Administration

Loading dose:

• Give 4 g IV over 5 minutes
• If already on MgS04 then give 2 g over 10 minutes
• If no IV access, Give 5 g of 50% magnesium sulphate solution with 1 mL of 2% lignocaine in the same syringe by deep IM injection

Maintenance dose:

• Infusion at 1 g/hour for 24 hours
• Give 5 g of 50% magnesium sulphate solution with 1 mL of 2% lignocaine in the same syringe by deep IM injection into alternate buttocks every four hours

Monitoring

Pay particular attention to:

• ECG monitoring (can develop heart block in toxicity)
• BP monitoring
• Oxygen saturation
• Patellar reflexes regularly to check for signs of toxicity

Precautions

Look out for:

• Magnesium toxicity
• Normal Magnesium level is 0.7-1.0 mmol
• Symptoms of toxicity:
  • Severe flushing
  • Headache
  • Nausea and vomiting, muscle weakness
  • Loss of tendon reflexes
  • Respiratory paralysis
  • Cardiac arrest
• Increased risk of magnesium toxicity:
  • In renal failure
  • In myasthenia gravis
  • Concurrent treatment with nifedipine
  • Hepatic coma

Treatment of toxicity

When treating toxicity:

• Stop MgS04 infusion
• Support ABC as needed
• Give 1 g of calcium gluconate over 10 minutes
• Restart MgS04 at half previous rate once patient stabilized

nb. image provided in ppt deck