Patient education: Dehydration and hypovolemia in adults (The Basics)

What are dehydration and hypovolemia? — 

These both describe a problem with the body's balance of fluids and electrolytes. (Electrolytes are substances, including sodium and potassium, the body needs to work properly.) But the 2 terms mean slightly different things:

●Dehydration – This means loss of water only, or not getting enough water to balance the body's salt. It can cause the body's salt, or "sodium," level to be too high.

●Hypovolemia – This is when the overall amount of fluid in the body (including water, blood, and other fluids) is too low. Most of the fluid in the body contains salt. So with hypovolemia, the body has too little of both water and salt.

People often use the term "dehydration" for any type of water or fluid loss. But it is technically different from hypovolemia, and is treated differently.

What causes dehydration? — 

When a person does not have enough water, possible causes include:

●Health conditions that make the body lose much more water than normal through urine

●Not drinking enough water to make up for what the body loses normally – This can happen if a person does not realize they are thirsty, either because of a medical problem or because they cannot think clearly.

What causes hypovolemia? — 

It's normal for people to lose some water and salt every day, for example, through urine and bowel movements. But it's possible to lose too much water and salt if you:

●Have vomiting or diarrhea

●Sweat a lot, for example, from heavy exercise in hot weather

●Take medicines that cause you to urinate more than usual, called "diuretics"

If you cannot take in enough water and salt to make up for what your body lost, it can lead to problems.

What are the symptoms of dehydration? — 

The main symptom is feeling thirsty. Thirst is the body's way of telling you when you need water.

If a person is dehydrated and cannot drink water or does not realize they are thirsty, the level of sodium in their body can get too high. This is called "hypernatremia." It can cause symptoms like:

●Feeling tired, weak, or irritable

●Twitching

●Seizures or coma

Higher sodium levels can cause more serious symptoms, including brain damage, if not treated quickly.

What are the symptoms of hypovolemia? — 

Early symptoms can include:

●Feeling very tired

●Thirst

●Muscle cramps

●Dry mouth

●Skin that is less elastic than usual (for example, does not flatten out right away after you pinch it)

●Feeling dizzy when standing up

●Urinating less often than usual

If hypovolemia is severe, it can cause other symptoms, such as:

●Belly pain

●Chest pain

●Confusion

Will I need tests? — 

Maybe. If you lost a lot of fluid and have any of the above symptoms, call your doctor or nurse. They can tell you if you need to be seen. Depending on your situation, they might do blood or urine tests. This can help them figure out what is causing your symptoms and how best to treat it.

How is dehydration treated? — 

Most people who get mildly dehydrated can correct it by drinking water when they feel thirsty. This helps return the body's water and salt balance to normal.

If a person has been unable to drink and their sodium level is too high, they need treatment in the hospital. Doctors can give a water solution through a thin tube that goes into a vein, called an "IV." They will do tests to monitor the level of sodium in the person's blood. This way, they can make sure the person gets the right amount of water to balance it out.

How is hypovolemia treated? — 

You might get better on your own once you stop losing water and salt.

If you do need treatment, it involves giving your body water and salt to make up for what it lost. In mild cases, you might be able to do this on your own by:

●Drinking liquids that contain salt – Examples include "oral rehydration solutions" and broth. Try drinking small amounts every 15 to 30 minutes.

●Eating when you are able – Good choices include lean meats, fruits, vegetables, and whole-grain breads and cereals. If you drink a lot of plain water, it's especially important to make sure you are also eating. This will help your body keep the right salt and water balance.

Some people follow a low-salt diet, for example, to help control their blood pressure. If you normally limit or avoid salt, stop doing this while you recover. It's important to replace the salt your body lost. Your doctor will tell you when to go back to your usual diet.

In severe cases, a person might need treatment in the hospital. This involves getting special fluids through an IV. This helps get the body's level of water and salt back to normal.

When should I call the doctor? — 

Call for emergency help (in the US and Canada, call 9-1-1) if you:

●Feel very weak, like you can't stand up, and your skin is cool, is clammy, or looks blue or gray

●Have severe belly pain

●Have chest pain or trouble breathing

●Pass out

●Do not urinate for more than 8 hours

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