A woman with severe pre-eclampsia at 34 weeks is on IV magnesium sulfate. She develops a respiratory rate of 10/min, loss of deep tendon reflexes, and oxygen saturation of 88%. The correct immediate management is:
- A Reduce magnesium infusion rate to 0.5 g/hr and administer IV furosemide
- B Stop magnesium infusion; give 10 mL of 10% calcium gluconate IV and provide respiratory support ✓
- C Administer IV naloxone and prepare for emergency intubation
- D Stop magnesium and give IV sodium bicarbonate to correct acidosis
Correct answer: B. Stop magnesium infusion; give 10 mL of 10% calcium gluconate IV and provide respiratory support
Explanation
Magnesium toxicity progresses: first, loss of patellar reflexes (>8 mEq/L), then respiratory depression (>12 mEq/L), then cardiac arrest (>15 mEq/L). The antidote is calcium gluconate (10 mL of 10% solution given IV over 10 minutes), which antagonizes the membrane effects of magnesium. The infusion must be stopped immediately. Oxygen supplementation and assisted ventilation are also required. Naloxone is the antidote for opioid toxicity, not magnesium toxicity.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.