Which symptom would most likely be observed in a patient with hypernatremia?

In a patient with hypernatremia, dry mucous membranes are a prominent symptom due to the excess sodium concentration in the blood which leads to cellular dehydration. When sodium levels rise, the osmolarity of the extracellular fluid increases, drawing water out of cells and tissues. This dehydration can result in decreased moisture in the mucous membranes, making them dry and less effective in producing secretions.

Dry mucous membranes are commonly observed as a physical sign in clinical assessments, as they indicate fluid loss and potential dehydration. This condition often accompanies other symptoms related to fluid imbalance, such as thirst, lethargy, or irritability, but the dryness of mucous membranes is a direct indicator of hypernatremia's effects on body hydration status.

In contrast, severe muscle spasms, convulsions, and increased reflexes can occur in various neurological and electrolyte imbalances but are not as specific or commonly associated with hypernatremia as dry mucous membranes are.