Neonates - Physiology

Question 1

Describe the passage of oxygenated blood in a foetus?

Answer 1

Placenta –> Umbilical Vein –> Ductus Venosus (through liver) –> IVC

Question 2

The foetal lungs aren’t functional, how does a foetus get oxygenated blood from the right heart to the left?

Answer 2

Bypasses the pulm circulation by 2 shunts:

• Foramen Ovale (atria)
• Ductus Arteriosus (PA to Aorta)

Question 3

Where does a foetal O2 sat sit?

Answer 3

60-70%

Question 4

Newborns lack shivering thermogenesis, how do they resist cold?

Answer 4

Use of brown fat
Cold Stress –> Lipolysis –> Heat generation

(A sympathetic process)

Question 5

Physiological jaundice occurs around 2/3 days up to 7-10. What do we do if the bilirubin is high enough to cause problems?

Answer 5

Blue Light Phototherapy

Exchange Transfusion

Question 6

It’s quite normal for a newborn to lose up to 10% of its weight, why is this?

Answer 6

Fluid moves from interstitium to intravascular and triggers diuresis

Question 7

why can’t premature babies regulate their fluids properly?

Answer 7

Less Fat
More loss through kidney
More insensible loss (immature skin/lungs)

Question 8

How does physiological anaemia come about in newborns

Answer 8

Produce much less RBCs after birth –> anaemia in the first few weeks before erthropoieting production steps up

Most common cause of anaemia is iatrogenic blood letting (e.g. taking blood samples from a septic baby)