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

Choice A reason: A change in deep tendon reflexes from 4+ (hyperreflexic) to 2+ (normal) indicates magnesium sulfate’s therapeutic effect in preeclampsia, as it reduces neuronal excitability, preventing seizures. Magnesium stabilizes nerve membranes, lowering seizure risk by modulating calcium channels, aligning with its anticonvulsant role in preeclampsia management. Choice B reason: A fetal heart rate increase from 150/min to 166/min is not a direct indicator of magnesium sulfate’s effectiveness. Magnesium primarily prevents maternal seizures, not fetal heart rate changes. This increase may reflect fetal stress or normal variation, unrelated to magnesium’s neurological stabilization in preeclampsia treatment. Choice C reason: Minimal fetal heart rate variability suggests fetal compromise, not magnesium sulfate’s desired effect. Magnesium aims to prevent maternal seizures without significantly altering fetal heart patterns. Reduced variability may indicate hypoxia, requiring separate intervention, as it does not reflect the drug’s therapeutic goal of maternal neurological stabilization. Choice D reason: Urinary output of 20 mL/hr indicates potential magnesium toxicity or renal impairment, not therapeutic effectiveness. Magnesium sulfate requires adequate renal excretion to avoid toxicity, and output below 30 mL/hr suggests accumulation, risking respiratory depression or cardiac effects, contrary to the drug’s intended anticonvulsant action in preeclampsia.