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What Is Hypernatremia?

Mariya Rizwan, PharmD

Hypernatremia occurs when the sodium levels in the body rise above the normal value. Sodium is an electrolyte, and if it gets too high or low, it can result in life-threatening consequences. Therefore, maintaining optimal sodium levels is essential. When the serum concentration of sodium increases to more than 145 milliequivalents per liter (mEq/L), the condition is known as hypernatremia. The normal serum sodium level is 136 to 145 mEq/L.

Sodium is the human body's most abundant cation (positively charged ion). A 70-kilogram (kg) man has around 4200 mEq of sodium. About 70% of sodium in the body is exchangeable, either dissolved in the extracellular fluid (ECF) compartment or remaining in communication with it. The remaining 30% is silent sodium, which cannot be exchanged.

Sodium has various functions in the human body, such as maintaining the osmolarity of the ECF, maintaining the volume of the ECF and water distribution, and affecting the concentration, excretion, and absorption of other electrolytes, most importantly, potassium and chloride ions. Sodium combines with other ions to maintain acid-base balance and is essential for impulse transmission of muscle fibers and nerves.

Hypernatremia is a quite rare imbalance that occurs in less than 1% of all hospital admissions and is unusual in conscious patients with intact thirst response. However, when it happens, the mortality rate can be as high as 50%.

Hypernatremia often occurs when the levels of sodium are in excess in relation to water content in the ECF compartment, hence resulting in hyperosmolarity of the ECF, which in turn causes a shift in water from the cells to the ECF, eventually resulting in dehydration. Hypernatremia can lead to three different manifestations based on the ratio of total body water to total body sodium. They include:

  • Hypovolemic hypernatremia
  • Hypervolemic hypernatremia
  • Euvolemic hypernatremia

The most common type is hypovolemic hypernatremia, in which total body water decreases more than the loss of sodium ions. It can occur because of non-renal causes such as fever, diarrhea, vomiting, heat exposure, severe burns, profuse diaphoresis, and insensible loss from mechanical ventilation. Renal causes for hypovolemic hypernatremia include diuresis, increased urea production because of high protein diet consumption, severe hyperglycemia, and intravenous administration of mannitol.

Hypervolemic hypernatremia is the least common type in which the total body weight remains normal, with increased sodium levels. It can occur because of the over-administration of saline solutions, especially in patients with diabetes, ketoacidosis, and osmotic diuresis. Moreover, it can also occur because of the over-administration of salt solutions and salt over-ingestion.

In euvolemic hypernatremia, the total body weight is decreased relative to the normal total body sodium. It can occur because of diabetes insipidus, debilitated patients, and hypodipsia in infants and older adults.


If you suspect the patient has hypernatremia, take a detailed medication and disease history. Make sure to inquire about how much salt the patient consumes daily and ask about their daily fluid consumption. Often, patients with hypernatremia are informed about less fluid and possibly more salt consumption. An early sign of hypernatremia is polyuria, moving to oliguria. Therefore, the patient should be asked about their daily urine output and whether it appears concentrated.

Ask the patient about other symptoms, such as diarrhea, fever, and vomiting, that can lead to dehydration. Furthermore, if the patient has severe hypernatremia, they may be confused. Ask their caregivers if the patient is disoriented, agitated, or lethargic. These symptoms, accompanied by a seizure, indicate severe hypernatremia.

On physical examination, the patient may be asymptomatic or have non-specific symptoms such as nausea, agitation, vomiting, and other signs of dehydration. Assess the patients vital signs and inspect them for fever, hypotension, tachycardia, and orthostatic hypotension, as these are the signs of hypernatremia. Check the patients skin and mucus membrane for signs of dehydration. Severe hypernatremia causes poor skin turgor, flushed skin color, a rough and dry tongue, and mucous membranes. Even more severe hypernatremia can cause muscle twitching, tremors, seizures, hyperreflexia, and rigid paralysis.

Assess if the patient can take fluid by mouth. If the patient is lethargic, that may lead to poor fluid intake. Hypernatremia also causes neurological symptoms; therefore, the patients communication status and levels of orientation should be assessed. For disorientated and debilitated patients, assess their safety needs. Neurological symptoms may be upsetting for the patient and anxiety-provoking for the family. You must counsel them and inform them why it is happening.

Nursing Implementations

When hypernatremia occurs, the goal is to decrease the total body sodium and replenish fluid loss. Encourage the patients to drink plenty of fluids, especially plain water. However, if the patient can not tolerate fluids, administer a hypotonic electrolyte solution through an intravenous route that contains 0.2% or 0.45% sodium chloride or order a salt-free solution. Sometimes, these two types of solutions are used alternatively to prevent hypernatremia.

If the physician orders 5% dextrose in water, monitor the urine output because it encourages diuresis, which can, in turn, aggravate the preexisting hypernatremia. Measure the patients body weight daily and maintain a record of output and input records.

Check the patients serum sodium levels daily to determine if the fluid administration is effective. Administer the prescribed water replacement slowly to reduce the serum sodium levels to no more than 2 mEq/L per hour. If hypernatremia is corrected too quickly with a sudden change in serum sodium level, the ECF shifts into the cells, leading to cerebral edema and neurological problems. While correcting hypernatremia, monitor the patient closely for any signs of cerebral edema, such as headache, lethargy, nausea, vomiting, widening pulse pressure, and decreased heart rate. Diuretic therapy is sometimes indicated in hypernatremia to increase sodium excretion and decrease sodium intake through the mouth. Other than IV therapy, no other pharmacological management is usually required.

Ask the patient with hypernatremia to drink plenty of fluids, especially water. Moreover, they should be asked to avoid consuming caffeinated fluids and alcohol because they increase serum sodium levels by increasing water diuresis. The water leaves the patients body, leaving the sodium behind, hence leading to hypernatremia.

Notify the physician promptly if you notice any changes in the patients mental status or symptoms, such as agitation, confusion, and disorientation. Initiate seizure precautions if the patient is at risk of seizures.

Give oral care to the patient with hypernatremia every two hours with lemon glycerin swabs or mouthwashes, as their mucus membrane may become dry, causing discomfort. Also, ask the patient to change positions frequently, as their skin is dry, which can become bothersome. Check if the patient can ambulate safely. Otherwise, provide them with assistance. Moreover, if the patient is disoriented, maintain the bed in the lowest position and take safety measures to prevent falling from the bed.

The Bottom Line

Hypernatremia is a serious condition in which the serum sodium levels exceed the normal limit, which can lead to life-threatening consequences such as cerebral edema and hemorrhage. If your patient is diagnosed with hypernatremia, correct it slowly with the help of fluid therapy. Make sure to rule out the underlying cause of hypernatremia to prevent its occurrence in the future.

Tell your patient to visit the emergency room promptly if they reencounter any symptoms of hypernatremia.

About the Author:

Mariya Rizwan is an experienced pharmacist who has been working as a medical writer for four years. Her passion lies in crafting articles on topics ranging from Pharmacology, General Medicine, Pathology to Pharmacognosy.

Mariya is an independent contributor to CEUfast's Nursing Blog Program. Please note that the views, thoughts, and opinions expressed in this blog post are solely of the independent contributor and do not necessarily represent those of CEUfast. This blog post is not medical advice. Always consult with your personal healthcare provider for any health-related questions or concerns.

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