Magnesium Sulfate Dosing for Pediatric Asthma Exacerbations
For pediatric patients with severe or life-threatening asthma exacerbations not responding to conventional therapy, intravenous magnesium sulfate should be administered at a dose of 25-50 mg/kg (maximum 2 grams) given over 15-30 minutes. 1
Indications for Use
Magnesium sulfate is indicated in the following scenarios:
- Life-threatening asthma exacerbations
- Severe asthma exacerbations that remain unresponsive after 1 hour of intensive conventional treatment
- Patients with very low FEV1 (<30% predicted, especially <20% predicted)
Dosing Protocol
Standard IV Bolus Dosing
- Dose: 25-50 mg/kg (maximum 2 grams)
- Administration: Given over 15-30 minutes
- Timing: After failure of first-line therapies (inhaled beta-agonists, anticholinergics, systemic corticosteroids)
Continuous Infusion (for refractory cases)
While less established in guidelines, some evidence supports continuous infusion for refractory cases:
- Loading dose: 25-75 mg/kg
- Maintenance: 40-50 mg/kg/hour for 4-5 hours 2, 3
- Target serum level: 4-6 mg/dL
Monitoring During Administration
- Vital signs, particularly blood pressure
- Oxygen saturation
- Clinical asthma score
- Respiratory status and effort
- Signs of magnesium toxicity:
- Hypotension
- Loss of deep tendon reflexes
- Respiratory depression
- Cardiac arrhythmias
Efficacy and Evidence
Intravenous magnesium sulfate has been shown to:
- Improve pulmonary function in children with moderate to severe asthma 4
- Increase percentage improvement in FEV1 (34% vs -1% at 50 minutes, 75% vs 5% at 110 minutes compared to placebo) 4
- Potentially reduce hospitalization rates 4
Important Considerations
- Magnesium sulfate has no apparent value in patients with exacerbations of lower severity 1
- Rapid infusion may cause hypotension and bradycardia 1
- Have calcium chloride available to reverse potential magnesium toxicity 1
- Early administration (within 60 minutes of arrival) has not been shown to reduce PICU admissions 5
Treatment Algorithm
First-line treatment:
- Oxygen supplementation
- Inhaled short-acting beta-agonists (albuterol/salbutamol)
- Systemic corticosteroids
- Consider ipratropium bromide
If poor response after 1 hour:
- Administer IV magnesium sulfate 25-50 mg/kg (max 2g) over 15-30 minutes
If still inadequate response:
- Consider continuous magnesium infusion in refractory cases
- Evaluate for ICU transfer if deteriorating
Cautions
- Monitor for hypotension, especially with rapid administration
- Use with caution in patients with renal impairment
- Be alert for signs of magnesium toxicity, particularly at higher doses or with prolonged administration
- The most common adverse effects with prolonged infusions include hypotension (16.6%), nausea/vomiting (7.8%), and mild muscle weakness (4.9%) 2
Magnesium sulfate should be considered an important adjunctive therapy for pediatric patients with severe asthma exacerbations not responding to conventional treatments, with evidence supporting its efficacy in improving pulmonary function and potentially reducing hospitalization rates.