ABSTRACT
Hyponatremia, defined as a blood sodium concentration of <135 mmol/L is the most common electrolyte abnormality observed in the intensive care unit (ICU). Hypernatremia may be present on admission or develop during the ICU stay. When hypernatremia develops, there is movement of water out of cells into the extracellular fluid and a decrease in cell size results. Treatment for hypernatremia was investigated in a retrospective study that explored a large database of ICU patients at Beth Israel Deaconess Medical Center, the Medical Information Mart for Intensive Care-III. Care of patients with hypernatremia should include calculation of the water deficit and consideration of ongoing losses. Hypernatremia may be caused by water loss or sodium gain. Water loss can develop from gastrointestinal losses from emesis, diarrhea, or surgical drainage of gastrointestinal fluids. Osmotic demyelination has also been reported in patients who have developed hypernatremia abruptly in the setting of severe hyperglycemia or diabetes insipidus.
