Osmotic demyelination syndrome after correction of chronic hyponatremia with normal saline

Rapid correction of severe chronic hyponatremia with hypertonic saline has been known to cause osmotic demyelination syndrome (ODS). Less recognized are the dangers of rapid correction with normal saline. A 60-year-old woman on thiazide diuretics for hypertension presented with profound hyponatremia (94 mmol/L) and hypokalemia (1.9 mmol/L) associated with volume depletion. Normal saline (2 L/day) and (KCl 40 mmol/day) were given for 5 days. Serum Na+ concentration rose to 106 mmol/L within 18 hours. With improvement of her hyponatremia, she became more alert although the hypokalemia persisted. However, she developed progressive obtundation, quadriplegia, and respiratory failure 6 days later. Magnetic resonance imaging of the brain clearly showed typical features of pontine and extrapontine myelinolysis. We suggest that the aggressive KCl supplement would have been the first-line therapy for this patient presenting with chronic hyponatremia and hypokalemia associated with volume depletion.