Overcorrection of severe hyponatremia, osmotic demyelination syndrome, and mortality: insights from two Brazilian centers

INTRODUCTION: Severe hyponatremia (sodium ≤ 120 mmol/L) poses significant clinical risks, including encephalopathy and seizures, but inadvertent rapid correction may cause osmotic demyelination syndrome (ODS). Current guidelines recommend limiting sodium correction to ≤8 mmol/L per 24 hours to minimize ODS risk. However, recent studies suggest that overcorrection may not directly contribute to mortality and could even be associated with improved outcomes. METHODS: This retrospective cohort study included 362 patients with severe hyponatremia admitted to two Brazilian tertiary hospitals. Overcorrection was defined as a serum sodium increase >8 mmol/L in 24 hours or >18 mmol/L in 48 hours. Multivariate logistic regression and propensity score-weighted analyses were used to identify predictors and outcomes associated with overcorrection. RESULTS: Overcorrection occurred in 38.7% of patients whereas ODS occurred in only one patient (0.28%). Independent predictors of overcorrection included younger age, lower admission sodium levels, and higher volumes of 0.9% NaCl administered in the emergency room; cancer diagnosis and furosemide use were protective factors. Overcorrection was associated with lower in-hospital mortality and shorter hospital stays, even in propensity score-weighted multivariate analyses. However, a detailed review of mortality cases revealed no direct causal link between the rate of sodium correction and death. CONCLUSION: Overcorrection of severe hyponatremia was common and associated with better clinical outcomes, without a significant increase in the risk of ODS. However, given the observational nature of this association, randomized controlled trials are needed before the current guidelines for correction rate can be reconsidered.