All of the following can be signs of magnesium toxicity EXCEPT:

• A. Decreased urine output
• B. Respiratory depression
• C. Increased alertness
• D. Cardiac arrhythmias

Answer: (C)

Magnesium toxicity can present through various clinical signs, and increased alertness is not one of them. When magnesium levels rise excessively in the body, it leads to a range of symptoms that indicate the body is unable to handle the excess magnesium. Decreased urine output occurs because the kidneys are not effectively excreting magnesium, leading to its accumulation. Respiratory depression can result from the effect of high magnesium levels on the central nervous system, leading to decreased effort in breathing. Cardiac arrhythmias may arise from the disruption of electrical conduction in the heart due to excessive magnesium, which can affect heart rhythm.

In contrast, increased alertness is unlikely to manifest; instead, patients might experience decreased alertness, lethargy, or coma as magnesium levels rise. Thus, the presence of increased alertness would not be a sign of magnesium toxicity, making it the correct answer in this scenario.