A nurse is collecting data from a client who is receiving magnesium sulfate via continuous IV infusion to treat preeclampsia. Which of the following findings indicates that the medication is having a therapeutic effect?

A. Positive clonus: Clonus indicates neuromuscular irritability and is a sign of worsening preeclampsia rather than therapeutic control. The presence of clonus suggests inadequate suppression of central nervous system excitability. B. Respiratory rate 10/min: A respiratory rate of 10 per minute indicates respiratory depression, which is a sign of magnesium toxicity. This finding reflects an adverse effect rather than a therapeutic response. C. Deep tendon reflexes 2+: Normal deep tendon reflexes indicate that magnesium levels are within the therapeutic range. This finding reflects effective seizure prophylaxis without evidence of magnesium toxicity. D. Urinary output 20 mL/hr: Low urine output suggests impaired renal clearance of magnesium, increasing the risk for toxicity. Adequate urine output is needed to safely eliminate magnesium, so this finding is concerning rather than therapeutic.