Endocrinology & Metabolic Syndrome
Open Access

Hypernatremia

Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the blood. Early symptoms may include a strong feeling of thirst, weakness, nausea, and loss of appetite.Severe symptoms include confusion, muscle twitching, and bleeding in or around the brain.Normal serum sodium levels are 135–145 mmol/L (135–145 mEq/L). Hypernatremia is generally defined as a serum sodium level of more than 145 mmol/L.Severe symptoms typically only occur when levels are above 160 mmol/L.

Hypernatremia is typically classified by a person's fluid status into low volume, normal volume, and high volume. Low volume hypernatremia can occur from sweating, vomiting, diarrhea, diuretic medication, or kidney disease. Normal volume hypernatremia can be due to fever, inappropriately decreased thirst, prolonged increased breath rate, diabetes insipidus, and from lithium among other causes. High volume hypernatremia can be due to hyperaldosteronism, excessive administration of intravenous 3% normal saline or sodium bicarbonate, or rarely from eating too much salt.Low blood protein levels can result in a falsely high sodium measurement. The cause can usually be determined by the history of events.Testing the urine can help if the cause is unclear.The underlying mechanism typically involves too little free water in the body.

If the onset of hypernatremia was over a few hours, then it can be corrected relatively quickly using intravenous normal saline and 5% dextrose in water. Otherwise, correction should occur slowly with, for those unable to drink water, half-normal saline.Hypernatremia due to diabetes insipidus as a result of a brain disorder, may be treated with the medication desmopressin. If the diabetes insipidus is due to kidney problems the medication causing the problem may need to be stopped or the underlying electrolyte disturbance corrected.Hypernatremia affects 0.3–1% of people in hospital.It most often occurs in babies, those with impaired mental status, and the elderly.Hypernatremia is associated with an increased risk of death but it is unclear if it is the cause.