Management of Fatty Acid Oxidation Defects During Acute Illness
Continuous glucose infusion (Option A) is the most effective measure to prevent metabolic decompensation in children with fatty acid oxidation defects during illness episodes. 1
Pathophysiology and Rationale
Children with fatty acid oxidation defects cannot properly metabolize fatty acids for energy, placing them at high risk for hypoketotic hypoglycemia, hepatic dysfunction, cardiomyopathy, rhabdomyolysis, and Reye-like syndrome during viral illnesses, vomiting, or fasting. 2, 1, 3, 4 These patients are unable to convert fatty acids into energy substrates, resulting in decreased ATP and glucose availability for high-energy-requiring organs. 4
Evidence-Based Acute Management Protocol
The American Association for the Study of Liver Diseases recommends intravenous glucose infusion of at least 10 mg/kg/min to maintain serum glucose above 100 mg/dL during a crisis as first-line therapy. 2, 1
Specific Implementation Steps:
- Initiate IV glucose at ≥10 mg/kg/min immediately when illness begins to prevent metabolic crisis 1
- Maintain serum glucose >100 mg/dL throughout the illness to ensure adequate energy supply and prevent lipolysis 2, 1
- Continue glucose infusion until the child can tolerate adequate oral carbohydrate intake 5, 6
Why Other Options Are Incorrect
Option B (Fasting to promote ketone production) is absolutely contraindicated. These patients have hypoketotic hypoglycemia—they cannot produce adequate ketones from fatty acid oxidation. 3, 4 Fasting would precipitate severe metabolic decompensation and potentially death. 1, 5
Option C (High-fat diet) is contraindicated during acute illness. Long-chain fatty acid oxidation defects specifically require fat restriction (10% of total energy from long-chain triglycerides), not increased fat intake. 6 During illness, these patients need glucose, not fat, as their primary fuel source. 1, 6
Option D (Protein restriction) has no role in fatty acid oxidation defects. Unlike urea cycle disorders or organic acidemias, protein restriction is not indicated in FAODs. 5, 6
Critical Pitfalls to Avoid
- Never allow elective fasting for procedures without IV glucose support, as prolonged fasting can precipitate metabolic crisis 1
- Do not delay glucose administration during acute illness—early aggressive treatment with IV glucose can reverse symptoms and prevent progression to fulminant liver failure 2, 1
- Do not rely on dietary management alone during acute illness—intravenous glucose is required regardless of oral intake attempts 1, 6
- Avoid the misconception that these patients need ketones—they have hypoketotic hypoglycemia and cannot generate adequate ketones 3, 4
Long-Term Preventive Measures
Between illness episodes, management includes avoiding fasting, maintaining frequent carbohydrate-rich meals, and in long-chain defects, restricting long-chain triglycerides while supplementing medium-chain triglycerides. 5, 6 However, during acute illness, continuous IV glucose supersedes all other interventions. 1
Prognosis with Appropriate Management
Prompt glucose intervention can reverse symptoms, including those associated with acute liver failure, and preclude the need for liver transplantation. 2, 1 The maximum rate of dextrose administration without producing glycosuria is 0.5 g/kg/hour, with about 95% retained when infused at 0.8 g/kg/hour. 7