Why should hypernatremia be corrected gradually in hospitalized patients?

• A. To prevent hyponatremia
• B. To prevent seizures
• C. To prevent electrolyte derangements
• D. To avoid cerebral edema due to rapid osmolality shifts

Answer: (D)

Hypernatremia causes brain cells to shrink as water moves out to balance the high extracellular osmolality. The brain adapts by accumulating osmolytes to protect itself. If you correct sodium too quickly, the extracellular fluid becomes relatively hypoosmotic compared to the brain, and water rushed back into cells leads to cerebral edema and potential injury. By correcting gradually, the brain has time to readjust its osmolyte content and prevent swelling. In practice, aim for a slow correction (roughly 0.5 mEq/L per hour, not exceeding about 12 mEq/L in 24 hours) with careful monitoring. While preventing seizures or other electrolyte derangements can be important, the central reason for a gradual correction here is to avoid cerebral edema from rapid osmolality shifts.