Chem path 7s - Paediatric clinical chemistry

Question 1

What is the earliest gestation which you’d deliver a child?

Answer 1

24 weeks

Question 2

What are some problems commonly seen in premature babies?

Answer 2

RDS
Retinopathy of prematurity
IVH
PDA
NEC

Question 3

What are the features of NEC?

Answer 3

Bloody stools
Abdominal distension
Intramural air (pneumatosis intestinalis)

Question 4

At what gestation do nephrons develop?

Answer 4

6 weeks (full complement of nephrons by 36 weeks)

Question 5

What gestation do nephrons start producing urine?

Answer 5

10 weeks

Question 6

At what age is functional maturity of GFR reached?

Answer 6

2 years

Question 7

Baby kidney anatomy: glomerulus

Answer 7

Large SA: vol ratio therefore relatively low GFR for their SA –> slow excretion of solute load
Limited amount of Na+ available for H+ exchange so more susceptible to acidosis

Question 8

What are two reasons why neonates are more prone to acidosis?

Answer 8

Limited Na+ available for H+ exchange + reabsorption of bicarbonate is not as effective

Question 9

Proximal convoluted tubule in neonates

Answer 9

Shorter than adults therefore lower resorptive capability and therefore renal threshold for glycosuria is lower

Question 10

Loop of Henle/DCT in neonates

Answer 10

Shorter and thus reduced concentrating ability. DCT relatively unresponsive to aldosterone so constantly losing sodium and reduced K+ excretion

Question 11

What is the upper limit of normal for K+ in neonates?

Answer 11

6.0mmol/L (compared to 5.5. in adults)

Question 12

How much weight can babies lose in the 1st week of life and be normal?

Answer 12

10% loss of their body weight in 1st week is considered normal

Question 13

How mcuh more water do neonates need per day than adults?

Answer 13

6x more

Question 14

Na+ and K+ requirementes in neonates vs adults

Answer 14

Higher

Question 15

Causes of high insensible water loss in neonates

Answer 15

High SA:volume ratio
Increased resp/metabolic rate
High skin blood flow
High transepidermal fluid loss (skin is not fully keratinised in preterm neonates)

Question 16

When is hypernatraemia normal in neonates?

Answer 16

Normal in first 2 weeks, suggests dehydration after 2 weeks

Question 17

Most common cause of hyponatraemia in neonates

Answer 17

CAH - 21-Hydroxylase deficiency

Question 18

In a prem baby, why are the thresholds to treat hyperbilirubinaemia lower?

Answer 18

They have less albumin and a leakier BBB

Question 19

What is NICE’s definition of prolonged jaundice?

Answer 19

Jaundice >14 days in a term baby or >21 days in prem baby

Question 20

a conjugated bilirubin level above what threshold is always pathological in neonates?

Answer 20

> 20umol/L

Question 21

What are some causes of raised conjugated bilirubin?

Answer 21

Biliary atresia
Choledochal cyst
Ascending cholangitis from TPN, inherited metabolic diseases

Question 22

Which 4 inherited metabolic diseases cause a conjugated hyperbilirubinaemia?

Answer 22

Galactosaemia
Alpha-1-antitryptase deficiency
Tyrosinaemia 1
Peroxisomal diseases

Question 23

Investigations in galactosaemia

Answer 23

RBC Gal-1- PUT

Question 24

Investigations in alpha-1-antitryptase deficiency

Answer 24

Alpha-1-antitryptase

Question 25

Investigations in tyrosinaemia 1

Answer 25

Plasma amino acids

Question 26

Investigations in peroxisomal diseases

Answer 26

Very long chain fatty acid profile

Question 27

Calcium level in a prem vs term baby

Answer 27

Lower in prem

Question 28

Phosphate level in babies vs adults

Answer 28

Higher as babies better at reabsorbing phosphate

Question 29

What are the radiographic features of osteopaenia of prematurity?

Answer 29

Fraying, splaying and cupping of long bones

Question 30

What is the biochemistry in osteopaenia of prematurity?

Answer 30

Calcium normal
Phosphate <1 mmol/L
ALP >12,000 (10X adult ULN)
Vitamin D (Rarely measured)

Question 31

Management of osteopaenia of prematurity

Answer 31

Phosphate/calcium (Can’t give at same time)

1-alpha-calcidol

Question 32

Name the 3 genetic causes of rickets

Answer 32

Pseudo-vitamin D deficiency I
Pseudo-vit D deficiency II
Familial hypophosphataemia

Question 33

Difference between pseudo-vit D deficiency I and II

Answer 33

Type I = Renal hydroxylation defect

Type II = receptor defect

Question 34

Management of pseudo vit D deficiency I and II

Answer 34

1,25- OH vitamin D (calcitriol)