Narrative ReviewHyponatremia and Mortality: Moving Beyond Associations
Section snippets
Complications of Hyponatremia
In a single issue in June 1986, the New England Journal of Medicine published 2 seminal articles on the complications of hyponatremia.6, 7 The study by Arieff6 reported the development of acute hyponatremia after elective surgery in 15 previously healthy women. Their average serum sodium level decreased from 138 to 108 mEq/L and was accompanied by grand mal seizures and respiratory arrest. Four women died and 9 were left in a persistent vegetative state. In most of these women, acute
Hospitalized Patients
Over the years, several studies have reported the outcome of hospitalized patients with hyponatremia (Table 1). In 1976, Arieff et al20 were some of the first to do so; the authors systematically studied the neurologic complications of hyponatremia in a selected cohort of 66 patients. They found that patients with acute hyponatremia were symptomatic significantly more often than those with chronic hyponatremia and that they had a mortality rate of 50%. Some patients with chronic hyponatremia
Possible Mechanisms of the Hyponatremia-Mortality Association
Previously, we proposed 3 possible scenarios to explain the association between hyponatremia and mortality (Fig 2).33 First, acute hyponatremia can contribute directly to mortality when there is progressive cerebral edema without timely intervention. Although it remains extremely important to recognize and treat this entity, as noted, it is unlikely to explain the overall association between hyponatremia and mortality. In the second scenario, hyponatremia is merely a surrogate marker for the
Conclusion
Hyponatremia increasingly is being recognized as an independent predictor of mortality. Prospective studies are necessary to determine whether hyponatremia in itself contributes to mortality and whether correcting hyponatremia improves outcomes. Mechanistically, the effects of hyponatremia on organs other than the brain should be a focus of research (Box 1). Until such studies are available, the presence of hyponatremia should be regarded as a risk factor for adverse outcomes and patients
Acknowledgements
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Financial Disclosure: The authors declare that they have no relevant financial interests.
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Originally published online January 7, 2013.