Revisiting New Data on the Mortality Benefit of Rapid Correction of Hyponatremia: Déjà vu All Over Again.

Studies in the 1980s linking rapid correction of severe, chronic hyponatremia to the osmotic demyelination syndrome (ODS) led to a major controversy that eventually gave way to consensus guidelines. Efforts to limit correction to ≤8 mmol/L per day in patients at high risk of developing ODS became common practice. Recent studies have questioned these guidelines, suggesting that ODS is rare and that slow correction may increase mortality. In this review, we revisit the history of the controversy and find that these claims have persisted for four decades. Older studies supporting faster correction are flawed by referral bias while newer studies are limited by confounding as comorbidities influence rates of both mortality and hyponatremia correction. While both old and new studies emphasize the rarity of MRI-documented ODS after rapid correction, they were not conducted in hyponatremic patients who were at risk for ODS. Old studies reporting hyponatremic deaths due to cerebral edema overestimate its true incidence and new studies reporting an association of mortality and slow rates of sodium correction do not document cerebral edema as a common contributor to death. Further research is required to better define the incidence of both ODS and cerebral edema in patients at risk for these complications. Until then, we conclude that the risks of rapid correction-including irreversible neurological damage-necessitate caution. Clinicians should continue to prioritize slow, controlled sodium correction to protect high-risk patients from harm.