patient with ongoing magnesium sulfate the nurse should be alert to ?

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Core Concept: Magnesium sulfate is a CNS depressant and smooth muscle relaxant commonly used in obstetrics for seizure prophylaxis in preeclampsia/eclampsia. Because magnesium is excreted entirely by the kidneys, toxicity can occur rapidly. The earliest and most critical signs of magnesium toxicity involve the loss of deep tendon reflexes followed by severe respiratory depression and cardiac arrest.

Clinical Presentation:

• Magnesium toxicity presents with diminished or absent deep tendon reflexes (hyporeflexia), muscle weakness, flushing, hypotension, and lethargy.
• As levels rise, it causes severe respiratory depression (bradypnea) and eventually cardiac arrest.
• Complications include maternal respiratory failure and fetal distress.

Diagnosis:

• First-line diagnostic tool: Nursing assessments including monitoring respiratory rate (must be > 12-16 breaths/min), urine output (must be > 30 mL/hr), and deep tendon reflexes (DTRs).
• Gold standard diagnostic test: Serum magnesium level (therapeutic range for preeclampsia is typically 4-7 mEq/L; toxicity signs appear > 8-10 mEq/L).

Management:

• Acute management: Immediately stopping the magnesium sulfate infusion and providing respiratory support if needed.
• Gold standard long-term/definitive management (antidote): The slow intravenous administration of Calcium Gluconate or Calcium Chloride to antagonize the cardiac and respiratory effects of severe magnesium toxicity.