Paediatric Clinical Chemistry Flashcards
What are clinical issues surrounding low birth weight?
Respiratory distress syndrome (RDS)
Retinopathy of prematurity (ROP)
Intraventricular hemorrhage (IVH)
Patent ductus arteriosus (PDA)
Necrotizing enterocolitis (NEC)
What is NEC?
Inflammation of the bowel wall progressing to necrosis and perforation
Bloody stools
Abdominal distension
What is this?
Intramural air, a sign of NEC
What is the normal development of the nephrons?
Develop from week 6.
Start producing urine from week 10.
Full complement from week 36.
Functional maturity of GFR is not reached until about 2 years of age.
What are defects within renal function and how do these translate clinically?
Low GFR for surface area; consequences are:
- Slow excretion of a solute load
- Limited amount of Na+ available for H+ exchange
Short proximal tubule means there is a lower reabsorptive capability than in the adult although reabsorption is usually adequate for the small filtered load.
Loops of Henle/distal collecting ducts are short and juxtaglomerular giving a reduced concentrating ability with a maximum urine osmolality of 700 mmol/kg.
Distal tubule is relatively unresponsive to aldosterone which leads to a persistent loss of sodium of c.1.8 mmol/kg/day.
What are causes of electrolyte disturbances?
High insensible water loss:
- High surface area
- High metabolic/respiratory rate
- High transepidermal fluid loss
Drugs:
- Bicarbonate (for acidosis)
- Antibiotics
- Caffeine/theophylline (for apnoea)
- Indomethacin (for PDA)
- Growth (or rather a lack of it)
What is hypernatraemia in children?
Hypernatraemia after 2 weeks of age is uncommon and is usually associated with dehydration.
Salt poisoning and osmoregulatory dysfunction are rare but should be considered in cases of repeated hypernatraemia without obvious cause.
Routine measurement of urea, creatinine and electrolytes on paired urine and plasma on admission may differentiate these rare causes.
What are causes of hyponatraemia?
Congenital adrenal hyperplasia (1in 15000)
What are signs and symptoms of congenital adrenal hyperplasia?
Hyponatraemia/hyperkalaemia with marked volume depletion
Hypoglycaemia
Ambiguous genitalia in female neonates
Growth acceleration (in child)
What is hyperbilirubinaemia?
High level of synthesis (RBC breakdown)
Low rate of transport into liver
Enhanced enterohepatic circulation
What is Kernicterus?
1g/l albumin binds 10 micromol/l bilirubin
Average albumin at term 34 g/l (lower in prem)
Free bilirubin crosses the blood brain barrier and causes Kernicterus (bilirubin encephalopathy)
What are causes of hyperbilirubinaemia?
Haemolytic disease (ABO, rhesus etc)
G6PD deficiency
Crigler-Najjar syndrome
What is prolonged jaundice?
Prolonged jaundice is jaundice that lasts for more than 14 days in term babies and more than 21 days in preterm babies.
What are causes of prolonged jaundice?
Prenatal infection/sepsis/hepatitis
Hypothyroidism
Breast milk jaundice
What are causes of conjugated hyperbilirubinaemia?
Conjugated/direct bilirubin >20 mmol/l is always pathological.
Biliary atresia, choledocal cyst
- 1/17,000 UK
- 20% associated with cardiac malformations, polysplenia, sinus inversus
- Early surgery essential
Ascending cholangitis in TPN: Related to lipid content.
