In magnesium sulfate therapy for preeclampsia, which symptom indicates a potential toxicity risk?

The presence of absent patellar reflexes in a patient receiving magnesium sulfate therapy for preeclampsia signals a potential risk of magnesium toxicity. Magnesium sulfate is often used in the management of severe preeclampsia and eclampsia to prevent seizures, but it must be administered with caution due to its effects on the neuromuscular system.

The patellar reflex is a deep tendon reflex that can be monitored to assess neuromuscular function. A diminished or absent reflex indicates that the medication may have reached toxic levels, potentially leading to further neuromuscular impairment and adverse outcomes. In practice, healthcare providers routinely check deep tendon reflexes to monitor for toxicity and ensure the safety of the patient.

While the other symptoms listed, such as visual disturbances, decreased urine output, and hypotonicity, could also signal issues related to magnesium or the underlying condition, the absence of the patellar reflex serves as a direct and clear indication of neuromuscular compromise due to magnesium sulfate, hence highlighting a more immediate concern regarding toxicity. Monitoring this reflex is a standard part of care for patients receiving magnesium sulfate, making it a crucial indicator in assessing the risk of toxicity.