An Overview of Hypernatremia

Proper Management of a High Blood Sodium Test

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Hypernatremia is an elevated concentration of sodium ions in the blood that can happen after decreased fluid intake. It may not cause any symptoms, but it can increase the risk of other medical problems and even death. Hypernatremia is an especially big problem in hospitalized patients, where it may affect around 2% of people admitted. Even more people may have hypernatremia at some point during hospitalization. Infants and elderly people are particularly at risk.

Symptoms

People with hypernatremia may not have any symptoms, especially if the concentration of sodium has been rising gradually.

In infants, hypernatremia might cause symptoms such as the following:

  • Increased rate of breathing
  • Muscle weakness
  • Lethargy
  • Insomnia
  • High-pitched cry
  • Coma 

An adult with hypernatremia might have somewhat different types of symptoms, like:

  • Increased thirst
  • Nausea and vomiting
  • Restlessness
  • Muscle weakness

Symptoms of hypernatremia are more likely to be severe if the level of sodium gets exceptionally high. Symptoms are also more likely if a person has developed hypernatremia suddenly instead of developing it gradually. (This latter is more common.)

Overall, people hospitalized who have hypernatremia tend to have a higher risk of medical complications and death compared to people who don’t have hypernatremia. One study of people hospitalized in the intensive care unit found a 33% mortality rate in people who had hypernatremia at hospital admission. In contrast, the rate was 15% in those who did not.

One possible complication of hypernatremia is intracranial bleeding (bleeding inside the brain). This can happen when the hypernatremia causes brain cells to shrink in size, increasing the chance of a blood vessel breaking in the brain. This is the most serious potential complication of hypernatremia.

Causes

Importance of Sodium Concentration

Hypernatremia is defined as an increased concentration of sodium ions in the blood. Sodium ions are electrolytes, small charged particles that play a number of important roles. These sodium ions are the same type of substance found as a component of table salt (sodium chloride). Sodium ions are the most common ion found outside cells and in the bloodstream.

Having the right concentration of sodium in the blood is very important for your body. This is critical for the way your body regulates how much water is inside cells. This helps make sure that they don’t swell excessively or contract too much. It is also important for keeping your blood pressure in the right range. The sodium in your blood also plays complex roles in supporting nerve cell function and in the transport of materials into and out of cells.

Because the concentration of sodium ions in the blood is so important, your body has ways to regulate this. One way is through antidiuretic hormone (ADH), which is released by the pituitary gland in the brain. It triggers the kidneys to release less water through the urine if you are getting dehydrated. It also increases one’s sense of thirst. This helps increase water in the body, which lowers the concentration of sodium in the blood.

However, even with this adaptability, sometimes the body fails to keep the sodium concentration within a normal range. When the concentration gets too high, that’s called hypernatremia. (Hyponatremia is another problem, in which the concentration gets too low. It has different causes and leads to other potential problems.)

Specific Causes of Hypernatremia

Hypernatremia is usually caused by a loss of water in the body. That might happen because of decreased intake of water or increased loss of water. More rarely, hypernatremia can happen when a person takes in excess amounts of sodium. (When this happens, it’s often in hospitalized patients who have been given IV fluids containing too much sodium.)

Inadequate intake of water has a number of different possible causes. Water simply might not be available. Or, for a variety of reasons, a person might not be drinking as much as they should. This might happen, for example, from some of the following:

  • Dementia
  • Severe depression or other psychiatric disorder
  • Patient sedation
  • Brain disorder that affects a person’s thirst and production of ADH (e.g., Parkinson’s disease, brain tumor)

Increased loss of water by the body can also have different causes, as extra water leaves through the gastrointestinal tract, the urine, or through other avenues. Some of these include:

  • Diarrhea
  • Vomiting
  • Fever
  • Excess sweating
  • Severe burns
  • Very rapid breathing
  • Diuretic medications
  • Various kinds of genetic and acquired kidney disease
  • Elevated levels of blood glucose (such as from untreated type 2 diabetes)
  • Hyperaldosteronism
  • Diabetes insipidus

Certain medications may also cause hypernatremia as a side effect. These include lithium, phenytoin, and amphotericin.

Populations at Risk

Infants and the elderly are most susceptible to hypernatremia. Obviously, infants are not able to control their own intake of fluids. They also have a high surface area compared to their weight, which makes them susceptible to increased water loss. They may easily become dehydrated from a stomach bug or if they are having trouble with breastfeeding.

Elderly people tend to have a less sensitive thirst response, reduced ability to form concentrated urine, and decreased water stores. They may also have additional medical conditions that increase risk, or they may take medications with potential side effects of hypernatremia.

Hypernatremia and Diet

Hypernatremia is NOT caused by eating a lot of salty foods. The salt you get through your diet should not be enough to cause hypernatremia, even if you eat a lot of foods heavy in salt. But eating too much salt might lead to other health problems, like high blood pressure.

Diagnosis

Blood Levels

A blood sodium test is needed to diagnose hypernatremia. Using this test, hypernatremia is usually defined as having a serum sodium greater than 145 (in mEq per L). Severe symptoms are most likely to happen if a person’s sodium is even higher, say 160 or more. The blood sodium test is usually performed along with other basic tests for electrolytes and other important blood products.

Medical History, Exam, and Other Lab Tests

The clinician must also diagnose the underlying cause of the elevated sodium. That’s important, because different underlying causes have some different treatments.

To do this, the medical history is critically important. The clinician needs to know about symptoms, when they started, and other medical problems. A medical exam is also a key component of diagnosis. For example, a doctor might notice signs of dehydration like dry mouth or flaccid-appearing skin.

Often, a clinician can make a diagnosis of the underlying cause with the help of the medical history and clinical exam alone. For example, if it’s known that a person hasn’t been drinking enough water, the cause of hypernatremia is usually clear. But some of the time, additional tests may be needed. These may differ depending on the surrounding circumstances. These might include:

  • Blood tests for electrolytes and other components of a basic metabolic panel
  • Urine tests for volume and concentration

Depending on the context and available clues, other tests might be needed. For example, your clinician might see how well your body makes concentrated urine in response to desmopressin (which acts like ADH). This can help your clinician diagnosis different kinds of diabetes insipidus, if present. Or some people might need a CT scan of their head, to make sure a brain bleed isn’t present.

Treatment

Treatment of hypernatremia depends somewhat on the underlying cause. It’s important to address whatever caused the elevated sodium to begin with. For example, someone with central diabetes insipidus might need to be treated with desmopressin. It’s also important to evaluate whether a medication might be the cause of the hypernatremia.

It’s critical to replenish any lost fluids. Sometimes this can just be done orally. Other times, a person will need to receive intravenous fluids to increase the amount of water in their blood (and therefore decrease the concentration of sodium).

It’s important that your medical team correct this hypernatremia gradually. Overly rapid treatment of hypernatremia can cause brain swelling in some cases. Seizures are another possible risk. So it’s critical that your health care team give your body a chance to adapt. In people who had had hypernatremia that developed over a long period of time, treatment with fluids needs to be more gradual than in people who developed it more rapidly.

You’ll also need repeated monitoring of sodium levels in the blood, to make sure the levels go back to normal with treatment.

A Word From Verywell

If you are advocating for someone with hypernatremia, other health problems are likely to be present as well. But hypernatremia is a medical situation that needs to be taken seriously in and of itself. Though it may or may not be causing symptoms, it needs to be addressed. Don’t hesitate to ask your health care team about how exactly they plan to tackle this problem. 

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