The nurse performs an assessment of a pregnant woman who is receiving intravenous magnesium sulfate for preeclampsia and notes that the woman's deep tendon reflexes are absent. On the basis of this finding, the nurse should interpret?

• A. The magnesium sulfate is effective.
• B. The infusion rate needs to be increased.
• C. The woman is experiencing cerebral edema.
• D. The woman is experiencing magnesium excess.

Answer: (D)

Magnesium sulfate therapy can depress neuromuscular transmission, and the absence of deep tendon reflexes is a classic sign of magnesium toxicity. When reflexes disappear, magnesium levels are high enough to impair muscle function and threaten the patient's ability to breathe and maintain circulation. So, this finding is interpreted as magnesium excess, not that the medication is working or that seizures are being prevented.

Act quickly: stop or slow the magnesium infusion, monitor respirations and mental status, and notify the provider. Check the serum magnesium level and have calcium gluconate ready as the antidote if toxicity is suspected. Also continue close monitoring for signs of respiratory depression, hypotension, or bradycardia. This scenario is not about cerebral edema and does not indicate that the infusion rate should be increased.