A patient with severe pre-eclampsia at 32 weeks is stabilised with MgSO₄. Four hours later she becomes areflexic with a respiratory rate of 10/min. The next immediate step is:
- A Reduce MgSO₄ infusion to 1 g/hour
- B Stop MgSO₄ and give calcium gluconate 1 g IV slowly ✓
- C Check serum Mg²⁺ level before any intervention
- D Intubate and ventilate immediately
Correct answer: B. Stop MgSO₄ and give calcium gluconate 1 g IV slowly
Explanation
Loss of deep tendon reflexes is the earliest sign of MgSO₄ toxicity (serum Mg 7–10 mEq/L); respiratory depression follows (>10 mEq/L). The antidote is calcium gluconate 1 g (10 mL of 10% solution) given IV over 3 minutes, which reverses magnesium toxicity within minutes. MgSO₄ must be stopped simultaneously. Waiting for a serum level wastes critical time in a patient who is already symptomatic.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.