What is the recommended dose of magnesium sulfate for a 24 kg child with acute asthma exacerbation?

Magnesium Sulfate Dosing for a 24 kg Child with Acute Asthma Exacerbation

For a 24 kg child with severe acute asthma exacerbation, the recommended dose of intravenous magnesium sulfate is 25-75 mg/kg (600-1800 mg) administered over 20 minutes. 1

Indications for Magnesium Sulfate in Pediatric Asthma

• Magnesium sulfate should be considered for severe asthma exacerbations that remain severe after 1 hour of intensive conventional treatment with inhaled β2-agonists, anticholinergics, and systemic corticosteroids 1, 2
• Particularly indicated for life-threatening exacerbations and patients with poor response to initial therapy 1
• IV magnesium sulfate is recommended by multiple guidelines for severe exacerbations of asthma in children 3, 2

Dosing Specifics

• The National Asthma Education and Prevention Program Expert Panel recommends 25-75 mg/kg IV (maximum 2 g) for children 1
• For a 24 kg child, this translates to 600-1800 mg of magnesium sulfate 1
• The medication should be administered over 20 minutes to prevent adverse effects 1, 4
• Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration 4

Administration Protocol

1. Dilute magnesium sulfate in 5% Dextrose Injection or 0.9% Sodium Chloride Injection to a concentration of 20% or less 4
2. Administer the calculated dose (600-1800 mg) intravenously over 20 minutes 1
3. Monitor vital signs, particularly blood pressure, during administration 1
4. Have calcium chloride immediately available to reverse potential magnesium toxicity if needed 1, 5

Mechanism of Action and Efficacy

• Magnesium causes bronchial smooth muscle relaxation independent of serum magnesium level 2, 1
• It provides a complementary bronchodilator effect when combined with nebulized β-adrenergic agents and corticosteroids 2
• IV magnesium sulfate moderately improves pulmonary function and can reduce hospital admissions in patients with severe asthma exacerbations 2

Safety Considerations

• IV magnesium sulfate generally has a favorable safety profile with only minor side effects such as flushing and light-headedness 1
• Rapid infusion may cause hypotension and bradycardia, which is why administration over 20 minutes is recommended 1
• Continuous maternal administration of magnesium sulfate in pregnancy beyond 5-7 days can cause fetal abnormalities (not applicable in this pediatric case) 4

Important Clinical Considerations

• Magnesium sulfate should be used as an adjunct to standard therapy (inhaled β2-agonists, anticholinergics, and systemic corticosteroids), not as a replacement 2, 1
• Some studies have found that higher doses of magnesium sulfate (>27 mg/kg) may be associated with an increased need for escalation in therapy, suggesting that moderate dosing may be preferable 6
• A prospective study showed that a single bolus infusion of IV magnesium sulfate at 50 mg/kg was safe in children receiving it for acute asthma 7

Treatment Algorithm for Severe Asthma Exacerbations

1. Initial treatment with inhaled short-acting β2-agonists, anticholinergics, and systemic corticosteroids 2, 1
2. If exacerbation remains severe after 1 hour of intensive treatment, consider IV magnesium sulfate 1
3. For a 24 kg child, administer 25-75 mg/kg (600-1800 mg) over 20 minutes 1
4. Continue monitoring respiratory status and response to treatment 1