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Hyponatremia: Symptoms, Causes, and Treatments

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Hyponatremia is usually discovered on laboratory tests as a lower than normal sodium level in the blood. It will appear as sodium or Na+ in your lab results. Actually, the main problem in the vast number of situations is too much water that dilutes the Na+ value rather than too much sodium. As a result, water moves into body cells, causing them to swell. This swelling causes the major problem, which is a change in mental status that can progress to seizures or coma.

Hyponatremia can result from multiple diseases that often are affecting the lungs, liver or brain, heart problems like congestive heart failure, or medications. Most people recover fully with their doctor’s help.


Who is most at risk for hyponatremia?

Anyone can develop hyponatremia. Hyponatremia is more likely in people living with certain diseases, like kidney failure, congestive heart failure, and diseases affecting the lungs, liver or brain. It often occurs with pain after surgery. Also, people taking medications like diuretics and some antidepressants are more at risk for this condition.

How common is hyponatremia?

Hyponatremia is very common. Hyponatremia is the most common chemical abnormality seen among patients in the hospital. Rates of hyponatremia are higher among people admitted to inpatient hospital care units or with the medical conditions mentioned above.

What causes hyponatremia?

In general, too much water in your body is usually the main problem and this dilutes the sodium levels. Much less frequently, hyponatremia is due to significant sodium loss from your body.

Too much water in your body causes your blood to become “watered down.” A good example is people who run in long races or run on hot days. They lose both salt and water in their sweat and often replace these losses with mostly water. This combination can be deadly because it dilutes the remaining sodium in the body.

It’s also possible to lose too much sodium from your body. Medications, like diuretics, can cause your kidneys to increase the amount of sodium excreted in urine. Medical problems like diarrhea may cause excessive sodium loss if left untreated. Chronic or binge alcohol consumption can cause people to lose too much sodium through increased urination and vomiting. You can have hyponatremia without feeling dehydrated or volume depleted. This is most often the case in hospitalized patients.

What are the symptoms of hyponatremia?

Hyponatremia causes neurologic symptoms ranging from confusion to seizures to coma. The severity of the symptoms depends on how low the sodium levels are in the bloodstream and how quickly they fall. In many cases, blood sodium levels fall gradually, producing only mild symptoms as the body has time to make adjustments. Symptoms are more serious when blood sodium levels fall quickly.

Other symptoms of moderate to severe hyponatremia include:

  • Muscle cramps or weakness
  • Nausea and vomiting
  • Lethargy, or low energy
  • Headache and confusion
  • Mental status changes
  • Seizures

How is hyponatremia diagnosed?

The only way your doctor can know that hyponatremia is present is with blood tests that measure the amount of sodium (Na+) in the bloodstream. Your doctor will also perform a physical examination to detect the severity and cause(s) of hyponatremia.

How is hyponatremia treated?

Treatment for hyponatremia depends on the underlying cause and the severity of your symptoms. If you have mild symptoms, your doctor makes small adjustments to your therapy to correct the problem. This usually involves restricting water intake, adjusting medications and removing or treating the causes. Therapy may be short-term or long-term. For the short-term, we may restrict water intake, adjust or stop medications, and treat any underlying problems. For the long-term, we may continue the short-term treatments and add salt to your diet or try some newer medications.

People with moderate to severe hyponatremia require thorough medical evaluation and treatment, usually in the hospital. For the sickest patients, we may replace sodium intravenously (straight into a vein) and really limit water consumption. Certain newer medications, like tolvaptan (Samsca®), may be used to correct blood sodium levels.

Treatment to correct any underlying medical problems – like congestive heart failure (when poor heart function causes fluid to build up in the body) – is also used to improve hyponatremia.

What complications are associated with hyponatremia?

In many cases, hyponatremia causes extra water to move out of the bloodstream and into body cells, including brain cells. Severe hyponatremia causes this to occur quickly, resulting in swollen brain tissue. If left untreated, complications can include:

  • Mental status changes
  • Seizures
  • Coma
  • Death

Can hyponatremia be prevented?

If you have certain underlying medical conditions, particularly involving the kidneys, heart, lung, liver or brain, hyponatremia is more likely. You can lower your risk for hyponatremia by following your treatment plan and restricting your water intake to levels recommended by your doctor. Also, notify your doctor of any new symptoms immediately. Monitoring must include blood tests.

What are the outcomes after treatment for hyponatremia?

With treatment, many people recover fully from hyponatremia. Even long-term hyponatremia can be managed and problems prevented.

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