CMAJ • June 22, 2004; 170 (13). doi:10.1503/cmaj.1040578.
© 2004 Canadian Medical Association or its licensors
All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association.
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Letters
Correspondance

Hyponatremia: terminology and more

Guy Decaux, Wim Musch and Alain Soupart

Erasmus University Hospital, Brussels, Belgium

As discussed by Karen Yeates and associates1 in their review of hyponatremia, evaluation of extracellular volume is sometimes difficult. In a patient with hyponatremia, a trial of saline infusion may be useful in clarifying the diagnosis; however, contrary to information in the review, most patients with SIADH will not experience worsening of hyponatremia after infusion of isotonic saline. We found that only 30% of 33 consecutive patients with SIADH had a decrease in plasma sodium levels after infusion of 2 L of isotonic saline over 24 hours;2 our observations were similar for patients with urine osmolality above 530 mOsm/L.3

Yeates and associates1 state that "hyponatremia should be corrected at a rate similar to that at which it developed," but this recommendation could be misleading. In the classical model used to induce osmotic demyelination syndrome in hyponatremic rats, initial serum sodium level was 142 mmol/L and decreased to 115 mmol/L after 24 hours, 113 mmol/L after 48 hours and 110 mmol/L after 72 hours.4 If the sodium level were to be corrected on the first day by 3 mmol/L, on the second day by 2 mmol/L and on the third day by 27 mmol/L, severe brain damage would develop, despite a correction rate similar to the rate of induction of hyponatremia. For the long-term management of SIADH in cases where water restriction is ineffective, we use demeclocycline, urea or furosemide, although immediate introduction of oral vasopressin V2 receptor antagonists may make management easier.5,6

Guy Decaux Wim Musch Alain Soupart Erasmus University Hospital Brussels, Belgium

Footnotes

Competing interests: None declared.


References

  1. Yeates KE, Singer M, Morton AR. Salt and water: a simple approach to hyponatremia. CMAJ 2004; 170(3):365-9. [Abstract/Free Full Text]
  2. Musch W, Decaux G. Utility and limitations of biochemical parameters in the evaluation of hyponatremia in the elderly. Int Urol Nephrol 2001; 32 (3): 475-93. [CrossRef][Medline]
  3. Musch W, Decaux G. Treating the syndrome of inappropriate ADH secretion with isotonic saline. Q J M 1998;91(11):749-53.
  4. Decaux G, Soupart A. Treatment of symptomatic hyponatremia. Am J Med Sci 2003;326 (1): 25-30. [CrossRef][Medline]
  5. Decaux G. Long-term treatment of patients with inappropriate secretion of antidiuretic hormone by the vasopressin receptor antagonist conivaptan, urea, or furosemide. Am J Med 2001;110 (7): 582-4. [CrossRef][Medline]
  6. Decaux G, Musch W, Soupart A. Hyponatremia in the intensive care: from diagnosis to treatment. Acta Clin Belg 2000;55(2):68-78.[Medline]




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