Acute hospital-induced hyponatremia in children: A physiologic approach

Physicians giving children fluid therapy today seldom encounter overt dehydration or signs of shock that call for rapid and aggressive extracellular fluid (ECF) expansion. Physicians in the era when severe diarrheal dehydration was common first restored ECF with isotonic saline,^a then planned maintenance and replacement therapies, using hypotonic saline. Today, physicians plan fluid therapy mostly for children with pneumonia, meningitis, other acute disorders, or for children scheduled for surgery. These children are seldom overtly dehydrated or in shock. Common practice in this setting is to initiate fluid therapy with hypotonic saline as maintenance therapy. However, hyponatremia has been a worrisome complication with this practice. In extreme cases, convulsions, brain injury, or death have resulted.⁴ Two recent articles have recommended giving maintenance therapy as isotonic saline to avoid this risk. While authors of these articles have done a service in calling attention to the problem of hyponatremia, we believe their remedy has risks of its own. Our analysis of the cases we reviewed suggests a more physiologic approach, using tested principles of fluid therapy.

ADH, Antidiuretic hormone, ECF, Extracellular fluid, SIADH, Syndrome inappropriate secretion of antidiuretic hormone

• a The term “normal saline,” although widely used, is not permitted in labeling by FDA because it is not a chemically defined normal solution. Isotonic saline is 0.9% saline (154 mEq/L Na). Hypotonic saline solutions vary between 0.45% and 0.18% saline (77 and 30 mEq/L Na) and deliver between 1/2 and 4/5 of their volume as free water.