Intensive care unit–acquired hypernatremia is an independent predictor of increased mortality and length of stay

Abstract Purpose The purpose of this study is to examine the impact of hypernatremia acquired after intensive care unit (ICU) admission on mortality and length of stay (LOS). Materials and Methods Data for this observational study were collected from patients admitted between January 1, 2008, and September 30, 2010 to 344 ICUs in the eICU Research Institute. Results Of the 207 702 eligible patients, 8896 (4.3%) developed hypernatremia (serum Na > 149 mEq/L). Hospital mortality was 32% for patients with hypernatremia and 11% for patients without hypernatremia ( P < .0001). Intensive care unit LOS was 13.7 ± 9.7 days for patients with hypernatremia and 5.1 ± 4.6 for patients without hypernatremia ( P < .0001). Multivariate analysis showed that hypernatremia was an independent risk factor for hospital mortality with a relative risk (RR) of 1.40 (95% confidence interval, 1.34-1.45) and ICU LOS with a rate ratio (RtR) of 1.28 (1.26-1.30). The RR for mortality and RtR for ICU LOS increased with increasing severity strata of hypernatremia, but the duration of hypernatremia was not associated with mortality. Conclusions Hypernatremia developed following ICU admission in 4.3% of patients. Hypernatremia was independently associated with a 40% increase in risk for hospital mortality and a 28% increase in ICU LOS. Severity, but not duration of ICU-acquired hypernatremia was associated with hospital mortality.