Severe symptomatic hyponatremia should be treated with which solution?

• A. Isotonic saline (0.9%)
• B. Hypertonic saline (3%)
• C. Dextrose 5% in saline
• D. Fluid restriction

Answer: (B)

Severe symptomatic hyponatremia causes brain swelling because the blood is too dilute, so the first priority is to rapidly raise the serum sodium to reduce cerebral edema and prevent life-threatening complications. Hypertonic saline works by increasing extracellular osmolality, which draws water out of swollen brain cells and quickly relieves pressure. In this urgent setting, small, controlled boluses of a concentrated saline solution (about 3% NaCl) are given, with the goal of producing a rapid but limited rise in sodium—roughly 4–6 mEq/L in the first few hours and clinical improvement of symptoms. After stabilization, correction proceeds more slowly and is closely monitored to avoid overcorrection, which can cause osmotic demyelination syndrome.

Dextrose-containing fluids (like D5W) provide free water after the glucose is metabolized, which can worsen hyponatremia. Isotonic saline may not correct the problem and can even worsen sodium levels in certain hyponatremic states (for example, SIADH). Fluid restriction is a long-term management strategy for nonurgent, chronic hyponatremia, not the initial treatment of severe symptoms.