Resumen de Prevalencia de hiponatremia en pacientes con nutrición parenteral. Morbimortalidad asociada
Hyponatremia is the most common electrolyte disorder in clinical practice. Patients with hyponatremia present high morbimortality rates. The prevalence of hyponatremia among hospitalized patients has been found to vary from 30 to 42%, when defined as a serum sodium level (SNa) below 136 mmol/L, and to be 19.7% when defined as a SNa below 135 mmol/L. In these patients, hyponatremia is most often present at admittance, and is mild (SNa between 130 and 134 mmol/L). However, when hyponatremia is hospital-acquired, it is more often moderate or severe. Several studies have found a high mortality rate in hospitalized hyponatremic patients as compared with those presenting normal SNa. Such is the case in patients with severe hyponatremia (SNa < 120-125 mmol/L) as well as in mild forms. Minor descents in SNa of the order of 4 to 5 mmol/L are already accompanied by an increased mortality rate. In fact, some authors have detected a minimum mortality rate in patients with SNa between 138–142 mmol/L, postulating these levels as representing strict eunatremia. Hyponatremic patients also have longer hospital lengths-of-stay, as well as a higher readmissions rate. Hyponatremia is a consequence of an alteration in water metabolism, most often due to a reduced renal capacity to eliminate free water (antidiuresis), secondary to a non-osmotic increase in the secretion of Arginine Vasopressin (AVP), the Antidiuretic Hormone (ADH) of humans. This increase can be induced by physiologic stimuli (post-surgical stress, pain, nausea...) or by nonphysiologic, inappropriate AVP secretion (the Syndrome of Inappropriate Antidiuretic Hormone Secretion or SIADH). The combination of persistent AVP secretion together with increased oral or parenteral fluid intake results in plasmatic hypoosmolality, and induction or exacerbation of hyponatremia...
