A pre-eclamptic patient at term is on magnesium sulfate infusion at 2 g/h. She develops reduced deep tendon reflexes and oliguria (15 mL/h). Serum magnesium level is 9.2 mg/dL. The most appropriate immediate action is:
- A Discontinue magnesium infusion and administer calcium gluconate 1 g IV ✓
- B Reduce magnesium infusion to 1 g/h and monitor closely
- C Administer furosemide 40 mg IV to improve urine output
- D Add oral nifedipine to reduce the need for magnesium
Correct answer: A. Discontinue magnesium infusion and administer calcium gluconate 1 g IV
Explanation
A serum magnesium of 9.2 mg/dL (therapeutic range 4–7 mg/dL; loss of DTRs occurs at 7–10 mg/dL; respiratory arrest at 10–13 mg/dL) with lost DTRs and oliguria signals magnesium toxicity. The infusion must be stopped immediately and calcium gluconate 1 g IV given as a magnesium antagonist — it competitively reverses neuromuscular blockade within minutes. Reducing the dose is insufficient given the level, and furosemide does not address the primary toxicity.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.