Preparation of 4g 20% SOLUTION OF MAGNESIUM SULFATE (MgSO₄)
Wash hands thoroughly with soap and water or use an alcohol hand rub and air dry.
Using a 20-mL syringe, draw 12 mL of sterile water for injection. If 50% MgSO₄ is available, add 8 mL of MgSO₄ 50% solution (1 g/2 mL) to 12 mL of water for injection to make 20 mL of 20% solution (4 g per 20 mL). If the concentration is different, correctly mix 4 mg of MgSO₄ into 20 mL.
Administration of Loading Dose of MgSO₄
Establish an IV line using normal saline or Ringer’s lactate solution.
Using a 20-mL syringe, draw 4 g of MgSO₄ 50% (8 mL).
Add 12 mL of sterile water or saline to the same syringe to make a 20% solution.
Give this 4 g MgSO₄ 20% solution IV over 5–20 minutes.
Using two 20-mL syringes, draw 5 g of MgSO₄ 50% (10 mL) in each syringe.
Add 1 mL of 2% lignocaine to each of the two syringes.
Inject the first syringe by deep IM injection into one buttock (5 g MgSO₄).
Inject the second syringe by deep IM injection into the other buttock (5 g MgSO₄).
If convulsions recur after 15 minutes, give 2 g of MgSO₄ 20% by IV over 5 minutes.
To decontaminate: flush the needle and syringe with 0.5% chlorine solution three times; then place in a puncture-proof container.
Remove the gloves and discard them in a leakproof container or plastic bag.
Wash your hands thoroughly with soap and water
Monitoring for Signs of Toxicity
Count respiration rate for 1 minute every hour. The rate should be ≥ 16.
Patella reflexes should be present. Check every hour:
Place one hand under the woman’s knee and life her leg off the bed.
Tap the patellar tendon just below the kneecap with a reflex hammer.
Insert an indwelling urinary catheter and measure urinary output hourly. Output should be ≥30 mL/hour.
Administration of Maintenance Dose of MgSO₄
Before repeating administration of MgSO₄, check that: — Respiratory rate is at least 16 per minute. — Patellar reflexes are present. — Urinary output is at least 30 mL per hour over 4 hours.
Give 5 grams of MgSO₄ 50% solution together with 1 mL of 2% lignocaine in the same syringe, by deep IM injection into alternate buttocks (every 4 hours).
Withhold or delay the drug if:
The respiratory rate falls below 16 per minute
Patellar reflexes are absent.
Urinary output has fallen below 30 mL per hour over the preceding 4 hours.
In case of respiratory arrest,
Shout for help!
Assist ventilation with a mask and bag.
Give calcium gluconate (the antidote to MgSO₄) 1 g (10 mL of 10% solution) IV slowly.