Incidence and prognosis of dysnatraemia in critically ill patients: Analysis of a large prevalence study

Background: The objective of this study is to assess the impact of dysnatraemia on mortality among intensive care unit (ICU) patients in a large, international cohort. Material and methods: Analysis of the Extended Prevalence of Infection in Intensive Care (EPIC II) study, a 1-day (8 May 2007) worldwide multicenter, prospective point prevalence study. Hyponatraemia was categorized as mild (130-134 mM/L), moderate (125-129 mM/L) or severe (< 125 mM/L). Hypernatraemia was also categorized as mild (146-150 mM/L), moderate (151-155 mM/L) or severe (> 155 mM/L). Patients with normal serum sodium (135-145 mM/L) constituted the reference group. The main outcome was hospital mortality. Analysis was conducted separately for patients admitted on the study day (25·8%) and those already present on the ICU (74·2%). Results: Serum sodium was measured in 13 276 of the 13 796 patients (96·2%). A total of 3815 patients (28·7%) had dysnatraemia: 12·9% with hyponatraemia and 15·8% with hypernatraemia. The prevalence of dysnatraemia was significantly greater in patients already present on the ICU prior to the study day than for those just admitted (13·1% vs. 12·3% for hyponatraemia and 17·1% vs. 12·1% for hypernatraemia, both P < 0·001). Hospital mortality rates were higher in patients with dysnatraemia than in those with normal sodium levels and were directly related to the severity of hypo- and hypernatraemia. This association between dysnatraemia and mortality was similar in infected and noninfected patients (P = 0·061). Conclusions: Dysnatraemia is more frequent during the ICU stay than on the day of admission. Dysnatraemia in the ICU - even mild - is an independent predictor of increased hospital mortality.

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