Hyponatremia: Evidence‑Based Clinical Implications

Emergency Management

Patients with serum sodium < 125 mmol/L who exhibit severe neurological symptoms (altered mental status, seizures, or coma) should be transferred immediately to an intensive‑care unit and treated with 3 % hypertonic saline. 1

Hospital mortality is increased approximately 60‑fold in patients whose serum sodium falls below 130 mmol/L compared with normonatremic patients (11.2 % vs 0.19 %). 2, 3
When serum sodium is < 120 mmol/L, in‑hospital mortality rises to 25 % versus 9.3 % in patients with sodium > 120 mmol/L. 2, 3
A mean serum sodium of 125.3 mmol/L is linked to a 7‑fold higher likelihood of dying during the hospital stay and a two‑fold higher likelihood of death after discharge. 2, 3

The severity of hyponatremia does not consistently predict symptom presence; for example, a patient with a sodium level of 126 mmol/L may experience falls despite having only “moderate” laboratory values. 2, 3

For patients with mild hyponatremic symptoms, an initial fluid restriction of 1 L per day is recommended as first‑line therapy. 4

If serum sodium does not improve after fluid restriction, add oral sodium chloride (approximately 100 mEq three times daily) to promote correction. 4

In symptomatic patients, serum sodium should be measured every 4 hours during the initial treatment phase to detect rapid changes. 4

Do not exceed a rise of 8 mmol/L in 24 hours when correcting mild chronic hyponatremia, to avoid osmotic demyelination syndrome. 4
For chronic hyponatremia lasting longer than 48 hours, the correction rate should be less than 1 mmol/L per hour. 4