Frequency of Hyper- and Hypo-natremia in Patients admitted in the ICU & comparison of their association with mortality

Backgraound: Sodium disturbances are among the most common electrolyte disturbance in Intensive Care Unit (ICU) patients. The aim of the present study was to determine the frequency of hypernatremia, hyponatremia and their comparison in relation to their mortality impact on patients admitted to a general ICU.

In a cross sectional fashion we studied 273 patients hospitalized in an ICU of a large teaching hospital in Tehran, Iran between 2004 and 2006. Age, sex, reasons for hospitalization, hyponatremia (serum sodium < 135 mEq/L) and hypernatremia (serum sodium > 145 mEq/L) during ICU stay were recorded and their effects on ICU mortality of the patients were assessed.

We observed hypernatremia in 39.5% and hyponatremia in 60.5% of our patients. The mean age of patients with serum sodium imbalance was significantly higher as compared to those without it 52±21 vs. 44±20 years for hyponatremics and 56±20 vs. 49±22 years for hypernatremics respectively. Hyponatremia occurred more frequently in surgical patients than those with medical causes, 72% vs. 22% respectively. Mortality of patients with hyponatremia (34% vs. 15% with odds ratio of 5.7 and 95% CI from 2.9 to 11.30) and hypernatremia (55.2% vs. 17.8% with odds ratio of 2.8 and 95%CI from 1.4 to 5.5) were significantly higher than patients without sodium imbalance. 55%with hypernatremia died vs. 34% with hyponatremia, (95% CI from 7.7% to 33.9%, p value = 0.0034).

Serum sodium imbalances are frequent in ICU patients, occurring more frequently in older individuals and are associated with an unacceptably high mortality. Mortality was significantly higher in patients with hypernatremia compared to those with hyponatremia.