A woman with preeclampsia is receiving magnesium sulfate. Which indicates to the nurse that the magnesium sulfate therapy is effective?

• A. Scotomas are present.
• B. Seizures do not occur.
• C. Ankle clonus is noted.
• D. The blood pressure decreases.

Answer: (B)

Magnesium sulfate in preeclampsia is given to prevent seizures. The key sign that this anticonvulsant therapy is working is that the patient does not develop seizures. If seizures occur, the therapy isn’t achieving its goal and adjustments are needed. Visual disturbances like scotomas or reflexive signs such as ankle clonus indicate ongoing CNS irritation from preeclampsia, suggesting the condition isn’t adequately controlled. A drop in blood pressure might occur, but it doesn’t prove that magnesium sulfate is effectively preventing seizures, since BP changes are not the primary measure of its efficacy. So, the best indicator of effectiveness is the absence of seizures.