

Function of the foreman ovale?

Answer 13

Allows blood to flow from RA to LA

Allows best oxygenated blood to enter LA then go into LV, to ascending aorta and then carotids

Question 14

What is the foreman ovale physically?

Answer 14

Membrane flap on left atrium side

Question 15

How is the ductus arteriosus kept open?

Answer 15

Circulating prostaglandin E2 produced by the placenta

Question 16

How much of the RV output in a fetus goes to the lungs?

Answer 16

7%

Question 17

Where does majority of the RV output go in a fetus?

Answer 17

Ductus arteriosus to join the descending aorta

Question 18

What happens to a baby in the few minutes following birth?

Answer 18

Baby inflates lung and cries
Goes from blue to pink
Cord is clamped and cut

Question 19

Changes in pulmonary vascular resistance when a baby is born?

Answer 19

Decreases
Breath in- lungs can physically expand
Increased circulating oxygen

Question 20

Changes in systemic vascular resistance when a baby is born?

Answer 20

Increases

Cord clamped and cut

Question 21

General circulation changes when a baby is born?

Answer 21

More of cardiac output goes to lungs

Question 22

How does the foreman ovale close?

Answer 22

As PVR falls and SVR rises- the left atriall pressure exceeds the right atrial pressure

• Flap is pushed closed
• Once the cord has been clamped the pressure in the left side becomes higher than the pressure in the right

Question 23

Explain duct constriction?

Answer 23

Decreased PVR cause a decrease in flow
Decreased circulating PGE2 due to increased lung metabolism
Increased PO2= oxygen sensitive muscular layer
Shunt becomes bidirectional than left to right
Physiologically it closes withing first 24 hours, anatomically closes withing 7-10 days

Question 24

In what types of patients is a patent ductus arteriosus common?

Answer 24

Preterm infants

Question 25

Treatment options for failure of duct closure?

Answer 25

Wait and see
Surgery
NSAIDS (Nonsteroidal anti-inflammatory drugs)

Question 26

What can be used to keep a duct open?

Answer 26

PGE2
Prostaglandin E2
Until an alternative shunt is established or a definitive surgery carried out

Question 27

Duct dependent circulation?

Answer 27

Some congenital heart diseases cause this where the duct must be kept open with PGE2

Question 28

What happens to pulmonary resistance when a baby is born?

Answer 28

Continues to drop until it reaches adult level about 2-3 months later

Question 29

When is persistent pulmonary hypertension of the newborn more likely?

Answer 29

Sick babies-
Sepsis 
Hypoxic ischaemic insult 
Meconium aspiration syndrome 
Cold stress 

Can be related to underlying anatomical abnormality = congenital diaphragmatic hernia

Question 30

When does PPHN occur?

Answer 30

Lung vascular resistance fails to fall after birth

Question 31

Anatomically and physiologically what happens in PPHN?

Answer 31

Shunts remain - R-L blood flow in PFO and PDA

Large difference between pre and post ductal oxygen saturation

Question 32

Signs of PPHN?

Answer 32

Blue baby

Question 33

What does PPHN mean?

Answer 33

persistent pulmonary hypertension of the newborn

Question 34

Treatment for PPHN?

Answer 34

Ventilation
Oxygenation 
High systemic blood pressure - more difficult for blood to go from left to right 
Inhaled nitric oxide 
ECLS- extracorporeal life support

Question 35

What is important in congenital heart disease

Answer 35

Ductus arteriosus

Question 36

How we treat PPHN?

Answer 36

2 Aims- reduce PVR, increase SVR

Question 37

How we increase SVR when treating HHPN?

Answer 37

Oxygen
Ventilation 
Sedation 
Thermoregulation 
Correction of acidosis 
Treatment of sepsis 
Inhaled NO

Question 38

How we reduce PVR? Peripheral when treating HHPN?

Answer 38

Maintain higher than adequate BP
Inotropes Support other organ function
In severe cases ECLS