A 32-year-old pregnant woman at 28 weeks gestation presents to the prenatal clinic with complaints of severe headaches, visual disturbances, and epigastric pain. Her blood pressure is 160/110 mmHg, and urinalysis shows 3+ proteinuria. Which assessment finding would be most concerning and require immediate intervention?

In patients with severe preeclampsia, the neurological examination is critical. Hyperreflexia with sustained clonus is the most reliable clinical indicator of severe CNS irritability and imminent eclampsia. Assess deep tendon reflexes at every encounter, specifically looking for more than three beats of clonus at the ankle. This finding represents a failure of cerebral autoregulation and precedes seizure activity.

• Initiate seizure precautions: pad side rails, ensure suction and oxygen are at the bedside, and keep the bed in the lowest position.
• Notify the provider immediately and prepare to administer magnesium sulfate as ordered. A typical loading dose is 4-6 g IV over 15-20 minutes, followed by a maintenance infusion of 1-2 g/hour.
• Monitor for magnesium sulfate toxicity: assess patellar reflexes hourly, monitor respiratory rate (must be >12/min), and check urine output (must be >30 mL/hour). Have calcium gluconate readily available as an antidote.

While ankle edema, mild headache, and elevated blood pressure are common in preeclampsia, they do not carry the same immediate threat as hyperreflexia with clonus. A headache that is severe, unrelenting, or unresponsive to analgesia, combined with visual disturbances, also warrants urgent evaluation. Epigastric or right upper quadrant pain signals hepatic capsular stretch and is another severe feature requiring prompt intervention.