Pediatric Nutrition and Metabolic Disorders
This domain covers infant feeding, nutritional deficiency and obesity, and the inherited metabolic disorders that present in the newborn period or with acute decompensation.
Infant feeding
- Exclusive breastfeeding for 6 months, with complementary foods from 6 months. Give vitamin D 400 IU/day to all breastfed infants and iron-fortified foods from 6 months.
- Whole cow milk is delayed until 12 months. Estimated energy needs are roughly 100-120 kcal/kg/day in infancy, falling with age.
Nutritional disorders
- Growth faltering is weight below the 2nd percentile or falling across two major centile lines; screen for celiac disease, cystic fibrosis, renal tubular acidosis and congenital heart disease.
- Obesity is BMI at or above the 95th percentile for age and sex.
Inherited metabolic disease
- Phenylketonuria: phenylalanine hydroxylase deficiency, detected on newborn screening, treated with a low-phenylalanine diet; avoid aspartame.
- Galactosemia: GALT deficiency with jaundice, hepatomegaly, cataracts and Escherichia coli sepsis; lactose-free formula is lifesaving.
- Urea cycle defects: hyperammonemia with respiratory alkalosis after protein feeding.
- Organic acidemias: metabolic acidosis with ketosis and secondary hyperammonemia.
- MCAD deficiency: hypoketotic hypoglycemia provoked by fasting.
- Maple syrup urine disease: branched-chain amino acids, sweet odour, neonatal encephalopathy.
Worked example
A 5-day-old presents with poor feeding, vomiting and lethargy. Ammonia is 600 micromol/L and blood gas shows respiratory alkalosis. Reasoning: hyperammonemia with respiratory alkalosis points to a urea cycle defect. Stop all protein, give intravenous glucose, arginine and sodium benzoate, and arrange dialysis for ammonia above 500.
Traps
Checking only glucose in a septic-appearing neonate and never sending ammonia; continuing protein feeds during hyperammonemia; and forgetting that carnitine is depleted in organic acidemias.