Dysnatremia on intensive care unit admission is a stronger risk factor when associated with organ dysfunction

Dysnatremia present at the time of intensive care unit (ICU) admission is associated with mortality. In this study, we investigated the epidemiology of dysnatremia present on ICU admission and the impact of organ dysfunction on the association between dysnatremia and mortality. We hypothesized that dysnatremia comorbid with organ dysfunction is associated with higher risk of mortality.

This retrospective study was conducted on all patients admitted to the International Hospital General ICU in Istanbul over a period of 6 years (2006-2011). Patients were classified, according to the most abnormal serum sodium values measured within 24 hours after ICU admission, into 7 groups as follows: normonatremia (135≤Na≤145 mmol/L), borderline hyponatremia (130≤Na<135 mmol/L), mild hyponatremia (125≤Na<130 mmol/L), severe hyponatremia (Na <125 mmol/L), borderline hypernatremia (145155 mmol/L).

The total admitting patient were 1657. A total of 1060 patients' data were analyzed in this study. Sodium levels were normal in 637 (60.1%), hyponatremic in 367 (34.6%) and hypernatremic in 56 (5.3%) patients. Multivariate analysis showed that only SAPS II was associated with increased mortality (OR, 1.05 [95% confidence interval, 1.02-1.09]). The odds ratio (95% CI) of dysnatremia (Na <125 mmol/L and >150 mmol/L) for mortality was 4.37 (2.29-8.36) in patients with organ dysfunction (number of dysfunctional organs ≥1) (P<0.001).

Below 125 and above 150 mmol/L sodium levels at ICU admission are risk factors for higher mortality rates in patients with comorbid organ dysfunction. The effect of dysnatremia on mortality is observed when organ dysfunction is present.