A 45-year-old man develops severe hyponatremia (serum Na 118 mEq/L) over 48 hours with confusion. He is euvolemic on examination. Urine sodium is 55 mEq/L and urine osmolality is 480 mOsm/kg. Serum osmolality is 248 mOsm/kg. He was started on citalopram 6 weeks ago for depression. What is the maximum safe rate of sodium correction over the first 24 hours to prevent osmotic demyelination syndrome (ODS)?
- A Correct sodium by no more than 10–12 mEq/L in 24 hours ✓
- B Correct sodium by 20–25 mEq/L in 24 hours for rapid neurological improvement
- C Correct sodium by 15–20 mEq/L in the first 8 hours only
- D There is no correction limit if the patient is confused
Explanation
SIADH (euvolemic hyponatremia with elevated urine sodium and osmolality) caused by SSRIs (citalopram) requires careful sodium correction. To prevent osmotic demyelination syndrome (central pontine myelinolysis), the rate of correction must not exceed 10–12 mEq/L per day (some guidelines suggest 8–10 mEq/L in high-risk patients with chronic hyponatremia). Over-rapid correction removes the organic osmoles that brain cells have adapted to, leading to cerebral shrinkage and demyelination. Symptoms of ODS (dysarthria, dysphagia, spastic quadriplegia, locked-in syndrome) appear 2–6 days after overcorrection.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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