Inborn errors of metabolism: Difference between revisions
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Revision as of 17:03, 19 October 2016
Background
- Suspect in any sick neonate
- Newborn screening varies by state
- May present as late as early childhood
- Clinical manifestations are due to accumulation of toxic metabolites
- Must rule-out sepsis (more common in these patients)
Clinical Features
Exam and history:
- Lethargic (secondary to hyperammonia encephelopathy)
- Nausea/vomiting
- Difficulty feeding
- Seizure
- Unusual odors
- Hypotonia
- Encephalopathy
- Hypoglycemia
- Hepatic dysfunction
Differential Diagnosis
Sick Neonate
THE MISFITS [1]
- Trauma
- Heart
- Congenital heart disease
- Hypovolemia
- Endocrine
- Metabolic
- Sodium
- Calcium
- Glucose
- Inborn errors of metabolism
- Seizure
- Formula / feeding problems
- Intestinal Disasters
- Toxin
- Sepsis
Evaluation
- Glucose level
- Ammonia
- Should be <200 in normal neonate (higher suggests urea cycle disorders)
- Lactate
- Chemistry
- Anion gap associated organic acidemias
- May see hypoglycemia, metabolic acidosis
- Urinalysis (ketones)
- LFT
- VBG
Management
Must stop catabolism and acculmulation of toxins/ammonia
- Keep NPO
- Removes potential inciting metabolic substrates
- IVF
- Normal saline 20 mL/kg boluses
- Once rehydrated, switch to IVF with dextrose (D10) at 1-2x maintenance
- Increases renal excretion of toxic metabolites
- Hyperammonemia
- <500
- (Na phenylacetate & Na benzoate) 250mg/kg in D10 over 90min; then 250mg/kg/d infusion
- Arginine 210mg/kg IV/IO in D10 over 90min; then 210mg/kg/d infusion
- >500
- Dialysis
- <500
- NaBicarb if acidotic
Cerebral edema
- Hyperammonemia is risk factor
- Give mannitol 0.5gm/kg IV/IO
- Do not give steroids (worsens hyperammonemia)
If seizing
- consider Vitamin B6 (pyroxidine)
Subsequent Management
- Consider L-carnitine in conjunction with specialist, as some diseases may respond (but has side effects)
See Also
References
- ↑ Brousseau T, Sharieff GQ. Newborn emergencies: the first 30 days of life. Pediatr Clin North Am. 2006 Feb;53(1):69-84, vi.