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For all procedures, ask yourself, 'does this need to be done 'now vs later'? And should this be done by 'me vs someone else?' Very often the answers will be 'now' and 'me' - so read on!

Eclamptic seizures


Management and prevention of eclamptic seizures in severe pre-eclampsia and eclampsia.


Eclamptic seizures and seizure prophylaxis in severe pre-eclampsia and eclampsia.


Relative - renal failure (reduce dose or magnesium).


Magnesium Sulphate IV
IV Pump


Magnesium Sulphate Protocol

Give a loading dose followed by a continuous infusion for 24 hours or until 24 hours after delivery – whichever is the later.

Loading dose:

MgSO4 4 -6 g IV diluted to 30mls over 15-20 minutes via a pump.

Maintenance dose:

MgSO4 1-2 g/hr IV infusion.

Clinical monitoring

Magnesium can cause respiratory depression and cardiac arrest - these are related to blood levels of magnesium.  Close monitoring with clinical assessment of the patient is essential. Re-evaluate the decision to continue the infusion, continuously.

Monitor the following:

  • continuous pulse oximetry
  • hourly urine output
  • hourly respiratory rate
  • deep tendon reflexes q4h
  • level of consciousness q4h

Only continue the infusion if, after each 4 hour period:

  • the biceps reflex is present
  • the respiratory rate is > 12/min.
  • the urine output is greater than 100 ml in the previous 4 hours

Side effects of MgSO4
  • motor paralysis
  • absent tendon reflexes
  • respiratory depression
  • cardiac arrhythmia
  • hypotension secondary to reductions in systemic vascular resistance
  • facial flushing
  • visual disturbances
  • flushing/necrosis at injection site
  • chest pain
  • nasal stuffiness

These can all occur, but will be minimized if MgSO4 is administered slowly and the patient is observed as above.


Calcium gluconate 10%
Dose: 1 g IV slowly over 10 minutes initially, if in arrest start at 1.5 – 3 g IV

Furosmide IV - as an adjunct to calcium gluconate - increases excretion of of magnesium

Potential pitfalls

Delay in starting Magnesium Sulphate in the woman with severe pre-eclampsia.
Inadequate monitoring of conscious level, respiratory rate, tendon reflexes and urine output.

"Plan B"

Discuss with a specialist unit.

BC Women’s Maternal-Fetal Medicine Team 604 875 2161

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Last modified: Thursday, 21 September 2023, 4:35 PM