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The most common disorder of fluid balance in children requiring emergency care is dehydration. Dehydration is the result of a negative fluid balance that can result from decreased fluid intake, increased output (renal, GI, or insensible losses from the skin or respiratory tract), or conditions such as sepsis, burns, and diabetes.


The presence of fluid and electrolyte disturbances is often suggested by a thorough history. Children with chronic underlying disease are at particular risk. The clinical appearance depends on the degree of dehydration, the rate at which the fluid was lost, and the age of the patient.

Though the gold standard for assessing dehydration is comparison of pre-illness weight with weight on presentation to the emergency department (ED), a reliable and recent pre-illness weight is rarely available in the ED. Physical examination can provide an estimation of the degree of dehydration, which is typically classified as mild, moderate, or severe. Clinical signs and symptoms of dehydration are listed in Table 81-1. An important exception to the reliability of signs and symptoms to predict degree of dehydration occurs in hypernatremic dehydration, when fluid loss occurs primarily from the interstitial and intracellular spaces and clinical signs of intravascular volume depletion may be minimal. In this setting, however, the skin may have a characteristic doughy feel.

Table 81-1

Clinical Guidelines for Assessing Dehydration in Children


If available, the absolute and relative fluid deficit can be calculated from a pre-illness weight: 1 kg of weight loss is equivalent to 1 L of fluid deficit. In the absence of a reliable pre-illness comparison weight, the diagnosis of dehydration is based primarily on historical data and physical examination findings (Table 81-1).

Routine laboratory testing is not required in mild to moderate dehydration, but serum electrolytes and other studies may be indicated in the setting of severe dehydration, signs and symptoms of electrolyte abnormalities, or certain underlying medical conditions. A rapid bedside glucose test should be done on any child presenting with altered sensorium. Infants are at particular risk of hypoglycemia.

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