(hī‵pĕr-nā-trē'mē-ă )

[hyper- + natremia]

An elevated concentration of sodium in the bloodstream. Hypernatremia is present when the sodium concentration exceeds about 145 mmol/L. It is usually caused by dehydration (e.g., in patients who cannot drink enough water) and not an excess of salt intake. Rarely, it may develop as a result of diabetes insipidus (a condition in which urine is not appropriately concentrated), or after intravenous infusions with high sodium chloride, sodium bicarbonate, or mannitol concentrations. Symptoms of hypernatremia include thirst, orthostatic dizziness, altered mental status, and neuromuscular dysfunction.