Paediatric Clinical Chemistry Flashcards
Which infants are most at risk?
Babies who weigh <1000g are likely to be born before around 30-weeks’ gestation
What are common problems in infants with LBW?
Respiratory distress syndrome (RDS)
- Common before 34th week of pregnancy
- Lack the surfactant protein in the lungs
Retinopathy of prematurity (ROP)
- An abnormal growth of blood vessels in the eye –> vision loss
Intraventricular haemorrhage (IVH)
Patent ductus arteriosus (PDA)
Necrotising enterocolitis (NEC)
- Inflammation of the bowel wall –> necrosis and perforation
- Symptoms = bloody stools, abdominal distension, intramural air
What is the timeline for nephron developement?
Nephrons start to develop from week 6 –> produce urine from week 10 –> full complement from week 36
Functional maturity of GFR is not reached until 2 years of age
Why are babies susceptible to acidosis?
Low GFR for surface area
Cannot exchange H+ at an appropriate level
Why is the renal threshold for glycosuria lower in neonates?
Short proximal tubule
Lower reabsorptive capability
Why do neonates have a persistent loss of sodium?
Distal tubule are relatively unresponsive to aldosterone
Leads to reduces potential potassium excretion (6.0mmol/L is upper limit for neonates)
Why do all babies lose weight in the first week of life?
Redistribution of water
In utero greater ECF
After birth pulmonary resistance goes down –> release of ANP –> redistribution of the fluid
Roughly 40 ml/kg is normal in a term baby (higher (100 ml/kg) in a preterm baby)
Babies can lose up to 10% of their birth weight in the first week of life and this is not a problem
Summarise the differences in neonatal kidneys
Low GFR for their surface area –> slow excretion
Short proximal tubule –> lower resorptive capability + reduced reabsorption of bicarbonate
LoH and distal collecting ducts are short and juxtaglomerular –> reduced concentrating ability
DCT unresponsive to aldosterone –> persistent sodium loss (and K+ retention)
Why are neonates prone to electrolyte disturbances?
High insensible water loss
Drugs
Growth (give large amounts of feed, Na, for growth)
What causes high water losses in neonates?
High surface area
High skin blood flow
High metabolic/respiratory rate
High transepidermal fluid loss (skin is not keratinised in premature infants)
What is congenital adrenal hyperplasia?
Most common cause is 21-hydroxylase (21-OH) deficiency –> reduced cortisol / aldosterone –> salt loss
The lack of 21-OH –> accumulation of 17-OH progesterone and 17-OH pregnenolone
These then go on to produce high levels of androgens
What are clinical features of congential adrenal hyperplasia?
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
Why do neonates get hyperbilirubinaemia?
High level of bilirubin synthesis
Low rate of transport into the liver
Enhanced enterohepatic circulation
Will be unconjugated
What is bilirubin encephalopathy (Kernicterus)?
1g/L of albumin binds 10micromol/L of bilirubin
Average albumin at term is 34g/L (lower in prematurity)
Albumin in a term baby can bind about 340micromol/L
Rest (free bilirubin) crosses BBB
What are some pathological causes of hyperbilirubinaemia in neonates?
Haemolytic disease (ABO, rhesus, etc.)
G-6-PD Deficiency
Crigler-Najjar syndrome (deficiency of conjugation)
