A woman with severe pre-eclampsia at 28 weeks receives antenatal corticosteroids and magnesium sulfate. Her magnesium level returns as 9.5 mEq/L. Which clinical finding is MOST LIKELY to be present at this level?
- A Loss of deep tendon reflexes ✓
- B Respiratory depression
- C Cardiac arrest
- D Drowsiness and slurred speech
Correct answer: A. Loss of deep tendon reflexes
Explanation
Magnesium toxicity progresses in a predictable sequence: loss of patellar (deep tendon) reflexes occurs at 7–10 mEq/L, respiratory depression at 10–13 mEq/L, and cardiac arrest at >15 mEq/L. At 9.5 mEq/L, loss of deep tendon reflexes is the expected finding and serves as the clinical warning sign to stop or reduce the infusion before respiratory compromise occurs.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.