A nurse is assessing a client who is receiving magnesium sulfate for preeclampsia. Which of the following findings is the nurse's priority?

A. 2+ deep-tendon reflexes: This is a normal reflex response and indicates that magnesium levels are not excessively high. Diminished or absent reflexes would be a more concerning sign of toxicity. B. Respiratory rate 10/min: A respiratory rate below 12/min suggests respiratory depression, which is a serious adverse effect of magnesium sulfate toxicity. This is the priority finding requiring immediate intervention. C. Urinary output 35 mL/hr: This is slightly above the minimum expected output of 30 mL/hr. While renal function must be monitored to prevent magnesium accumulation, this rate is adequate for now. D. Pedal edema: Edema is common in preeclampsia and is not an urgent concern compared to signs of magnesium toxicity such as respiratory depression.