A 64-year-old female presents with confusion, generalized seizures, and severe hyponatremia (serum sodium 108 mEq/L). What is the immediate treatment to stop neurological symptoms, and what is the maximum recommended rate of sodium correction over the first 24 hours to prevent osmotic demyelination syndrome (ODS)?

Answer and explanation

Correct answer: C. 100 mL bolus of 3% hypertonic saline; correct by no more than 8 mmol/L in 24 hours

  1. Step 1: Severe symptomatic hyponatremia (seizures, coma) is a medical emergency requiring rapid partial correction with 3% hypertonic saline (100 mL IV bolus over 10 minutes, repeated up to twice if symptoms persist) to raise serum sodium by 4-6 mmol/L and reduce cerebral edema.
  2. Step 2: However, the total sodium rise must NOT exceed 8 mmol/L in the first 24 hours (and <= 18 mmol/L in 48 hours).
  3. Step 3: Overly rapid correction causes central pontine myelinolysis / Osmotic Demyelination Syndrome (ODS), resulting in spastic quadriparesis, pseudobulbar palsy, and death.
Answer
100 mL bolus of 3% hypertonic saline; correct by no more than 8 mmol/L in 24 hours.
Why not the others: 'Correct by 20 mmol/L in 24 hours' causes devastating pontine myelinolysis and permanent brain damage; 'Free water oral intake' will worsen hyponatremic brain swelling and cause fatal uncal herniation; 'Furosemide without sodium' worsens hypovolemia.

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