Which parameters should be monitored to detect magnesium toxicity?

• A. Blood pressure, heart rate, and skin color
• B. Deep tendon reflexes, respiratory rate, and urine output
• C. Hematocrit, platelets, and bilirubin
• D. Temperature, oxygen saturation, and mental status

Answer: (B)

The essential idea is that magnesium toxicity shows up as neuromuscular and respiratory slowing, so you watch for changes in deep tendon reflexes, breathing, and kidney function. Deep tendon reflexes tend to become depressed as magnesium rises, so loss or slowing of reflexes is an early sign. The respiratory rate drops when magnesium causes muscle weakness and CNS depression, making it a critical safety measure. Urine output matters because magnesium is excreted by the kidneys; reduced urine output can indicate impaired clearance and the potential for accumulation. Together, these three parameters give real-time, clinically relevant clues about magnesium toxicity and guide whether to hold the infusion or treat with calcium gluconate if needed.

Other parameters like blood pressure, heart rate, and skin color are nonspecific and can change for many reasons. Laboratory values such as hematocrit, platelets, and bilirubin reflect different organ systems and aren’t direct indicators of magnesium level. Temperature, oxygen saturation, and mental status may be influenced by numerous conditions and don’t pinpoint magnesium toxicity as reliably.