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A preventable condition, hyponatremia is hard to pronounce and potentially lethal if not detected early.

What is it?

Hyponatremia is a fluid-electrolyte disorder that occurs when the sodium level in the blood drops below normal during a rapid intake of fluid. The danger arises when the body tries to re-establish the normal balance between fluid and sodium. This reaction disrupts the blood-brain barrier allowing a rapid influx of water into the brain, causing swelling that can progress from headache and confusion to seizure or coma, potentially resulting in death.

What causes hyponatremia?

Three events that usually occur in relation to each other are responsible for this condition:

  • Large losses of sodium in sweat,
  • Rapid, excessive drinking of fluids, and
  • Limited capacity of the kidneys to eliminate fluids consumed at a fast rate.

Excessive sweat or very salty sweat is by itself not dangerous. Yet, a large loss of sodium in combination with athletes trying to re-hydrate themselves at a fast rate can spell disaster.

The kidneys are usually able to eliminate about one quart of fluid per hour, however, this can be reduced by the specific activity/exercise that's pulling blood flow away from the kidneys and using it for muscles. Compared to resting rates, this decrease in blood flow will affect the processing of fluid for elimination by 20 to 60 percent. Although this effect helps conserve fluid as the body sweats, it increases the chance that excessive drinking can lead to hyponatremia by not removing the surplus fluid from the system.

Other potential factors can lead to this condition, but do require additional research:

  • Smaller athletes. The volume of body fluid is smaller, thus more sensitive to changes.
  • Rates of occurrence. Females appear to be at a higher risk for hyponatremia; they are 25 times more likely to die from this condition than males. However, the reason for the discrepancy in mortality rates is not fully understood. Anecdotal evidence assumes that females are more diligent drinkers; thus, they are more likely to follow, if not go beyond, recommendations of coaches and athletic trainers.
  • Recessive cystic fibrosis gene.

The signs and symptoms of hyponatremia include:

  • Bloated/swollen stomach, hands and feet
  • Headache
  • Nausea/vomiting
  • Confusion/disorientation
  • Decreased coordination
  • Seizure

Since this condition can progress very quickly, any of these situations should be treated as a medical emergency – call 911.

Exercise requires proper re-hydration for maximum performance; prevention should include selection of fluids that have electrolytes and sodium, a balanced diet, and education of the athletes. Athletes that lose weight during exercise should have a goal of regaining the lost weight, not gaining weight. In addition, having salty snacks can help both with fluid consumption and maintaining the sodium balance.

For more information about hyponatremia or other sports medicine topics, call the Aurora Sports Medicine Hotline™ at (414) 219-7776 or (800) 219-7776.