What is the recommended dose of magnesium sulphate (magnesium sulfate) IV in ml/kg for children with severe acute asthma?

Dosage of Intravenous Magnesium Sulfate in Children with Severe Acute Asthma

The recommended dose of intravenous magnesium sulfate for children with severe acute asthma is 25-75 mg/kg (maximum 2-2.5 g) administered over 20 minutes as a single dose. 1

Indications for IV Magnesium Sulfate

IV magnesium sulfate should be administered when:

• The child has severe acute asthma not responding to initial treatment
• After conventional therapy with oxygen, nebulized beta-agonists, and systemic corticosteroids has been initiated
• As part of a comprehensive treatment protocol for severe asthma exacerbations

Dosing Protocol

1. Dose calculation: 25-75 mg/kg (maximum 2-2.5 g) 1
2. Administration rate: Infuse over 20 minutes as a single dose
3. Preparation: Use 50% magnesium sulfate solution diluted appropriately for IV administration
4. Timing: Administer after inadequate response to initial bronchodilator therapy

Monitoring During Administration

• Continuous clinical assessment of respiratory status
• Oxygen saturation monitoring
• Blood pressure monitoring (risk of hypotension)
• Heart rate monitoring
• Observation for signs of magnesium toxicity (levels 6-10 mmol/L) 1

Expected Clinical Outcomes

IV magnesium sulfate has been demonstrated to:

• Improve lung function parameters
• Reduce hospitalization rates
• Help prevent intubation in critically ill patients
• Provide earlier improvement in clinical signs and symptoms 1, 2

Studies have shown that magnesium sulfate administration results in faster resolution of retractions, wheeze, and dyspnea compared to other rescue medications 3.

Cautions and Contraindications

• Use with caution in patients with renal disease due to renal excretion of magnesium 1
• Contraindicated in patients with kidney failure or atrioventricular block 4
• Monitor for potential adverse effects, although these are rare when properly dosed

Integration with Standard Treatment Protocol

IV magnesium sulfate should be used as part of a comprehensive treatment approach that includes:

1. High-flow oxygen to maintain SaO₂ >92%
2. Short-acting beta-agonists via oxygen-driven nebulizer
3. Systemic corticosteroids (IV hydrocortisone or oral prednisolone)
4. Ipratropium bromide for severe exacerbations

Pharmacokinetic Considerations

Recent pharmacokinetic studies suggest that magnesium has a relatively short serum half-life (approximately 2.7 hours) in children 5. The target therapeutic range is estimated to be between 25-40 mg/L, which supports the recommended dosing range of 25-75 mg/kg 5.

Clinical Evidence Strength

Multiple studies have demonstrated the efficacy and safety of IV magnesium sulfate in children with severe acute asthma. A randomized controlled trial showed that magnesium sulfate had higher treatment success (97%) compared to terbutaline and aminophylline (both 70%) and with fewer adverse events 3. This supports its use as an effective and safe adjunct therapy for children with severe asthma exacerbations not responding to initial treatment.