Burden of sodium abnormalities in patients hospitalized for heart failure

Hyponatremia presumably is associated with adverse clinical outcomes in patients with congestive heart failure (CHF), but risk thresholds and economic burden are less studied. The authors analyzed 115,969 patients hospitalized for CHF and grouped them by serum sodium levels (severe hyponatremia, ≤130 mEq/L; hyponatremia, 131-135 mEq/L; normonatremia, 136-145 mEq/L; hypernatremia, >145 mEq/L). Univariable and multivariable analyses on the associated clinical and economic outcomes were performed. The most common abnormality was hyponatremia (15.9%), followed by severe hyponatremia (5.3%) and hypernatremia (3.2%). Hospital mortality was highest for severe hyponatremia (7.6%), followed by hypernatremia (6.7%) and hyponatremia (4.9%) (P<.0001). Compared with normonatremia, risk-adjusted mortality was highest for severe hyponatremia (odds ratio [OR], 1.78; 95% confidence interval [CI], 1.59-1.99), followed by hypernatremia (OR, 1.55; 95% CI, 1.34-1.80) and hyponatremia (OR, 1.29; 95% CI, 1.19-1.40; all P<.0001). Risk-adjusted hospital prolongation was greater for each level of sodium abnormality than for normonatremia, ranging from 0.42 (CI, 0.26-0.60) days for hypernatremia to 1.28 (CI, 1.11-1.47) days for severe hyponatremia. Risk-adjusted attributable hospital cost increase was highest for severe hyponatremia ($1132; CI, $856-$1425; all (P<.0001). Sodium abnormalities were common in patients hospitalized for CHF. Adverse outcomes resulted not only from severe hyponatremia, but also from mild hyponatremia and hypernatremia.