A patient admitted with dehydration secondary to prolonged diarrhea has a serum sodium level of 158 mEq/L. The patient appears restless and reports intense thirst. Vital signs show mild tachycardia. Which assessment is the nurse's priority?

A serum sodium of 158 mEq/L indicates severe hypernatremia. At this level, water moves out of neurons by osmosis, causing brain cells to shrink. This can result in cerebral irritability, confusion, seizures, and intracranial hemorrhage from torn bridging veins. The patient is already showing restlessness, an early neurological sign. Because neurological deterioration can be rapid and life-threatening, the nurse's priority assessment is neurologic status — level of consciousness, orientation, and neuromuscular signs such as tremors or seizures. Monitoring intake and output is important for tracking fluid balance and guiding rehydration, but it is not the immediate priority when neurological compromise is already evident. Peripheral edema is unlikely with hypernatremia from dehydration; the patient is volume-depleted. Skin turgor assessment is useful for confirming dehydration but does not identify the most dangerous complication. Neurological status directly reflects cerebral cellular integrity and must be assessed first to detect life-threatening deterioration.