Clinical question: Of the patients who are admitted with hyponatremia, how many develop osmotic demyelination syndrome (ODS)?
Background: ODS is a rare but serious complication associated with hyponatremia. Previous studies demonstrated rates of ODS that ranged from 0.28 to 0.5%, with rapid sodium correction occurring in the majority but not all patients with ODS. Guidelines recommend slowly correcting serum sodium by no more than 8 mmol/L in 24 hours. Because there can be drawbacks associated with this approach, this study sought to further characterize the proportion of ODS in patients hospitalized with hyponatremia.
Study design: Multicenter cohort study
Setting: Patients hospitalized with hyponatremia in five Toronto academic hospitals between April 1, 2010 and December 31, 2020
Synopsis: The study included 22,858 hospitalizations of adult patients with hyponatremia admitted to general internal medicine or intensive care. Hyponatremia was defined as a serum sodium <130 mmol/L. The mean initial sodium was 125 mmol/L (standard deviation, 4.6). Rapid correction of serum sodium was defined as an increase of greater than 8 mmol/L in any 24-hour period, which occurred in 3,632 admissions (17.7%). Patients with possible ODS were identified using the results of neuroimaging and chart review. Twelve patients developed definite or probable ODS (0.05%), and of those, seven developed ODS in the absence of rapid sodium correction (58%). The rate of ODS was likely lower than in previous studies because patients with higher initial sodium levels were included.
A limitation of this study is the rarity of ODS, which makes it difficult to obtain adequate power to comment on possible affecting factors.
Bottom line: Rapid serum sodium correction was common and ODS was extremely rare. Studies with a higher number of patients with ODS are needed to better understand causal factors.
Citation: MacMillan TE, et al. Osmotic demyelination syndrome in patients hospitalized with hyponatremia. NEJM Evidence. 2023;2(4). Doi:10.1056/evidoa2200215
Dr. Mohoney is an internal medicine resident, PGY-3, at Maine Medical Center, Tufts University School of Medicine in Portland, Maine.