Which IV therapy is used for severe hyponatremia (3%)?

• A. Hypertonic saline (3%) IV
• B. Normal saline
• C. Dextrose 5% in water
• D. Lactated Ringer's

Answer: (A)

Severe hyponatremia with neurologic symptoms requires a rapid but controlled rise in serum sodium to reduce brain swelling. Hypertonic saline, specifically 3% NaCl, does this by increasing extracellular osmolality, drawing water out of swollen brain cells and relieving cerebral edema. In symptomatic cases, clinicians often give a small bolus of 100 mL of 3% saline over about 10 minutes, and may repeat up to two more times based on response, aiming for roughly a 4-6 mEq/L increase in sodium within the first 24 hours. After the initial correction, continue careful monitoring of sodium and adjust the infusion to avoid overshoot, since too-rapid correction can cause osmotic demyelination syndrome. If the correction starts going too fast, steps can be taken to slow it down, including using desmopressin to limit free water loss.

Isotonic fluids like normal saline are not ideal for severe hyponatremia because they may not raise the sodium quickly enough and can potentially worsen the imbalance in certain patients. Dextrose-containing solutions provide free water, which can further dilute serum sodium, and lactated Ringer’s does not reliably correct hyponatremia.