Final answer:
The most critical assessment for a client receiving IV magnesium sulfate is the monitoring of hourly deep tendon reflexes (DTRs) due to the potential for magnesium toxicity affecting neuromuscular function.
Step-by-step explanation:
The critical assessment parameter for a client receiving intravenous (IV) magnesium sulfate is hourly deep tendon reflexes (DTRs). This is because magnesium has a direct effect on neuromuscular function, and high levels of magnesium can lead to decreased reflexes. Monitoring DTRs will help assess for signs of magnesium toxicity. Continuous monitoring of urine output, such as a 24-hour urine collection, is important to measure kidney function and the excretion of magnesium, but it is not as critical as observing DTRs in this context. Monitoring for symptoms of depression or monitoring serum calcium levels may be relevant to the overall care of the patient but are not as directly related to the administration of magnesium sulfate as DTRs.