Magnesium Sulfate

Magnesium Sulfate in Pediatric Emergency Medicine

Magnesium sulfate is a versatile electrolyte with multiple applications in pediatric emergency medicine. It acts as a physiological calcium channel blocker, leading to smooth muscle relaxation, bronchodilation, and various other effects.

Key Points:

Essential in managing severe asthma exacerbations and certain arrhythmias
Neuroprotective in preterm labor management
Available in different concentrations; careful dose calculation is crucial
Can cause serious side effects if administered incorrectly
Requires close monitoring during and after administration

Indications for Magnesium Sulfate Use in Pediatrics

Severe acute asthma exacerbations unresponsive to conventional therapy
Torsades de pointes
Hypomagnesemia
Eclampsia in adolescent pregnancies
Neuroprotection in preterm labor (for fetuses <32 weeks gestation)
Rapid sequence intubation in status asthmaticus
Resistant ventricular fibrillation
Digoxin-induced arrhythmias

Dosage and Administration

Severe Acute Asthma:

25-75 mg/kg/dose (max 2 grams) IV over 20 minutes

Torsades de Pointes:

25-50 mg/kg (max 2 grams) IV push over 1-2 minutes

Hypomagnesemia:

25-50 mg/kg/dose (max 2 grams) IV over 4 hours

Eclampsia:

Loading dose: 4-6 grams IV over 15-20 minutes
Maintenance: 1-2 grams/hour continuous infusion

Neuroprotection in Preterm Labor:

Loading dose: 4 grams IV over 20-30 minutes
Maintenance: 1 gram/hour for 24 hours or until delivery

Note: Concentrations commonly used are 10% (100 mg/mL) and 50% (500 mg/mL). Always double-check calculations and dilute as necessary.

Precautions and Side Effects

Precautions:

Use with caution in patients with renal impairment
Monitor for signs of magnesium toxicity
Be aware of potential interactions with neuromuscular blocking agents
Avoid in patients with heart block
Use cautiously in patients with myasthenia gravis

Side Effects:

Flushing, sweating
Hypotension
Respiratory depression
Muscle weakness
Nausea and vomiting
Loss of deep tendon reflexes (early sign of toxicity)
Cardiac conduction abnormalities
In severe toxicity: paralysis, apnea, cardiac arrest

Monitoring

Continuous cardiac monitoring
Frequent blood pressure measurements
Respiratory rate and depth
Oxygen saturation
Deep tendon reflexes
Urine output
Serum magnesium levels (therapeutic range: 4-7 mEq/L)
Calcium levels (magnesium can cause hypocalcemia)
ECG for prolonged PR interval, widened QRS complex

Antidote:

In case of magnesium toxicity, calcium gluconate (100 mg/kg, max 1 gram) can be given IV slowly as an antidote.