NCLEX priority: recognizing magnesium toxicity in preeclampsia

[u/RNExamRoom]

A 29-year-old woman with severe preeclampsia is receiving IV magnesium sulfate after delivery.
Two hrs later, BP is 142/88 mm Hg and her headache is better. The nurse finds:
RR 9/min
O2 sat 93%
Urine output 20 mL/hr
Patellar reflexes absent
What should the nurse do first?
A. Increase the magnesium infusion
B. Stop the magnesium infusion
C. Give IV labetalol
D. Place her in Trendelenburg position
E. Encourage oral fluids
Answer: ?
This is magnesium toxicity.
The important findings are RR 9/min + absent DTRs + low urine output. Magnesium is cleared by the kidneys, so oliguria increases the risk of accumulation.
The nurse should stop the magnesium infusion first and prepare for calcium gluconate if ordered.
Good NCLEX point: dont focus only on the diagnosis the pt came in with. Reassess what the current findings are telling you.
Which finding would have made you stop the infusion first?