Define Hypokalaemia in Children. Describe its causes, clinical features, management and prevention.

Definition

• Hypokalaemia is a serum potassium < 3.5 mmol/L.
• Potassium is the major intracellular cation, essential for neuromuscular and cardiac function, so its depletion produces characteristic and potentially dangerous effects.

Causes

• GI loss (commonest in children) — diarrhoea, vomiting, laxatives, ileostomy.
• Renal loss — diuretics, renal tubular acidosis, Bartter/Gitelman syndrome, hyperaldosteronism.
• Transcellular shift — alkalosis, insulin, β-agonists (salbutamol), refeeding.
• Inadequate intake (severe malnutrition — total-body K depleted even if serum K is normal).

Clinical Features

• Neuromuscular — muscle weakness, hypotonia, cramps; in severe cases flaccid paralysis.
• Gastrointestinal — paralytic ileus with abdominal distension and constipation.
• Cardiac — arrhythmias; ECG shows flat/inverted T waves, prominent U waves, ST depression.
• Renal — polyuria (impaired concentrating ability).

Management

• Treat the cause and correct associated dehydration/alkalosis.
• Mild: oral potassium (KCl) and potassium-rich foods (banana, coconut water, citrus).
• Severe / symptomatic / arrhythmia: cautious IV KCl (diluted, never a rapid push), with ECG & serum monitoring.
• Correct associated magnesium deficiency (hypokalaemia is refractory until magnesium is replaced).

ECG Changes (in Order of Severity)

• Flattening/inversion of T waves → appearance of U waves → ST-segment depression → arrhythmias.
• These changes warrant urgent, monitored potassium correction.

Prevention

• Add potassium to maintenance/deficit fluids once urine output is established.
• Encourage potassium-rich foods in at-risk children; correct magnesium alongside.

Key Principle

• Hypokalaemia commonly accompanies diarrhoea, vomiting and malnutrition.
• Always add potassium to rehydration fluids once the child is passing urine, give potassium-rich foods on recovery, and correct any coexisting magnesium deficiency, which otherwise makes the low potassium resistant to treatment.