What is dehydration?

The majority of the body is made up of water, with up to 75% of the body's weight due to H2O. Most of the water is found within the cells of the body (intracellular space). The rest is found in the so-called extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).

Total body water = intracellular space + intravascular space + 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,
• As humidified air leaves the body,
• When we sweat to cool the body, and
• When we urinate or have a bowel movement to rid the body of waste products.

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

If intravascular (within the blood vessels) water is lost, the body can compensate somewhat by shifting water from cells into the blood vessels, but this is a very short-term solution. Signs and symptoms of dehydration will occur quickly if the water is not replenished.

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.

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 a person loses excess 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; as well, it makes it difficult to replace water by drinking it.

 

• 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 a significant amount of water in the form of sweat to cool itself. Depending upon weather conditions, a brisk walk will generate up to 16 ounces of sweat (a pound of water).

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

• Burns: Burn victims become dehydrated because water seeps into the damaged skin. 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 or the lack of strength to drink adequate amounts, this, coupled with routine or extraordinary water losses, can compound the degree of dehydration.

How is dehydration treated?

As is often the case in medicine, prevention is the important first step in the treatment of dehydration. (Please see the home treatment and prevention sections.)

Fluid replacement is the treatment for dehydration. This may be attempted by replacing fluid by mouth, but if this fails, intravenous fluid (IV) may be required. Should oral rehydration be attempted, frequent small amounts of clear fluids should be used.

Clear fluids include:

 

• water,
• clear broths,
• popsicles,
• Jell-O, and
• other replacement fluids that may contain electrolytes (Pedialyte, Gatorade, Powerade, etc.)

Decisions about the use of intravenous fluids depend upon the healthcare provider's assessment of the extent of dehydration and the ability for the patient to recover from the underlying cause.

The success of the rehydration therapy can be monitored by urine output. When the body is dry, the kidneys try to hold on to as much fluid as possible, urine output is decreased, and the urine itself is concentrated. As treatment occurs, the kidneys sense the increased fluid and urine output increases.

Medications may be used to treat underlying illnesses and to control fever, vomiting, or diarrhea.
 

Can I treat dehydration at home?

Dehydration occurs over time. If it can be recognized in its earliest stages, and if its cause can be addressed, then home treatment may be adequate.

Steps a person can take at home to prevent severe dehydration include:

• Patients with vomiting and diarrhea can try to alter their diet and use medications to control symptoms to minimize water loss.

•  Acetaminophen or ibuprofen may be used to control fever.

• Fluid replacements may be attempted by replacing fluid by mouth with frequent small amounts of clear fluids (see clear fluids information in previous section).

If the patient becomes confused or lethargic; if there is persistent, uncontrolled fever, vomiting, or diarrhea; or if there are any other specific concerns, then medical care should be accessed.



Written by Medpages Editorial Team
Last Editorial Review: 25/1/2010