Dysnatremia in hospitalized elderly patients

Dysnatremia is the most common electrolyte disorder in hospitalized patients; it encompasses hyponatremic and hypernatremic conditions. It is a common finding at Intensive Care Unit (ICU) admission [1-3]. Up to one third of critically ill patients have dysnatremia at ICU admission [2]. Another one-third of critically ill patients will develop an ICU-acquired dysnatremia during ICU stay [4,5]. Prevalence of dysnatremia at ICU admission, however, varies greatly according to the chosen definition [1,2,6,7]. Hyponatremia is a pathologic condition defined as a serum sodium < 135 mmol/L. It is the most common electrolyte disorder in hospitalized patients. Up to 40% of the overall population of hospitalized patients has a hyponatremia at admission [8]. Presence of severe hyponatremia on hospital admission has been demonstrated to be independently associated with an increased risk for ICU admission and poor prognosis [9]. Hyponatremia may be due to chronic organ dysfunctions (that is heart failure or liver dysfunction) but also to diuretic use, syndrome of inappropriate antidiuretic hormone (ADH) secretion, adrenal insufficiency, and cerebral or renal salt wasting syndromes [10,11]. Hypernatremia is defined as a serum sodium > 145 mmol/L. It is generally related to water losses with increase of plasma osmolality. Serum sodium is the main cation of extracellular fluid and plays a key role in serum osmolarity. It is less frequent than hyponatremia [10] with a reported in-hospital prevalence of up to 7.7% [2]. Since thirst and free access to water are the most important mechanisms that prevent hypernatremia, critically ill patients and older patients are at high risk for this disorder [4,11]. Only 2.5% patients have been found to develop moderate to severe hypernatremia in the general in-hospital population of patients. Higher prevalence has been Abstract Background: Dysnatremia is the most common elect roly te disorder in hospi tal ized pat ients ; i t encompasses hyponatremic and hypernat remic condi t ions . Dysnatremia is also a common f inding at In tensive Care Uni t admission. Abnormal serum sodium concentrat ions are known to adversely af fect physiologic funct ion and an increasing evidence suggests that dysnatremia may be associated wi th adverse outcome.