Which assessment finding indicates that a therapeutic drug level has been achieved with magnesium sulfate for a client with PIH?

A decrease in respiratory rate from 24 to 16 is indicative of achieving a therapeutic drug level of magnesium sulfate in a client with pregnancy-induced hypertension (PIH). Magnesium sulfate acts as a CNS depressant and has a calming effect, which can lead to a decrease in respiratory effort as the client's overall muscle tone relaxes. Within the therapeutic range, the medication helps manage complications associated with PIH, such as seizures, by promoting relaxation and reducing excitability.

Monitoring respiratory Rate is crucial because magnesium sulfate can cause respiratory depression if levels become too high. A normal respiratory rate shows that the client is not experiencing adverse effects that would suggest toxicity, making this assessment finding a positive one in terms of therapeutic efficacy.

The other assessment findings do not necessarily correlate with achieving the desired effect of magnesium sulfate. Intact or exaggerated reflexes, such as 4+ reflexes, could indicate toxicity rather than a therapeutic range. Urinary output of 50 mL per hour may not be sufficient to support kidney function or indicate optimal drug clearance. A decreased body temperature is also not a primary indicator of magnesium sulfate’s effectiveness and can occur for various unrelated reasons.