Case: Last week we talked about Jane, an otherwise healthy 2-week old girl. Let’s change the story a bit to hit on another consideration in infants. Instead of simply being febrile and fussy, let’s say that she comes back to the ED, this time afebrile, but lethargic with poor cap refill. How does our differential change now?

 

 

Image Credit: Pixabay

What are the important diagnostic considerations for neonates and infants who present very ill?

  1. Infection
  2. Metabolic/Endocrinologic
  3. Trauma
  4. Cardiac
  5. Surgical emergencies

For those of you who like acronyms, consider “THE MISFITS” in neonates and young children presenting with undifferentiated shock (adapted from post on PEM Playbook)

  • Trauma
  • Heart Disease/Hypovolemia
  • Endocrine Emergencies
  • Metabolic
  • Inborn errors of metabolism (to get this acronym to work, there may be some repetition)
  • Seizures
  • Formula problems (think too little or too much water)
  • Intestinal disasters
  • Toxins
  • Sepsis (while this is last, all very sick infants/children should be evaluated/treated for sepsis)

 

Today we will focus on the emergency management of inborn errors of metabolism (IEM), specifically at the immediate recognition and management.

 

 

Epidemiology and Etiology

IEMs are Individually rare, but more common in aggregate- 1/5000 live births for any IEM (Ewing, 2009)

Helpful to lump metabolic deficiencies into 3 broad categories (Saudabray, 2002)

  1. Disorders leading to intoxication (think urea cycle defects)
  2. Disorders involving energy metabolism (think hypoglycemia)
  3. Errors involving synthesis or catabolism of complex molecules (e.g. lysosomal storage disorders)
    • Note: Disorders in this category are rarely treatable in emergency

How do these children present?

  • Deterioration of consciousness is one of the more common presentations of IEMs (El-Hattab, 2015)
    • Other presenting features include vomiting, seizures, apnea, hepatic failure, and cardiac disease (heart failure, cardiomyopathy, arrhythmias)
  • Specific Presentation Patterns (Ewing, 2009)
    • Hypovolemia, hyponatremia, hyperkalemia: Consider adrenal insufficiency
    • Metabolic acidosis, hyperammonemia, ketotic hypoglycemia: Consider an organic acid defect
    • Encephalopathy, respiratory alkalosis, hyperammonemia: Consider a urea cycle disorder
  • Remember, “As the neonate has an apparently limited repertoire  of responses to severe overwhelming illness, the predominant clinical signs and symptoms can be nonspecific like poor feeding, lethargy, failure to thrive, etc.” (Saudabray, 2002)

What is the immediate workup? (El-Hattab, 2015)

Image Credit: Pixabay

  • Primary Workup

    • Glucose
    • Blood Gas with Lactate
    • Serum Chemistry (including BUN/SCr)
    • Urinalysis
    • Complete Blood Count (CBC) and Differential
  • Secondary Workup

    • Specific Findings from Initial Workup and/or Exam
      • Hypoglycemia: insulin, cortisol, growth hormone, β-hydroxybutryate, plasma acylcarnitine profile, plasma amino acids and urine organic acids
      • Encephalopathy: ammonia, Liver “Function” Test (sp. ALT, AST, bilirubin)
      • Suspected galactosemia: urine reducing substances

How do you stabilize? (Note: Do not wait for labs to return to begin stabilization!)

Image Credit: Pixabay

  • ABCs (patients can present altered, apneic and/or in shock)
  • Recall the 2 main categories leading to emergencies: IEMs leading to intoxication and those resulting in energy defects (Ewing, 2009)
    1. Give Energy
      • Dextrose
        • Bolus as needed to treat hypoglycemia
        • Maintenance with D10 solutions
    2. Remove Toxins
      • Make NPO
      • Intravenous Fluids
        • D10 Half-normal saline run at 1-1.5x maintenance rate
      • Hemodialysis if indicated
        • Severe Hyperammonemia (Urea Cycle defects)

Next Steps?

Consultation with a metabolic specialist is essential!

  • Will help direct further diagnostic workup
  • Will help determine if further medical interventions (medications, vitamins, cofactors, etc)

 

Summary

  1. Inborn errors of metabolism present non-specifically
  2. Always consider IEM when presented with unwell neonate or infant
  3. For critically ill presentations, IEMs can be broken down into 2 main categories: Toxin Accumulation and/or Deficient Energy
    • Emergent Treatment (following ABCs) are directed at these two issues

Faculty Reviewer: Chanika Phornphutkul, MD

References

  • El-Hattab AW. “Inborn Errors of Metabolism.” Clinc Perinatol. 2015;1-27
  • Ewing, PH et al. “Evidence-Based Management Of Metabolic Emergencies In The Pediatric Emergency Department.” Pediatric Emergency Medicine Practice. 2009;6(10)1-16
  • Horeczko, Tim. “The Undifferentiated Sick Infant.” PEM Playbook.  http://pemplaybook.org/podcast/the-undifferentiated-sick-infant/. Accessed: 5/3/2017
  • Saudabray JM et al. ” Clinical approach to inherited metabolic disorders in neonates: an overview.” Semin Neonatol. 2002;7(1)3-15