A nurse is caring for a client who is at 35 weeks of gestation and is receiving magnesium sulfate for treatment of preeclampsia. Which of the following findings indicates that the medication is having the desired effect?

Choice A rationale Urinary output of 20 mL/hr is indicative of oliguria, which is a significant adverse effect of magnesium sulfate therapy. Magnesium is renally excreted, and decreased urinary output can lead to magnesium toxicity. The desired urinary output for a client receiving magnesium sulfate should be at least 25 to 30 mL/hr to ensure adequate drug excretion. Choice B rationale Fetal heart rate pattern with minimal variability is a concerning finding and can indicate central nervous system depression in the fetus, potentially due to excessive magnesium levels. Normal fetal heart rate variability reflects a healthy autonomic nervous system. Magnesium sulfate's therapeutic effect is on the mother, not directly on fetal heart rate variability. Choice C rationale A change in fetal heart rate from 150/min to 166/min, while still within the normal range (110-160 bpm), does not directly indicate the desired therapeutic effect of magnesium sulfate for preeclampsia. This fluctuation could be due to various factors and is not a primary indicator of successful seizure prophylaxis or blood pressure control. Choice D rationale Magnesium sulfate is a central nervous system depressant that works by blocking neuromuscular transmission, thereby reducing hyperreflexia associated with preeclampsia. A decrease in deep tendon reflexes from 4+ (hyperactive) to 2+ (normal) indicates that the medication is achieving its desired therapeutic effect of central nervous system depression and reducing seizure risk.