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

A. Respiratory rate 10/min. This is the priority finding because it suggests respiratory depression, a serious side effect of magnesium sulfate therapy. Magnesium acts as a CNS depressant, and a respiratory rate below 12/min is a potential sign of magnesium toxicity, which can lead to respiratory arrest if not promptly addressed. B. 2+ deep-tendon reflexes. This indicates normal neuromuscular function and is actually a reassuring finding in a client receiving magnesium sulfate. Reflexes are typically monitored to detect early signs of toxicity, and a 2+ rating means the dose is likely therapeutic. C. 3+ pedal edema. While significant, pedal edema is a common feature of preeclampsia and not directly related to magnesium sulfate toxicity. It should be monitored but does not require immediate action compared to respiratory compromise. D. Urinary output 35 mL/hr. This is slightly above the minimum acceptable output of 30 mL/hr, indicating the kidneys are excreting adequately. While magnesium is excreted renally and output must be monitored, this value does not indicate an acute risk.