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February 3, 2012
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Dehydration

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Doctor to Patient

Exercise-Associated Hyponatremia: Who's at Risk?

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

Are you in danger of developing hyponatremia?We've all learned that fluid replacement is critical to replace fluids lost when exercising, but drinking pure water exclusively isn't the safest choice for those who participate in very strenuous or long-duration exercise.

When significant amounts of fluid are lost through high-intensity exercise, replacement with water alone can lead to a chemical imbalance in the body and deficiencies in electrolytes, which are nutrients critical for organ functioning. The electrolytes in our body include sodium, potassium, chloride, calcium and phosphate, but sodium is the substance of most concern when replacing fluids lost through exercising.

Hyponatremia is a condition in which the body's stores of sodium are too low, and this condition can result from drinking extreme amounts of water. Hyponatremia can lead to confusion, lethargy, agitation, seizures, and in extreme cases, even death. Early symptoms are nonspecific and subtle and may include disorientation, nausea, or muscle cramps. The symptoms of hyponatremia may also mimic those of dehydration, so athletes experiencing these symptoms may be given more water to drink, further worsening the condition.


Doctor to Patient

What is dehydration?

Water is a critical element of the body, and adequate hydration is a must to allow the body to function. Up to 75% of the body's weight is made up of water. Most of the water is found within the cells of the body (intracellular space). The rest is found in the extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).

Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in. The body is very dynamic and always changing. This is especially true with water in the body. We lose water routinely when we:

  • breathe and humidified air leaves the body (this can be seen on a cold day (the breath you see in the air is water that has been exhaled);

  • sweat to cool the body; and

  • eliminate waste by urinating or having a bowel movement.

In a normal day, a person has to drink a significant amount of water to replace this routine loss.

The formula for daily fluid requirements depends upon an individual's weight. Normally, fluid and weight are calculated using the metric system; however, below is the approximation in imperial (American) units.

Body weight Daily fluid requirements (approximate)
10 pounds 15 ounces
20 pounds 30 ounces
30 pounds 40 ounces
40 pounds 45 ounces
50 pounds 50 ounces
75 pounds 55 ounces
100 pounds 50 ounces
150 pounds 65 ounces
200 pounds 70 ounces

If you would like to calculate your body weight and daily fluid requirements using the metric system, please use this formula.

  • For the first 10kg (kilogram) of body weight the daily fluid intake required is 100cc per kg.

  • For the next 10kg of body weight, the fluid required is an additional 50 cc/kg.

  • For every additional kg of body weight, an additional 10cc/kg

The body is able to monitor the amount of fluid it needs to function. The thirst mechanism signals the body to drink water when the body is dry. As well, hormones like anti-diuretic hormone (ADH) work with the kidney to limit the amount of water lost in the urine when the body needs to conserve water.

Dynamic Picture of Rehydration

Dynamic Picture of Dehydration

What causes dehydration?

Dehydration occurs because there is too much water lost, not enough water taken in, or most often a combination of the two.

  • Diarrhea: Diarrhea is the most common reason for a person to lose excess amounts of water. A significant amount of water can be lost with each bowel movement. Worldwide, more than four million children die each year because of dehydration from diarrhea.

  • Vomiting: Vomiting can also be a cause of fluid loss. It is lost in the vomitus, but it is difficult for a person to replace water by drinking it if they have nausea and are unable to tolerate liquids.

  • Sweat: The body can lose significant amounts of water when it tries to cool itself by sweating. Whether the body is hot because of the environment (for example, working in a warm environment), intense exercising in a hot environment, or because a fever is present due to an infection; the body uses water in the form of sweat to cool itself. Depending upon weather conditions, a brisk walk may generate up to 16 ounces of sweat (a pound of water) to allow body cooling, and that water needs to be replaced by the thirst mechanism signaling the person to drink fluids.

  • Diabetes: In people with diabetes, elevated blood sugar levels cause sugar to spill into the urine and water then follows, which may cause significant dehydration. For this reason, frequent urination and excessive thirst are among the early symptoms of diabetes.

  • Burns: The skin acts as a protective barrier for the body and is also responsible for regulating fluid loss. Burn victims become dehydrated because the damaged skin cannot prevent fluid from seeping out of the body. Other inflammatory diseases of the skin are also associated with fluid loss.

  • Inability to drink fluids: The inability to drink adequately is the other potential cause of dehydration. Whether it is the lack of availability of water, intense nausea with or without vomiting, or the lack of strength to drink, this, coupled with routine or extraordinary water losses can compound the degree of dehydration.


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Dehydration

What is Staphylococcus?

Staphylococcus is a group of bacteria that can cause a number of diseases as a result of infection of various tissues of the body. Staphylococcus is more familiarly known as Staph (pronounced "staff"). Staph-related illness can range from mild and requiring no treatment to severe and potentially fatal.

The name Staphylococcus comes from the Greek staphyle, meaning a bunch of grapes, and kokkos, meaning berry, and that is what Staph bacteria look like under the microscope, like a bunch of grapes or little round berries. (In technical terms, these are gram-positive, facultative anaerobic, usually unencapsulated cocci.)

Over 30 different types of Staphylococci can infect humans, but most infections are caused by Staphylococcus aureus. Staphylococci can be found normally in the nose and on the skin (and less commonly in other locations) of 25%-30% of healthy adults. In the majo...

Read the Staph Infection (Staphylococcus Aureus) article »







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