The Challenge of Hyponatremia

Abstract

Treatment of hypotonic hyponatremia often challenges clinicians on many counts. Despite similar serum sodium concentrations, clinical manifestations can range from mild to life threatening. Some patients require active management, whereas others recover without intervention. Therapeutic measures frequently yield safe correction, yet the same measures can result in osmotic demyelination. To address this challenge, we present a practical approach to managing hyponatremia that centers on two elements: a diagnostic evaluation directed at the pathogenesis and putative causes of hyponatremia, the case-specific clinical and laboratory features, and the associated clinical risk; and a management plan tailored to the diagnostic findings that incorporates quantitative projections of fluid therapy and fluid losses on the patient's serum sodium, balances potential benefits and risks, and emphasizes vigilant monitoring. These principles should enable the clinician to formulate a management plan that addresses expeditiously three critical questions: Which of the determinants of the serum sodium are deranged and what is the underlying culprit? How urgent is the need for intervention? What specific therapy should be instituted and which are the associated pitfalls?

Treatment of Hyponatremia: What the Clinician Needs to Know

“…Hyponatremia (serum sodium <135mEq/L) is the most common electrolyte abnormality, is due to different pathophysiologic mechanisms, is associated with increased morbidity and mortality and its appropriate treatment is still a therapeutic challenge [1,2] . Even though clinical practice guidelines on the treatment of hyponatremia…”

“…In this setting potassium anions should be taken into account in the calculation of the tonicity of the infused solutions. Interestingly, the infusate formula proposed by the Adrogue-Madias and verified by Liamis et al can reliably project the effect of gaining 1L of any infusate on the patient's serum sodium (ΔΝα + s) and thus can be used to calculate the rate of the administered 0.9% NaCl solution [2,11,12] . …”

“…Consequently, the initial approach to the hyponatremic patient includes the determination of Posm (by an osmometer if it is available) as well as the exclusion of pseudohyponatremia (due to severe hypercholesterolemia, hypertriglyceridemia, and hyperproteinemia) or hypertonic hyponatremia [due to the presence of osmotic active agents, such as glucose (hyperglycemia) or the administration of mannitol or glycine] [2,7,8] . It is worth mentioning that in hyperglycemic individuals the corrected serum sodium levels should be calculated by increasing the measured serum sodium levels by 2.4 mEq/L for each 100mg/dl of glucose above normal [4,8] .…”

“…However, increased urine sodium levels (>30 mEq/L) can also be encountered in patients with extracellular volume contraction with renal or adrenal insufficiency, severe metabolic alkalosis, osmotic diuresis, as well as in those on thiazides [2,8] .…”

“…Thus, prompt recognition of an increased diuresis (>100 mL/h) and repeated determinations of serum sodium levels are mandatory to avoid hypercorrection of serum sodium levels leading to osmotic demyelination. Moreover, conditions such as hypokalemia, chronic alcoholism, malnutrition, underlying liver disease or serum sodium <105 mEq/L associated with high risk of this syndrome should be readily recognized [2,8] .…”