A 58-year-old man with a serum sodium of 116 mEq/L, severe confusion, and grand-mal seizures is brought to the emergency. He has polydipsia and dilute urine (osmolality 95 mOsm/kg). The diagnosis is psychogenic polydipsia. What is the maximum safe rate of sodium correction in the first 24 hours?
- A No more than 6–8 mEq/L in the first 24 hours to avoid osmotic demyelination syndrome
- B An initial rapid correction of 4–6 mEq/L over 1–2 hours is acceptable in severe symptomatic hyponatraemia, then limit total to 8–10 mEq/L in 24 hours ✓
- C Correct fully to 135 mEq/L within 6 hours using 3% saline + furosemide
- D Correction rate is irrelevant in psychogenic polydipsia as the mechanism prevents osmotic demyelination
Explanation
Current EAN/ESE 2014 and EASL guidelines for severe symptomatic hyponatraemia (seizures, severe confusion) recommend an initial rapid correction of 4–6 mEq/L (sometimes up to 5 mEq/L over the first hour with 150 mL of 3% saline) to control acute neurological symptoms, followed by a maximum total correction of 8–10 mEq/L in 24 hours and 18 mEq/L in 48 hours to prevent osmotic demyelination syndrome (ODS/CPM). Psychogenic polydipsia patients are at particularly HIGH risk of ODS if corrected too rapidly because their cells have had time to lose osmolytes (idiogenic osmoles). Full correction to normal sodium within 6 hours is dangerous.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.