Predictors of outcome in hospitalized patients with severe hyponatremia

Severe hyponatremia is associated with increased morbidity and mortality. Clinicians treating patients with severe hyponatremia are often torn between a desire to promptly raise serum sodium concentration to a "safe range," and at the same time, to avoid excessively rapid correction of hyponatremia. The aim of this study was to assess the prevalence of severe hyponatremia in hospitalized patients, the etiologic factors involved, as well as treatment and outcome of the patients using a retrospective case series.

Retrospective study of 168 patients with severe hyponatremia (< 115mmol/L) seen at Grady Memorial Hospital, a tertiary teaching hospital, in Atlanta, Georgia, from 1997-2001. The main outcome measures of interest were death during admission or occurrence of neurologic symptoms before, during or after therapy.

One hundred sixty-eight patients met the inclusion criteria out of a total of 5994 patients with hyponatremia treated at our hospital over the study period. Eighty-nine patients (52.9%) were symptomatic. The mean absolute serum sodium at 48-hours of therapy was 120.02 +/- 8.31 mmol/L. Respiratory failure and/or hypoxia was present in 28 patients (16.7%); sepsis was documented in 16 patients (9.5%). Mortality rate was high, 34 patients died (20.2%). On multivariate analysis factors with strong association with mortality of patients with severe hyponatremia were hypoxia, presence of neurologic symptoms, slow correction rates and a diagnosis of sepsis.

The mortality associated with severe hyponatremia remains high. Sepsis, respiratory failure and the presence of symptoms predict poor outcome in hospitalized patients with severe hyponatremia. More aggressive therapy with 3% saline may improve outcome in symptomatic patients. Our data suggest that a slow rate of correction in severe hyponatremia is associated with higher mortality than rapid correction, at least in the short-term.