Hypoglycaemia in Children
Hypoglycaemia is a clinical state resulting from an abnormally low blood glucose concentration. It’s a medical emergency in children, as the brain relies on a constant supply of glucose for normal function. A prompt diagnosis and management are vital to prevent long-term neurological damage.
Definition
The threshold for hypoglycaemia varies with age and clinical context, but a plasma glucose level of <2.6 mmol/L is a commonly used threshold in neonates and young infants. In older children, a glucose level of <3.0 mmol/L with symptoms is generally considered significant.
Causes
Hypoglycaemia can be caused by a variety of factors, and the timing of the hypoglycaemia (fasting vs. post-prandial) is a key clue to the underlying aetiology.
Fasting Hypoglycaemia: Occurs after a period of fasting.
Hyperinsulinism: The most common cause of persistent hypoglycaemia in infants. It can be congenital or due to conditions like Beckwith-Wiedemann syndrome.
Endocrine Deficiencies: Conditions like Congenital Adrenal Hyperplasia (CAH), hypopituitarism, or growth hormone deficiency.
Ketotic Hypoglycaemia: A common cause in young children (18 months to 5 years). It’s a diagnosis of exclusion and is often triggered by an intercurrent illness.
Post-prandial (Reactive) Hypoglycaemia: Occurs after a meal.
Iatrogenic: A common cause in children with diabetes on insulin.
Other Causes:
Metabolic Disorders: Inborn errors of metabolism, such as glycogen storage diseases.
Infection: Sepsis is a key cause of hypoglycaemia due to increased glucose consumption.
Ingestion: Accidental ingestion of drugs like sulphonylureas.
Clinical Presentation
The clinical presentation can be subtle and non-specific, particularly in young infants. Symptoms are often divided into two groups:
Adrenergic Symptoms: These are a result of the body’s counter-regulatory response and include a rapid heart rate, sweating, tremor, and anxiety.
Neuroglycopenic Symptoms: These are caused by a lack of glucose to the brain and include lethargy, irritability, confusion, and, in severe cases, seizures and coma.
Investigations
A blood sample should be taken during a hypoglycaemic episode (critical sample) and sent for a wide range of investigations to determine the cause.
Initial Tests:
Glucose: To confirm hypoglycaemia.
Ketones: In ketotic hypoglycaemia, ketones will be present in the urine or blood. The absence of ketones in a fasting state suggests hyperinsulinism.
U&Es: To check for electrolyte abnormalities.
Critical Sample:
Insulin, C-peptide, and Cortisol: These are crucial for distinguishing between different types of hypoglycaemia.
Lactate, Ammonia, and Amino Acids: To screen for an inborn error of metabolism.
Management
Management is based on the severity of the hypoglycaemia.
Acute Management:
Conscious Child: Give oral glucose (e.g., a sugary drink or glucose gel).
Unconscious Child: Give intravenous glucose (10% dextrose, 2 mL/kg) or intramuscular glucagon.
Long-Term Management:
Hyperinsulinism: May require medical therapy or, in some cases, a partial pancreatectomy.
Ketotic Hypoglycaemia: Requires dietary advice to ensure frequent meals and snacks.
Endocrine Deficiencies: Requires hormone replacement therapy.
Inborn Errors of Metabolism: Requires a specialist metabolic team for diagnosis and management.