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Causes and Treatment of Hyponatremia

written by: Victoria Trix • edited by: Leigh A. Zaykoski • updated: 7/14/2009

Hyponatremia is an electrolyte abnormality where there is more water in the system than sodium. This means there is not enough sodium in the body to put off the water that is required on a daily basis. There are many causes and treatments available for Hyponatremia.

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    Hypo means less than or not enough, and natremia is a medical term for salt in the system. When salt levels in the fluids outside of the cells drops, the water in the system will then be pulled into the cells so that it can balance out the salt levels. When this happens, the cells swell because of too much water. While many cell types can handle this normally, brain cells cannot. The brain cells swell, but the rigidity of the skull means there is not enough room to accommodate the expansion. This is the cause of most symptoms of the disease.

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    Symptoms of Hyponatremia

    Reduced urination compared to intake of water is called primary polydipsia. This can be caused by the failure of kidneys or by too much of the anti-diuretic hormone ADH. A plasma sodium concentration, or the CBC will show above 120 meq per liter. Nausea and vomiting as well as being restless and no appetite are symptoms found in the normal course of the disease. Confusion and hallucinations as well as comas are often seen as symptoms.

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    Diagnosis of Hyponatremia

    The first day of acute hyponatremia is characterized by the brain losing water into the cerebrospinal fluid and the intracellular water mixes with salt and potassium. In severe cases of sudden onset, abrupt water movement into the brain (cerebral edema) can lead to death. This can sometimes happen when too much of the hypotonic fluid is given for treatment in patients that have recently had surgery. A serum sodium test as well as a serum osmolality can be done along with urine sodium to find out if this is the case, or if there is another disease present.

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    Treatments for Hyponatremia

    The first treatment should be a gradual correction of the salt concentration by using a water restricted diet, and then administering an isotonic saline solution that has more salt than saline. Faster therapies are used for those patients that have severe hyponatremia (where the plasma sodium concentration is below 110). The hypertonic solution can be given at first in this case to raise the plasma sodium concentration and must be monitored to keep lesions from forming.

    The type of treatment will be determined by looking at the risks associated. Based on the risk of the osmotic demyelination, the rate of correction, the best way of raising the plasma sodium concentration as well as an estimate as to how bad the sodium deficiency is and managing the patient’s system if correction is done too fast are all facts that are looked at when assessing the type of treatment given. IV fluids as well as oxygen and medications for seizures if present are also treatments for extreme cases.

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    Resources

    N.Y. Times article Hyponatremia last reviewed on August 14, 2007

    UpToDate.com from the article Treatment of Hyponatremia publication date unknown.

    National Library of Medicine from the article Hyponatremia last updated August 14, 2007