Predialysis hypernatremia is a prognostic marker in acute kidney injury in need of renal replacement therapy.

BACKGROUND AND OBJECTIVES: The present study aimed to evaluate the prognostic impact of predialysis dysnatremia in patients with acute kidney injury requiring renal replacement therapy (RRT). DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: A secondary analysis of a prospective multicenter cohort study was performed. Serum sodium (Na) concentrations were categorized immediately before the first RRT as normonatremia (135≤Na ≤145mEq/L), hyponatremia (mild [130≤Na ≤134mEq/L] or severe [Na ≤129mEq/L]), and hypernatremia (mild [146≤Na ≤155mEq/L] or severe [Na ≥156mEq/L]). Multivariable logistic regression was used to estimate the impact of sodium levels categories on hospital mortality. RESULTS: Dysnatremia occurred in 47.3% of 772 included patients. Hypernatremia was more frequent than hyponatremia (33.7% vs 13.6%, P=.001). Intensive care unit (ICU) and hospital mortality rates were 64.6% and 69%, respectively. Hospital mortality was higher in severe hypernatremia (89.1% [95% confidence interval {CI}, 78.7%-95.8%] vs 64.6% [CI, 59.8%-69.2%], P<.001, in normonatremia). Older patients, clinical admission, number of comorbidities, length of ICU stay before the beginning of RRT, and the number of organ dysfunctions were associated with higher hospital mortality. In multivariate analysis, severe hypernatremia (odds ratio, 2.87; 95% CI, 1.2-6.9), poor chronic heath status, severity of illness, sepsis, and lactate were independently associated with outcome. CONCLUSION: Almost 50% of patients with acute kidney injury in need of RRT in the ICU had mild or severe dysnatremia before dialysis initiation. Hypernatremia was the main sodium disturbance and independently associated with poor outcome in the study population.