A 60-year-old man develops severe hyponatraemia (serum Na 112 mEq/L) after elective hip replacement. He is symptomatic with confusion and mild seizures. What is the correct initial rate of sodium correction to prevent osmotic demyelination syndrome (ODS) while treating acute symptoms?

• A Give 3% hypertonic saline as a 150 mL bolus IV over 20 minutes, targeting 5 mEq/L rise in first 1 hour; total correction ≤ 10-12 mEq/L in first 24 hours ✓
• B Correct at 12-15 mEq/L in the first 24 hours — faster correction is safe and needed in surgical patients
• C Correct slowly at 1 mEq/L per hour maximum regardless of symptoms
• D Oral water restriction alone — IV treatment contraindicated in post-surgical setting

Explanation

In acute symptomatic hyponatraemia with seizures/severe neurological symptoms, the priority is to achieve a rapid initial rise of 5 mEq/L in the first 1 hour using 150 mL boluses of 3% hypertonic saline (repeatable if no improvement). However, total correction must not exceed 10 mEq/L in the first 24 hours and 18 mEq/L in 48 hours to prevent osmotic demyelination syndrome (ODS / central pontine myelinolysis). The acute correction relieves cerebral oedema; over-rapid total correction strips myelin in pontine oligodendrocytes. If overcorrection occurs, relowering sodium with DDAVP and D5W is recommended.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.