Increased short-term and long-term mortality in community- and hospital-acquired hypernatraemia and in patients with delayed serum sodium correction

Background This study examined the short-term and long-term mortality of community- and hospital-acquired hypernatraemia in a large cohort of general hospitalised patients, and the impact of delayed serum sodium correction in hypernatraemic patients. Methods Adult patients admitted to Mayo Clinic Rochester from 2011 to 2013 were examined. The patients with admission serum sodium >= 138 mEq/L and at least 2 serum sodium measurements during hospitalisation were included. Hypernatraemia was defined as serum sodium >= 143 mEq/L. The patients were categorised into three groups based on serum sodium at admission and during hospitalisation: (a) normal serum sodium, (b) community-acquired hypernatraemia and (c) hospital-acquired hypernatraemia. Outcomes included hospital mortality and 1-year mortality after hospital discharge amongst hospital survivors. Results Of 25 781 eligible patients, 45% had normal serum sodium, 20% had community-acquired hypernatraemia and 35% had hospital-acquired hypernatraemia. In adjusted analysis, odds ratios (ORs) of community- and hospital-acquired hypernatraemia for hospital mortality were 4.91 (95% CI 3.47-6.94) and 4.11 (95% CI 2.94-5.73), whereas hazard ratio (HR) for 1-year mortality was 1.76 (95% CI 1.56-1.98) and 1.61 (95% CI 1.45-1.79), respectively. Hospital-acquired hypernatraemia had a higher hospital mortality but not 1-year mortality than community-acquired hypernatraemia. In patients with community-acquired hypernatraemia, 36% remained hypernatraemic by hospital day 3. Hospital mortality (OR 3.01; 95% CI 2.71-5.83) and 1-year mortality (HR 1.51; 95% CI 1.26-1.81) were significantly increased in patients with persistent hypernatraemia, compared with those with serum sodium correction into optimal range of 138-142 mEq/L. Conclusion Hypernatraemia, regardless of acquisition origin, is associated with elevated short-term and long-term mortality. Hospital-acquired hypernatraemia was more common and had a higher short-term mortality than community-acquired hypernatraemia. Failure to correct hypernatraemia by hospital day 3 is associated with increased mortality.