Chemical Pathology 21 - Paediatric clinical chemistry Flashcards
(33 cards)
What is retinopathy of prematurity?
abnormal growth of blood vessels in eye → vision loss
What is NEC?
Inflammation of bowel wall → necrosis and perforation
Symptoms = bloody stools, abdominal distension, intramural air
When do nephrons start to
- develop
- produce urine
- full complement
- reach functional maturity of GFR
- week 6
- week 10
- week 36
- 2 years
How is a baby’s glomerulus different to an adult’s?
large SA:V (relatively low GFR for their surface area) →
- Slow excretion of solute load
- Limited amount of Na+ available for H+ exchange
How is a baby’s proximal convoluted tubule different to an adult’s?
short PCT → lower resorptive capability
- BUT renal threshold for glycosuria much lower in neonates - glycosuria appears at a lower plasma glucose level in neonates
- Reabsorption of bicarbonate also not as effective (→ neonates’ propensity to acidosis)
How is a baby’s Loop of Henle/distal convoluted tubule different to an adult’s?
short → ↓ concentration ability
How do Na and K levels compare in neonates vs adults?
- DCT less responsive to aldosterone > persistent loss of Na (1.8 mmol/kg/day)
- ↓ K excretion → higher upper limit of normal K in neonates (6 vs 5.5)
why do babies lose weight in the first week of life?
In utero - babies have more ECF than adults
Birth - ↓ pulmonary resistance → ANP release → redistribution of fluid
What % weight loss is acceptable for babies in their first week of life?
10%
Why do babies require more fluids than adults?
High insensible water loss
- ↑ surface area
- ↑ skin blood flow
- ↑ metabolic/respiratory rate
- ↑ transepidermal fluid loss (skin not keratinised in premature infants)
Drugs
- Bicarbonate (for acidosis) → **↑ Na content
- Antibiotics ↑ Na content (sodium salts)
- Caffeine/theophylline (for apnoea) → renal Na loss
- Indomethacin (for PDA) → oliguria
Why might there be hypernatraemia in a baby >2w?
Hypernatraemia >2 weeks of age uncommon - usually associated with dehydration
What are some potential causes for repeated hypernatraemia in babies?
Salt poisoning
Osmoregulatory dysfunction
Recall a cause for hyponatraemia in babies
Congenital Adrenal Hyperplasia (CAH)
Recall the pathophysiology of CAH
21-hydroxylase (21-OH) deficiency → ↓ cortisol / aldosterone → salt loss → hyponatraemia
↓ 21-OH → ↑ precursors 17-OH progesterone + 17-OH pregnenolone → ↑androgens
Recall the clinical features for CAH
- Hyponatraemia/hyperkalaemia with volume depletion (lack of aldosterone) → salt-losing crisis
- Hypoglycaemia (lack of cortisol)
- Ambiguous genitalia in female neonates (not obvious in male neonates – present with salt-losing crisis)
- Growth acceleration
What happens to Hb after birth?
↓Hb as you start making HbA
Reasons for Neonatal Hyperbilirubinaemia
unconjugated hyperbilirubinaemia
↑ bilirubin synthesis
↓ rate of transport into the liver
Enhanced enterohepatic circulation
What complication may arise from excess bilirubin in the neonate?
Unbound, free bilirubin crosses BBB → kernicterus (bilirubin encephalopathy)
Which protein binds bilirubin?
albumin
What is the bilirubin treatment level for phototherapy?
term
350 total serum BR micromol/L
prem
120 total serum BR micromol/L
What is the bilirubin treatment level for exchange transfusion?
term
450 total serum BR micromol/L
prem
230 total serum BR micromol/L
Why is there a lower treatment threshold level in premature infants?
because albumin is lower, and BBB is leakier
define prolonged jaundice
>14 days in term babies
>21 days in pre-term babies
Causes of prolonged jaundice
Prenatal infection/sepsis/hepatitis
Hypothyroidism (screened at day 6-8)
Breast milk jaundice
