Risk Factors for Neurological Symptoms in Hyponatraemic Patients: A Retrospective Cohort Study

Background and Hypothesis Hyponatraemia is one of the most common electrolyte disorders. While hyponatraemia can cause severe neurological symptoms, its clinical predictors remain poorly defined. This study aimed to identify factors associated with neurological involvement in patients with severe hyponatraemia. Methods This retrospective cohort study included patients with severe hyponatraemia (serum sodium level ≤120 mEq/l) at admission or during hospitalisation between January 2014 and June 2024 in two tertiary centres. Neurological symptoms were defined as vomiting, deep somnolence, seizures, coma, or cardiopulmonary arrest. Risk factors were evaluated using multivariable logistic regression analysis. Results Among 834 patients included in the analysis, the median (interquartile range) age was 73 (62–82) years, 382 (46%) were female, and the median serum sodium level was 118 (116–119) mEq/l. Neurological symptoms were observed in 221 (26%). Low serum potassium (<4.0 mEq/l; OR, 1.53; 95% CI, 1.05–2.23) was independently associated with an increased risk of neurological symptoms, together with low serum sodium (<115 mEq/l; OR, 2.23; 95% CI, 1.49–3.33). Compared with chronic onset, both acute onset (OR, 3.92; 95% CI, 2.36–6.51) and uncertain onset (OR, 2.05; 95% CI, 1.40–2.99) also showed significant association with their occurrence. Conclusion Low serum potassium, low serum sodium, and onset pattern were independent predictors of neurological symptoms in patients with severe hyponatraemia. Particularly in those with these risk factors, careful assessment and individualised management of sodium imbalance may be appropriate to achieve favourable outcomes.