Hypernatremia

An abnormally elevated serum sodium concentration (>145 mmol/L) usually reflecting a deficit of free water relative to total body sodium and predisposing to cellular dehydration, particularly of the central nervous system. Possible causes are inadequate water intake, excessive fluid loss (fever, tachypnea, diarrhea, vomitin, hyperhidrosis, burns), diabetes insipidus, osmotic diuresis, medications (diuretics, lithium), and sodium overload (salty diet, intravenous NaCL).