Dehydration means the body does not have enough fluids to function at an optimal level. Dehydration can be caused by fluid loss (through vomiting, diarrhea or excessive urination), inadequate intake, or a combination of both. The most common cause of dehydration in infants and children is acute gastroenteritis , with its associated vomiting and diarrhea. Dehydration is classified as mild, moderate, or severe based on the percentage of body weight lost during the acute illness: Depending on age,

Mild dehydration

-- a loss of 3-5% of body weight

Moderate dehydration

-- a loss of 6-10% of body weight

Severe dehydration

-- a loss of more than 9-15% of body weight. This is a life-threatening emergency!

Causes, incidence, and risk factors

Because of their smaller body weights and higher turnover rates for water and electrolytes, infants and children are more susceptible to dehydration than adults. Causes of dehydration include excessive fluid losses, inadequate fluid intake, or a combination of these factors. Causes of acute fluid loss include:

vomiting

diarrhea

(especially well recognized in

cholera )

excessive urine output (

polyuria ) such as with uncontrolled diabetes

sweating, excessive

fever

Dehydration can also occur from inadequate intake as in:

nausea

refusing to drink because of mouth sores (

stomatitis ) or a sore throat ( pharyngitis )

acute

illness with

loss of appetite Dehydration in children is most often a combination of both as in:

gastroenteritis with vomiting and diarrhea

acute illness where the child refuses fluids and loses excessive fluid through

sweating with fever

Signs and tests

A physical examination may also show signs of:

low blood pressure

(hypotension)

rapid heart rate

(tachycardia)

delayed capillary refill

shock

Tests include:

blood chemistries

(to check

electrolytes , especially sodium, potassium, and bicarbonate levels)

urine specific gravity

(a high specific gravity indicates significant dehydration)

BUN

(blood urea nitrogen -- may be elevated with dehydration)

creatinine

(creatinine -- may be elevated with dehydration)

Complete Blood Count (CBC) to look for signs of concentrated blood (hemoconcentration)

Other tests may be done to determine the specific cause of the dehydration (for example, a blood sugar to check for diabetes ).

Treatment

Drinking fluids is often sufficient for mild dehydration. It is better to encourage frequent, small amounts of fluid (using a teaspoon or syringe) rather than forcing a child to drink a large amount of fluid at one time. Intravenous fluids and hospitalization may be necessary for moderate to severe dehydration. The health care provider must also determine and, if possible, treat the cause of the dehydration. The great majority of cases of acute gastroenteritis are caused by viruses. They tend to be self-limited, resolving on their own after a few days.

Expectations (prognosis)

When dehydration is recognized and treated promptly, the outcome is generally good.

Complications

Untreated severe dehydration may result in seizures , permanent brain damage, or death.

Calling your health care provider

Call your health care provider if you suspect dehydration. Remember that a child can quickly become severely dehydrated.

Prevention

It is important to carefully monitor hydration status any time an infant or child is ill. If you believe that dehydration is developing, consult a health care provider before the child becomes moderately or severely dehydrated. A few simple measures may prevent the development of severe dehydration. Always encourage fluids during an illness, and remember that fluid needs are increased with fever, vomiting, and diarrhea. The easiest signs to monitor are urine output (there should be frequent wet diapers or trips to the bathroom), saliva in the mouth, and tears with crying. Avoid using water as the primary replacement fluid, especially in infants. Specific solutions (such as Pedialyte) are available that provide the right amount of electrolytes to prevent electrolyte abnormalities.