A 60-year-old woman on hydrochlorothiazide develops serum sodium of 118 mEq/L over 3 days with progressive confusion. She is euvolaemic. Serum osmolality is 245 mOsm/kg, urine osmolality 580 mOsm/kg, and urine sodium 55 mEq/L. What is the most appropriate correction rate for sodium in chronic hyponatraemia to avoid osmotic demyelination syndrome (ODS)?
- A Correct rapidly at 2 mmol/L/hour until symptoms resolve
- B Correct to 130 mmol/L within 6 hours using 3% saline
- C Correct at 12 mmol/L per 24 hours maximum; if high-risk, target 8 mmol/L/day ✓
- D No limit; correct as fast as possible to prevent cerebral oedema
Correct answer: C. Correct at 12 mmol/L per 24 hours maximum; if high-risk, target 8 mmol/L/day
Explanation
In chronic hyponatraemia (>48 hours duration), the safe correction rate is ≤10–12 mmol/L in the first 24 hours and ≤18 mmol/L in 48 hours to prevent osmotic (central pontine) demyelination syndrome. High-risk patients (malnutrition, alcoholism, severe hypokalaemia, liver disease) should be corrected at ≤8 mmol/L/24 hours. This SIADH (urine osmolality > serum, high urine sodium, euvolaemia) from thiazide is chronic and should be managed cautiously. If overcorrection occurs, relowering sodium with hypotonic fluid and desmopressin is recommended to prevent ODS.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.