Paediatric Clinical Chemistry

Question 1

What is the average birth weight for a male child in the UK?

Answer 1

3.3kg

Question 2

How is renal function in neonaes different to an adult?

What are the effects on
1. Acid-base handline
2. elecgtrolytes
3. concentration
4. Glucose threshold?

Answer 2

Lower number of glomeruli –> lower GFR –> less exretion of H+ and lower sodium avaiable of exchange

1. more predisposition to acidosis
2. Lower renal threshold for glycosuria –> glycosiuria from 7mmol/L glocose
3. reduced concentrating ability –> can’t fully concentrate –> higher osmolality
4. higher loss or urinary sodium (due to needed mauration of RAAS) –> reduced potential potassium excretion

Question 3

Babys have a very high water need (would equate to 12.6L in a 70kg adul) - why?

Answer 3

Overall high waer loss
1. Skin: higher surface are, skin blood flow, meabolic/resp rate, transepidermal skins)
2. Drugs: high Na conten , higher renal sodium loss

Question 4

What metabolic disorder is associated with Hyponatraemia in the newborn?

Why?

Answer 4

Congenital adrenal hyperplasia, due due Aldosterone deficiency

Usually aldosterone stimmulates Na+ reabsornbtion and K+ and H+ excretion

Question 5

What is the most common enzyme deficiency in congenital adrenal hyperplasia?

What is the result of that?

Answer 5

Most commonly: 21 hydroxylase deficiency

Leads to : Cortisol + aldosterone deficiency (electrolyte disturbances)

Clinically
Ambigous genitalia in female neonates + growth acceleration

Deficiency leads to built up of precursors –> progesterone that can be converted to Androgens

Question 6

How do calcium and phosphate levels different in neonates than in Adults?

Answer 6

calcium: NR lower than in adults (also needed to kickstart PTH)

Phosphate: higher