Which finding would indicate magnesium sulfate toxicity?

Which finding would indicate magnesium sulfate toxicity?

• A. Urine output 90 ml/4 hours.
• B. Deep tendon reflexes 2+.
• C. Blood pressure 140/90.
• D. Respiratory rate 18/minute.

Answer: (A)

Magnesium sulfate toxicity shows up when levels are high enough to dampen neuromuscular and autonomic functions. A key sign to watch for is reduced urine output, because magnesium is cleared by the kidneys; when kidneys aren’t producing enough urine, magnesium can accumulate and worsen toxicity. A urine output of 90 mL over 4 hours is below the expected amount for an adult patient and suggests oliguria, which can reflect magnesium build-up and the need to reassess the infusion and renal function. This is the finding that signals potential toxicity in this scenario. Normal deep tendon reflexes (2+), normal respiratory rate (not depressed), and a blood pressure that is not markedly low do not point to magnesium toxicity in this context. While magnesium toxicity can eventually cause decreased reflexes, respiratory depression, or hypotension, these signs are not present here, making reduced urine output the most concerning clue in this set. If toxicity is suspected, clinicians would typically pause the infusion, monitor respiratory status, check reflexes, and measure serum magnesium levels.

Magnesium sulfate toxicity shows up when levels are high enough to dampen neuromuscular and autonomic functions. A key sign to watch for is reduced urine output, because magnesium is cleared by the kidneys; when kidneys aren’t producing enough urine, magnesium can accumulate and worsen toxicity. A urine output of 90 mL over 4 hours is below the expected amount for an adult patient and suggests oliguria, which can reflect magnesium build-up and the need to reassess the infusion and renal function. This is the finding that signals potential toxicity in this scenario.

Normal deep tendon reflexes (2+), normal respiratory rate (not depressed), and a blood pressure that is not markedly low do not point to magnesium toxicity in this context. While magnesium toxicity can eventually cause decreased reflexes, respiratory depression, or hypotension, these signs are not present here, making reduced urine output the most concerning clue in this set. If toxicity is suspected, clinicians would typically pause the infusion, monitor respiratory status, check reflexes, and measure serum magnesium levels.