Hypernatremia

Hypernatremia
Other names	Hypernatraemia
Sodium
Specialty	Hospital medicine
Symptoms	Feeling of thirst, weakness, nausea, loss of appetite[1]
Complications	Cardiac arrest, confusion, muscle twitching, bleeding in or around the brain[1][2]
Types	Low volume, normal volume, high volume[1]
Diagnostic method	Serum sodium > 145 mmol/L[3]
Differential diagnosis	Low blood protein levels[4]
Frequency	~0.5% in hospital[2]

Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the blood.^[3] Early symptoms may include a strong feeling of thirst, weakness, nausea, and loss of appetite.^[1] Severe symptoms include confusion, muscle twitching, and bleeding in or around the brain.^[1][2] Normal serum sodium levels are 135–145 mmol/L (135–145 mEq/L).^[5] Hypernatremia is generally defined as a serum sodium level of more than 145 mmol/L.^[3] Severe symptoms typically only occur when levels are above 160 mmol/L.^[1]

Hypernatremia is typically classified by a person's fluid status into low volume, normal volume, and high volume.^[1] Low volume hypernatremia can occur from sweating, vomiting, diarrhea, diuretic medication, or kidney disease.^[1] Normal volume hypernatremia can be due to fever, extreme thirst, prolonged increased breath rate, diabetes insipidus, and from lithium among other causes.^[1] High volume hypernatremia can be due to hyperaldosteronism, excessive administration of intravenous normal saline or sodium bicarbonate, or rarely from eating too much salt.^[1][2] Low blood protein levels can result in a falsely high sodium measurement.^[4] The cause can usually be determined by the history of events.^[1] Testing the urine can help if the cause is unclear.^[1] The underlying mechanism typically involves too little free water in the body.^[6]

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.^[1] Otherwise, correction should occur slowly with, for those unable to drink water, half-normal saline.^[1] Hypernatremia due to diabetes insipidus as a result of a brain disorder, may be treated with the medication desmopressin.^[1] 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.^[1][7] Hypernatremia affects 0.3–1% of people in hospital.^[2] It most often occurs in babies, those with impaired mental status, and the elderly.^[2] Hypernatremia is associated with an increased risk of death, but it is unclear if it is the cause.^[2]