A post-operative patient in surgical ICU has a serum sodium of 128 mEq/L. Review of his fluid chart shows he has received 3 litres of 5% dextrose since the operation. His urine sodium is 40 mEq/L and osmolality is 280 mOsm/kg. He is asymptomatic but the team is planning correction. What is the maximum safe rate of sodium correction per 24 hours to avoid central pontine myelinolysis?
- A Up to 6 mEq/L per 24 hours
- B Up to 20 mEq/L per 24 hours
- C Up to 10–12 mEq/L per 24 hours ✓
- D Up to 3 mEq/L per hour until normalised
Correct answer: C. Up to 10–12 mEq/L per 24 hours
Explanation
Overly rapid correction of chronic hyponatraemia risks osmotic demyelination syndrome (central pontine myelinolysis). Safe correction is limited to 10–12 mEq/L per 24 hours (or ≤18 mEq/L per 48 hours) in chronic hyponatraemia. In acute symptomatic hyponatraemia, a rapid initial bolus of 2–3 mEq/L over 20–30 minutes (hypertonic saline) is allowed for seizure cessation, but then the 10–12 mEq/day limit applies.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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