Osmotic Demyelination Syndrome
Presenter: Richard Sterns, MD (Rochester Medical Center)
Dr. Sterns started his lecture with the risk factors for osmotic demyelination syndrome (ODS): 1) chronic hyponatremia, 2) malnutrition, 3) hypokalemia, 4) serum [Na+] less than 105 meq/l, 5) too fast a correction of hyponatremia. Interestingly and perhaps frightening, the clinical symptomatology and radiographic findings of ODS are delayed by 2–3 days. Thus one gets the impression of clinical improvement while, in reality, the situation is deteriorating towards ODS. He did not focus on any earlier warning signs/symptoms of ODS.
Where did the 1 meq/l/hour correction of [Na+] come from? Evidence shows that a correction of 2.8 meq/l/hour portends a 20% risk of ODS, while 1 meq/l/hour portends less than 5% risk.
Thus far, the only effective management of ODS (other than prevention) is to reinitiate hyponatremia using free water with or without dDAVP infusions. Studies from Sugumura in Japan initially showed some therapeutic effect against ODS using dexamethasone (of note, recent data from this group suggests minocycline may have a therapeutic effect as well).
Finally, how does hypokalemia induce ODS? This question was only superficially answered — K+ infusions in hypokalemic patients will cause a rapid intracellular shift of that K+. This occurs at the expense of Na+ exiting the cells. In effect, K+ infusions increase serum [Na+], and since this can’t be controlled or regulated tightly, there is a risk of rapid [Na+] correction resulting in ODS.