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Nursing QUESTION #9137
Question 1
A nurse is monitoring a woman receiving IV Magnesium Sulfate for eclampsia prophylaxis. Which finding requires IMMEDIATE cessation of the infusion and administration of the antidote?
  • Serum Mg²⁺ level of 4–7 mEq/L
  • Respiratory rate of 10/min with absent patellar reflexes✔
  • Urine output of 35 mL/hour
  • Mild sedation and flushing
Correct Answer Explanation

Magnesium Sulfate Toxicity monitoring is a critical nursing responsibility:

Serum Mg²⁺ LevelClinical Effect
\(1.5{-}2.5\,\text{mEq/L}\)Normal therapeutic range
\(4{-}7\,\text{mEq/L}\)Therapeutic anticonvulsant range
\(5{-}10\,\text{mEq/L}\)Loss of deep tendon reflexes (first sign of toxicity)
\(10{-}13\,\text{mEq/L}\)Respiratory paralysis ← DANGER
\(>15\,\text{mEq/L}\)Cardiac arrest

Stop infusion IMMEDIATELY if:

  • Respiratory rate \(<12/\text{min}\)
  • Absent patellar (deep tendon) reflexes — earliest clinical sign
  • Urine output \(<25{-}30\,\text{mL/hr}\) (Mg is renally excreted)
  • O₂ saturation falling

Antidote: Calcium Gluconate 1 g (10 mL of 10% solution) IV over 10 minutes — must be at bedside at all times.

Urine output of 35 mL/hr is acceptable (minimum 25–30 mL/hr). Flushing and sedation are normal side effects, not toxicity signs.