A nurse is caring for a client who has preeclampsia and is receiving magnesium sulfate. The client reports that she is experiencing difficulty breathing. Which of the following actions should the nurse take first?

A. Administer calcium gluconate: Calcium gluconate is the antidote for magnesium sulfate toxicity, but it should be given after stopping the infusion and assessing the client’s respiratory status. Immediate discontinuation takes priority. B. Discontinue the infusion: Difficulty breathing indicates a potential magnesium sulfate toxicity or respiratory depression, which is a life-threatening emergency. The first action is to stop the infusion to prevent further accumulation. C. Assess the fetal heart rate: Monitoring the fetus is important, but maternal safety takes priority over fetal assessment in a potential toxic reaction. Stabilizing the mother comes first. D. Obtain the client's magnesium level: Lab assessment is useful for confirming toxicity, but it should not delay immediate intervention. Stopping the infusion takes precedence over obtaining levels.