Management of Fatty Acid Oxidation Defects During 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 during periods of increased metabolic demand or fasting. 2, 3 During viral illnesses, vomiting, or fasting, these patients are at high risk for:
- Hypoketotic hypoglycemia (the hallmark presentation) 1, 2
- Hepatic dysfunction and Reye-like syndrome 1
- Cardiomyopathy and rhabdomyolysis 1, 3
- Acute metabolic acidosis and encephalopathy 1
The fundamental problem is that these children cannot use fatty acids as an alternative fuel source when glucose stores are depleted, making continuous glucose provision essential. 2, 3
Evidence-Based Management Strategy
The American Association for the Study of Liver Diseases explicitly 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 for fatty acid oxidation defects. 1
Acute Illness Protocol
- Initiate IV glucose at ≥10 mg/kg/min immediately when illness begins 1
- Maintain serum glucose >100 mg/dL throughout the illness 1
- Monitor glucose levels frequently (every 2-4 hours initially) 4, 5
- Avoid any fasting periods, even brief ones 2, 3, 5
Why Other Options Are Incorrect
Option B (Fasting to promote ketone production) is contraindicated and dangerous. Patients with fatty acid oxidation defects develop hypoketotic hypoglycemia precisely because they cannot generate ketones from fatty acid metabolism. 1, 2 Fasting would precipitate metabolic crisis, not prevent it. 1, 5
Option C (High-fat diet) is contraindicated during acute illness. While some long-chain fatty acid oxidation defects require fat-modified diets during stable periods, fat restriction (not supplementation) is the dietary principle. 6 During acute illness, the priority is glucose provision, not fat. 1, 5
Option D (Protein restriction) is not relevant to fatty acid oxidation defects. Protein restriction is used in urea cycle defects and organic acidemias, not fatty acid oxidation disorders. 1, 5 These are distinct metabolic pathways.
Long-Term Prevention Strategy
Between illness episodes, management focuses on:
- Avoiding prolonged fasting (maximum fasting intervals vary by age and specific defect) 2, 3, 6
- Fat-restricted and fat-modified diet (strictest in long-chain defects) 6
- Medium-chain triglyceride supplementation (bypasses the defective enzymes) 6
- Carnitine supplementation (in approximately half of patients, though not universally required) 6
- Essential fatty acid supplementation (DHA for those on medium-chain fat-based diets) 2, 6
Critical Pitfalls to Avoid
Never allow elective fasting for procedures without IV glucose support. Prolonged fasting before anesthesia or diagnostic tests can precipitate metabolic crisis. 1 Any planned hospitalization or procedure requiring NPO status must include:
- Careful pre-procedure planning with metabolic team 1
- IV glucose infusion throughout the fasting period 1, 4
- Metabolic monitoring during the perioperative period 1, 4
Do not delay glucose administration during acute illness. Triggering events including febrile illnesses and vomiting can rapidly lead to severe complications. 1 Early aggressive treatment with IV glucose can reverse symptoms and prevent progression to fulminant liver failure. 1
Recognize that dietary management alone is insufficient during acute illness. While dietary interventions are effective for chronic management, acute metabolic decompensation requires intravenous glucose regardless of oral intake attempts. 1, 5
Prognosis with Appropriate Management
Prompt dietary and glucose intervention can reverse symptoms, including those associated with acute liver failure, and preclude the need for liver transplantation. 1 However, even with optimal management, some patients (particularly those with very long-chain acyl-CoA dehydrogenase deficiency and trifunctional protein complex disorders) may develop long-term complications including myopathy, peripheral neuropathy, and retinopathy. 6