Hyponatremia treatment should be based on the mechanism governing the impaired urine dilution and address the underlying cause of the condition.
Hyponatremia is the most common electrolyte disorder seen in clinical practice, affecting up to 30% of hospitalized patients. It has been estimated that up to 15% of patients in the US with hyponatremia also have cerebral symptoms (including nausea and vomiting, decreased consciousness, confusion, seizures, and coma), mostly caused by cerebral edema.
Because hyponatremia is associated with high mortality, prompt diagnosis and treatment is essential. However, according to the authors of “Initial Approach to the Hyponatremic Patient,” published in the February 2011 issue of Acta Anaesthesiologica Scandiavica, there is considerable controversy over which treatment approach is best. They identified a number of factors that make the diagnosis and treatment of hyponatremia problematic (under-diagnosis, complications from overcorrection and osmotic demyelination, challenges in the clinical application of traditional classifications, etc). Specific treatment challenges include:
In terms of identification and diagnosis, the authors wrote that hyponatremia is characterized by “an impaired ability to excrete properly diluted urine and downward resetting of the osmotic threshold for thirst” caused by insufficient suppression of antidiuretic hormone (ADH) secretion. The authors noted that this “defect in urine dilution” can be identified with an abnormal water load test and that clinicians can identify hyponatremia types by considering the mechanisms preventing urine dilution. They identified two groups: one that includes “syndromes in which ADH is inappropriately elevated [syndrome of inappropriate ADH secretion (SIADH)],” and a second group that includes “conditions wherein ADH is elevated as a homeostatic response to other diseases.” In this latter group, ADH secretion is stimulated by “a reduced effective arterial blood volume (EABV) sensed by the arterial baroreceptors.”
Accordingly, the authors of this study sought to present “a practical approach to this intriguing condition that rests on an understanding of the changes in plasma [Na ] and the effects of hyponatremia on the brain.” Data used in this study was collected during a literature search using MEDLINE, Embase, and The Cochrane Library.
The authors stated several pertinent observations, recommendations, and conclusions in this paper, including:
The authors summarized the results of their study by noting that the” emerging consensus regarding the initial treatment of hyponatremia” supports the use of bolus therapy with 2 ml/kg 3% saline. They urged clinicians to avoid overcorrection and OD and focus treatment decisions on addressing the underlying cause of hyponatremia. They noted that this can be “a challenging task and traditional classifications based on hydration are difficult to use in the clinic. Therefore, an approach based on the mechanism governing the impaired urine dilution has been proposed.”