Emergency situations

Warning signs that may indicate impending or actual metabolic decompensation in MCADD include:

• Lethargy or unusual drowsiness — may indicate energy deficit or hypoglycemia.
• Vomiting — particularly when persistent or accompanied by other signs.
• Hypoglycemia — low blood glucose; may manifest as shakiness, sweating, irritability, confusion.
• Altered consciousness — confusion, disorientation.
• Seizures — may result from severe hypoglycemia.
• Breathing difficulties — may indicate serious metabolic compromise.
• Liver dysfunction — hepatomegaly, elevated liver enzymes, jaundice.

MCADD metabolic decompensation can be rapidly fatal when not treated urgently. Historical (largely pre-newborn-screening) data quantify this risk:

• Iafolla 1994 (PMID 8120710): in a cohort of 120 affected children, 19% died before diagnosis was made.
• Lang 2009 (PMID 19821147): in adults presenting acutely, mortality was 50% (29% overall in that case series). Adult decompensation is typically precipitated by fasting or alcohol consumption.
• Orphanet: historically, approximately 25% of undiagnosed patients die during their first metabolic crisis.

Vomiting is dangerous in MCADD because:

1. It prevents caloric intake, leading to fasting.
2. It causes dehydration.
3. It may be a sign of metabolic decompensation itself.

When vomiting occurs:

• Attempt to provide glucose-containing fluids if possible.
• If vomiting persists and oral intake cannot be maintained, seek emergency medical attention.
• Do NOT assume vomiting will resolve on its own in a child with MCADD.

McGregor TL, et al. (2021) provides management principles for acute illness in MCADD, emphasizing the need for prompt medical evaluation when oral intake is compromised.

Diarrhea poses similar risks to vomiting:

• Reduces caloric absorption.
• Causes dehydration.
• May indicate intercurrent illness triggering decompensation.

Management: maintain hydration with glucose-containing oral rehydration solutions. If diarrhea is severe or persistent, seek medical attention.

Fever increases metabolic demand, which increases the body’s need for energy. In MCADD, this increased demand combined with reduced appetite (common during illness) creates a dangerous situation.

Management principles:

• Maintain caloric intake.
• Provide adequate hydration.
• Use antipyretics as directed by a physician.
• Monitor for signs of decompensation.
• If oral intake is compromised, seek medical attention.

When a person with MCADD cannot eat (due to illness, vomiting, or other causes), the risk of metabolic decompensation increases rapidly. The maximum safe period without intake depends on:

• Age (infants are most vulnerable).
• Clinical condition.
• Individual metabolic tolerance.
• Recent caloric status.

Infection is a major trigger for metabolic decompensation because:

• Increased metabolic demand (fever, immune response).
• Decreased appetite.
• Vomiting/diarrhea may accompany infection.
• Catabolic state promotes fatty acid oxidation.

All infections (viral, bacterial) can trigger decompensation. Management requires attention to both the infection itself and metabolic support. During intercurrent infections, an emergency dietary regimen must be available (Orphanet).

Dehydration worsens metabolic decompensation and can impair the body’s ability to maintain glucose homeostasis. Signs of dehydration include:

• Decreased urine output.
• Dry mucous membranes.
• Sunken eyes (in infants).
• Lethargy.
• Tachycardia.

Dehydration in the context of MCADD requires prompt medical attention.

These are medical emergencies that may indicate:

• Severe hypoglycemia.
• Metabolic encephalopathy.
• Impending or actual metabolic decompensation.

Hypoglycemia (low blood glucose) is a hallmark of metabolic decompensation in MCADD. It results from:

• Inability to produce energy from fatty acid oxidation during fasting.
• Inadequate ketogenesis (hypoketotic hypoglycemia).
• Depleted glycogen stores.

Hypoglycemia in MCADD is characteristically hypoketotic — blood glucose is low AND ketone bodies are inappropriately low, distinguishing it from hypoglycemia in other conditions where ketones may be elevated.

Management: in symptomatic patients, simple carbohydrates are administered orally (glucose tablets) or intravenously, until glycemia is maintained above 5 mmol/L (Orphanet).

Authoritative sources recommend that individuals with MCADD have an individualized emergency plan developed with their metabolic team. General principles from available sources include:

1. Prioritize the patient’s individualized emergency plan when available.
2. Maintain caloric intake — glucose-containing fluids/foods.
3. Seek medical attention when oral intake is compromised.
4. Do not fast during illness.
5. Emergency identification — medical alert bracelet/necklace.

McGregor TL, et al. (2021, Pediatrics) is an AAP Council on Genetics clinical report providing management principles for acute illness in MCADD, intended for pediatricians as primary care providers — emphasizing that although each patient has a primary metabolic physician, involvement of the primary care provider is crucial. Emergency medical treatment is necessary in cases of metabolic decompensation (Orphanet).

Glucose administration (verified): in symptomatic patients, simple carbohydrates are administered orally (glucose tablets) or intravenously, until glycemia is maintained above 5 mmol/L (Orphanet). GeneReviews similarly recommends simple carbohydrates by mouth (glucose tablets or sweetened, non-diet beverages) or IV fluids to reverse catabolism and prevent hypoglycemia.

Glucagon: the specific role of glucagon in MCADD emergency management remains insufficiently documented from primary sources in this research pass.