Sodium is an important electrolyte in the body that is responsible for regulating body fluid, maintaining blood pressure, and aiding proper nerve and muscle function. Normal blood plasma contains 136 to 145 mEq/L of sodium, according to MayoClinic.com. When sodium in blood plasma falls below 135 mEq/L, it is considered a low serum sodium level, or hyponatremia.
Types
Three major types of hyponatremia have been identified: hypervolemic, euvolemic and hypovolemic. Hypervolemic hyponatremia occurs when excess water in the body causes a low serum sodium level. Euvolemic hyponatremia is characterized by normal water levels, but low sodium levels. Hypovolemic hyponatremia occurs when both the water levels and serum sodium levels are low. Hyponatremia may also be classified as acute or chronic. Acute hyponatremia occurs rapidly and suddenly whereas chronic hyponatremia develops gradually over time.
Causes
Underlying medical conditions are a common cause of hyponatremia, including adrenal gland insufficiency, hypothyroidism, cirrhosis, kidney disease or heart failure. Certain lifestyle factors such as the use of diuretics, excess water consumption and a low-sodium diet can also lead to hyponatremia. Intense exercise, such as marathons and triathlons, can lead to heavy sweating and ultimately cause hyponatremia if fluid and electrolytes are not replaced. Those who have an acute illness, such as food poisoning, that causes severe vomiting or diarrhea can also develop low serum sodium levels.
Symptoms
Depending on how low serum sodium levels are, symptoms of hyponatremia can range from mild to severe. Some mild symptoms include nausea, vomiting, headache, weakness, fatigue, loss of appetite and irritability. As the sodium levels drop, symptoms become more severe, including muscle cramps, seizures and loss of consciousness, according to MayoClinic.com. Mental changes are a common symptom of low serum sodium levels as well and may appear as hallucinations, confusion or coma.
Treatment
Medline Plus notes that treatment depends on the underlying cause and specific type of hyponatremia. Chronic hyponatremia can usually be successfully treated with restriction of fluids. Immediate treatment for acute hyponatremia may include intravenous fluids and electrolytes, restriction of water and medications for management of individual symptoms.
Complications
Hyponatremia that develops slowly over time does not usually cause any serious complications. The condition is usually moderate and can be treated easily. Acute hyponatremia can result in swelling of the brain, which can lead to coma and death.
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