What is the treatment for pediatric hypomagnesemia?

Treatment of Pediatric Hypomagnesemia

Magnesium is indicated for treatment of documented hypomagnesemia in pediatric patients, with the route and dosing determined by severity of deficiency and presence of symptoms. 1, 2

Initial Assessment and Diagnosis

Before initiating treatment, establish the diagnosis and severity:

• Hypomagnesemia is defined as serum magnesium <1.8 mg/dL (<0.74 mmol/L), with symptoms typically not appearing until levels fall below 1.2 mg/dL 3
• Check serum magnesium levels in all at-risk pediatric patients, including those with malabsorption, diarrhea, renal disorders, or on medications that increase magnesium losses 4
• Measure fractional excretion of magnesium to determine etiology: values <2% indicate gastrointestinal losses, while >2% suggests renal wasting 3
• Assess renal function before any magnesium supplementation to avoid life-threatening hypermagnesemia 3

Treatment Algorithm Based on Severity

Severe Symptomatic Hypomagnesemia (Serum Mg <1.2 mg/dL with symptoms)

Intravenous magnesium sulfate is required for symptomatic patients with severe deficiency:

• For life-threatening arrhythmias (torsades de pointes): Give 25-50 mg/kg IV (maximum 2 g) as bolus for pulseless torsades, or over 10-20 minutes for torsades with pulses 5
• For severe hypomagnesemia with tetany or seizures: Administer up to 250 mg/kg (approximately 2 mEq/kg) IM within 4 hours if necessary, or 5 g (approximately 40 mEq) added to one liter of IV fluid for slow infusion over 3 hours 2
• Rate of IV injection should generally not exceed 150 mg/minute to avoid hypotension and bradycardia 2
• Monitor continuously for magnesium toxicity: hypotension, bradycardia, respiratory depression, and have calcium chloride available for reversal 5

Moderate Hypomagnesemia (Serum Mg 1.2-1.8 mg/dL, asymptomatic)

Oral magnesium supplementation is appropriate for asymptomatic patients:

• For infants in hyperalimentation: Maintenance dose ranges from 2-10 mEq (0.25-1.25 g) daily 2
• For older children: Start with age-appropriate dosing based on recommended daily allowance (320 mg for females, 420 mg for males) and titrate upward as needed 5
• Administer magnesium at night when intestinal transit is slowest to improve absorption 5
• Use organic magnesium salts (aspartate, citrate, lactate) rather than magnesium oxide for better bioavailability, though magnesium oxide at 12-24 mmol daily is commonly used 5

Critical Precautions and Monitoring

Address underlying causes before supplementation:

• In patients with diarrhea or high gastrointestinal losses, correct sodium and water depletion first to address secondary hyperaldosteronism, which increases renal magnesium wasting 5
• Normalize magnesium levels before attempting to correct concurrent hypokalemia, as magnesium deficiency causes refractory hypokalemia through dysfunction of potassium transport systems 5
• Avoid magnesium supplementation if creatinine clearance <20 mL/min due to high risk of life-threatening hypermagnesemia 5

Monitor for complications:

• Magnesium produces vasodilation and may cause hypotension if administered rapidly 1
• Check serum magnesium, potassium, and calcium levels regularly during treatment 5
• Watch for signs of magnesium toxicity: hypotension, bradycardia, respiratory depression, loss of deep tendon reflexes 5
• In patients receiving continuous renal replacement therapy, use dialysis solutions containing magnesium to prevent ongoing losses 5

Special Considerations

For refractory status asthmaticus: Magnesium sulfate 25-50 mg/kg IV (maximum 2 g) over 15-30 minutes may be beneficial 5

Avoid prolonged continuous maternal administration beyond 5-7 days in pregnancy as this can cause fetal abnormalities 2

Most magnesium salts are poorly absorbed and may worsen diarrhea, so monitor gastrointestinal symptoms and adjust formulation if needed 5

The key pitfall is attempting to correct hypomagnesemia without first addressing volume depletion and hyperaldosteronism in patients with gastrointestinal losses, as ongoing renal wasting will exceed supplementation efforts. 5 Another common error is failing to recognize that hypokalemia will remain refractory until magnesium is normalized. 5