Weighing the risks when treating hyponatremia
The risk of hyponatremia-associated complications must be balanced against the risk of serum sodium correction. Factors that should be considered before treating include the rapidity of onset of hyponatremia; degree, duration, and symptomatology of hyponatremia; and the presence or absence of risk factors for neurologic complications.1
Appropriate correction of hyponatremia
Hypotonic hyponatremia results in water entering the brain, leading to cerebral edema, intracranial hypertension, and a risk of brain injury. Within hours, however, solutes exit the brain tissues, inducing loss of water and relieving swelling of the brain. This adaptation process helps explain why even patients with severe hyponatremia may have few symptoms if the condition develops slowly.2
Nonetheless, the adaptation process may be associated with the rare but serious consequence of osmotic demyelination syndrome (ODS) if the rate of correction of sodium is too rapid. ODS can develop 1 to several days after aggressive treatment of hyponatremia (e.g., too rapid correction), even with water restriction alone. Shrinkage of the brain leads to demyelination of pontine and extrapontine neurons, which can cause neurologic dysfunction in the form of quadriplegia, pseudobulbar palsy, seizures, coma, or even death. Patients with hepatic failure, potassium depletion, and malnutrition are at increased risk of this complication.2
Adapted from Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000;342(21):1581-1589. Copyright © 2000 Massachusetts Medical Society. All rights reserved.
Treat hyponatremia appropriately to avoid ODS2
Although no consensus has been reached regarding the optimal treatment of symptomatic hyponatremia, experts advise that correction should be of sufficient rapidity and magnitude to reverse the manifestations of hypotonicity, but not be so rapid or large as to impose a risk of ODS.2 According to the most recent guidelines for treating hyponatremia, the rate of correction of hyponatremia should be limited to <10 to 12 mEq/L in 24 hours and <18 mEq/L in 48 hours.3
As always, physicians must use their clinical judgment when treating patients with hyponatremia.
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References:
- Douglas I. Hyponatremia: why it matters, how it presents, how we can manage it. Cleve Clin J Med. 2006;73(suppl 3):S4-S12.
- Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000;342(21):1581-1589.
- Verbalis JG, Goldsmith SR, Greenberg A, Schrier RW, Sterns RH. Hyponatremia treatment guidelines 2007: expert panel recommendations. Am J Med. 2007;120(11, suppl 1):S1-S21.
