Severity-Stratified Hyponatremia Is Associated with Increased Mortality and Complications in Nontraumatic Intracerebral Hemorrhage

Introduction: Hyponatremia is common after nontraumatic intracerebral hemorrhage (ICH) and has been associated with worse outcomes, although prior studies have been limited by smaller sample sizes and heterogeneous exposure definitions. This study evaluated the association between severity-stratified hyponatremia and mortality, survival, and complication rates following nontraumatic ICH. Methods: A retrospective cohort study was performed using the TriNetX database. Patients with nontraumatic ICH were stratified by serum sodium measurements obtained within 7 days of diagnosis. Two separate propensity score-matched analyses were conducted: moderate hyponatremia versus normonatremia (17,547 patients per cohort) and severe hyponatremia versus normonatremia (5010 patients per cohort). The primary outcome was 30-day mortality. Secondary outcomes included seizures, cerebral edema, hydrocephalus, external ventricular drain placement, tracheostomy, percutaneous endoscopic gastrostomy (PEG) placement, pulmonary embolism, deep vein thrombosis, ischemic stroke, and myocardial infarction. Statistical significance was set at p < 0.05. Results: Moderate hyponatremia was associated with increased 30-day mortality (17.5% vs. 13.3%; HR 1.324, 95% CI 1.255–1.398; p < 0.001), while severe hyponatremia demonstrated a greater increase in mortality (18.7% vs. 12.9%; HR 1.473, 95% CI 1.332–1.628; p < 0.001). Both cohorts had higher rates of seizures, cerebral edema, hydrocephalus, tracheostomy, PEG placement, deep vein thrombosis, and myocardial infarction compared with matched normonatremic controls. External ventricular drain placement was also more frequent in both cohorts. Pulmonary embolism increased in moderate hyponatremia but was not significantly different in severe hyponatremia. Ischemic stroke occurred less frequently in both cohorts. Conclusions: Moderate and severe hyponatremia were associated with increased mortality and complications in patients with nontraumatic ICH, with stronger associations observed in severe hyponatremia. These findings support serum sodium as a clinically relevant marker for risk stratification and monitoring during acute ICH care. However, causality cannot be established, and whether correction of hyponatremia improves outcomes requires prospective studies.