What is osmotic demyelination in hyponatremia and how is it treated?

Updated: Dec 28, 2018
  • Author: Kartik Shah, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Answer

Chronic hyponatremia must be managed with extreme care. Treatment of chronic hyponatremia has been associated with the development of the osmotic demyelination syndrome (also known as central pontine myelinolysis) characterized by focal demyelination in the pons and extrapontine areas associated with serious neurologic sequelae.

The pathophysiology of osmotic demyelination is controversial. Multiple cohort studies and 3 reviews of the literature suggest that the syndrome is caused by overly rapid correction or overcorrection of chronic hyponatremia. [26] Some investigators note that osmotic demyelination often develops when chronic hyponatremia is complicated by hypoxia and believe that osmotic demyelination may be a form of hypoxic encephalopathy associated with hyponatremia and not a complication of therapy. [27] Until further data are available, management should include meticulous attention to adequate oxygenation and a gradual increase in serum sodium level to 120-125 mEq/L. Serum sodium level should not be allowed to reach normal levels or hypernatremic levels within the first 48 hours.

Symptoms of osmotic demyelination (eg, dysarthria, dysphagia, seizures, altered mental status, quadriparesis, hypotension) typically begin 1-5 days after correction of serum sodium level. [28]

The condition is typically irreversible and often devastating. Slow, cautious correction of serum sodium level and maintenance of adequate oxygenation in these patients is important.

Patients with hypokalemia, female gender, or history of alcoholism or liver transplant seem to be particularly prone to develop osmotic demyelination. [29] Exercise extreme caution in treating hyponatremia in these subgroups.

To minimize the risk of osmotic demyelination, older literature recommended correction of sodium in chronic hyponatremia at a rate no greater than 10-12 mEq/L in the first 24 hours. However, newer guidelines recommend a maximum of 8 mEq/L in the first 24 hours, with a maximum of 6 mEq/L for patients at high risk of osmotic demyelination. The authors will use the safer margin as our recommendation. [26]


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