History & Epidemiology
Hypernatremia is a condition caused by an abnormally high level of sodium in the blood, with a serum sodium concentration of greater than 145 mEq/L.1 Hypernatremia has several potential causes including dehydration, excessive sweating, and use of certain medications.1 Infants, older adults, and those receiving inpatient hospital care are at greatest risk for hypernatremia.1
Concentrated Urine for Equilibrium
To prevent hypernatremia, the body typically maintains equilibrium of fluid and sodium balance by concentrating the urine.1 The primary mechanisms for urine concentration occur through vasopressin, also known as antidiuretic hormone (ADH), as well as through the thirst response.1
Hypernatremia occurs when there is not enough water in the blood or when there is too much sodium in the blood.1 As a result, there are two types of hypernatremia.
Hypovolemic hypernatremia occurs with both water loss and lost sodium in the blood, but more water is lost than sodium loss, comparatively.1 For example, causes of hypovolemic hyponatremia can include acute events such as vomiting, burns, or excessive sweating.1
Water loss can also occur due to several chronic conditions. One important chronic etiology of hypovolemic hypernatremia is diabetes insipidus (DI).1,2 The two types of DI are central diabetes insipidus and nephrogenic diabetes insipidus.1,2
Hypervolemic hypernatremia is less common. Causes of hypervolemic hypernatremia include improper infant formula mixing, excess sodium bicarbonate ingestion, and saltwater drowning, among others.1
Patients receiving inpatient hospital care are also at risk of iatrogenic hypervolemic hypernatremia due to the administration of intravenous (IV) fluids.1,3
Hypernatremia Diagnosis & Presentation
Dehydration, including an increased thirst response, is most common when the concentration of serum sodium is less than 160 mEq/L.1 When serum sodium concentration is greater than 160 mEq/L, symptoms such as irritability and agitation may occur, typically seen in infants and children.1 These symptoms may progress to more serious ones such as lethargy, somnolence, and coma.1
In hypovolemic hypernatremia, orthostatic hypotension and tachycardia may also occur.1 Patient with DI tend to have polyuria and polydipsia.1
The etiology and duration of hypernatremia are primarily established through the medical history and physical exam.1,3 Helpful laboratory studies to differentiate etiologies of hypernatremia include plasma volume, plasma osmolality, urine volume, concentrating ability, and osmolality.1
For patients with suspected DI, the water deprivation test is the preferred diagnostic test for hypernatremia.2 This test involves inducing hypernatremia via water deprivation followed by administration of a vasopressin challenge.2
Differential Diagnosis of Hypernatremia
The differential diagnosis of hypernatremia is broad. Distinguishing between central and nephrogenic diabetes insipidus is essential if DI is suspected as the potential cause of hypernatremia.1 Administering desmopressin allows for differentiation because a positive response to it only occurs in central DI.4
Acute and chronic etiologies of hypernatremia, such as diarrhea, cirrhosis, hypocalcemia, hyponatremia, thirst defect, and type 1 diabetes mellitus, should also be considered.1
(Nonpharmacotherapy and Pharmacotherapy)
The primary goal of acute hypernatremia management is to correct the concentration of serum sodium and intravascular volume.1 Treatment should also address the underlying cause of the hypernatremia.1
The focus of acute management is administration of fluids to correct the hypernatremia.1,3 Administering fluids orally or through a feeding tube is preferred to administering IV fluids, when possible.1,3
One formula used for correcting water deficit is 4 ml x bodyweight x (desired change in serum sodium mEq/L).1 In order to avoid adverse effects, such as cerebral edema and seizures, serum sodium correction should be done slowly, decreasing the serum sodium level by no more than 12 mEq in 24 hours.1
Management of the underlying causes of hypernatremia depends on etiology.2 The medication desmopressin is used for the management of central diabetes insipidus, while thiazide diuretics may be used to treat nephrogenic DI.2 Thiazide diuretics work to decrease urine volume and increase urine osmolality.3 A low-salt diet eliminating too much sodium intake and balancing fluid intake and water intake may also be prescribed for hypernatremia.2
Monitoring Side Effects, Adverse Events, Drug-Drug Interactions
Due to the potential for adverse effects from fluid administration, such as cerebral edema and seizures, serial serum sodium measurements should be taken every 2 to 4 hours during the acute management phase when fluids are administered to manage hypernatremia.1 In addition to monitoring the rate of correction of serum sodium levels, urine output and ongoing losses should also be monitored when managing hypernatremia.1
Desmopressin is a synthetic analog of vasopressin and works on vasopressin receptors.4 In the outpatient setting, desmopressin is typically administered intranasally, but it is also available as an IV formulation.4 The dosage is based on patient weight.4 The main adverse effect of desmopressin is hyponatremia, which occurs due to increased urine concentration.4 Other adverse effects include headache, tachycardia, and facial flushing.4
Contraindications to the use of desmopressin include patients with hyponatremia, type 3 von Willebrand disease, thrombocytopenic purpura, and known hypersensitivity to desmopressin acetate. 4 As this medication acts on the nephron in the kidney, desmopressin should also be used with caution in patients with altered renal function.4
Thiazide diuretics act on the distal convoluted tubule of the nephron to promote natriuresis and diuresis.5 Adverse effects of thiazide diuretics include electrolyte imbalances, such as hypokalemia, hyponatremia, metabolic alkalosis, and hypercalcemia. Other adverse effects include hyperglycemia, hyperuricemia, hyperlipidemia, and sulfonamide allergy.5 Thiazide diuretics use is contraindicated in patients with sulfonamide allergies because they are sulfa-containing medications.5
Because there is also risk of acute pancreatitis in hypernatremia, patients must be monitored for these symptoms.5 If symptoms of pancreatitis occur alongside hypernatremia, medication use must be discontinued immediately and should not be resumed.5
1. Sonani B, Naganathan S, Al-Dhahir M. Hypernatremia. In: StatPearls. NCBI Bookshelf version. StatPearls Publishing: 2022. Accessed July 27, 2022.
2. Qian Q. Hypernatremia. Clin J Am Soc Nephrol. 2019;14(3):432-434. doi:10.2215/CJN.12141018
3. Muhsin S, Mount DB. Diagnosis and treatment of hypernatremia. Best Pract Res Clin Endocrinol Metab. 2016;30(2):189-203. doi:10.1016/j.beem.2016.02.014
4. McCarty T, Shah A. Desmopressin. In: StatPearls. NCBI Bookshelf version. StatPearls Publishing: 2022. Accessed July 27, 2022.
5. Akbari P, Khorasani-Zadeh A. Thiazide Diuretics. In: StatPearls. NCBI Bookshelf version. StatPearls Publishing: 2022. Accessed July 27, 2022.
Anna Courant is a nurse practitioner and writer.