The World Health Organization defines dehydration as a condition that results from excessive loss of body water. The most common causes of dehydration in children are vomiting and diarrhea.
Infants and young children are particularly susceptible to diarrheal disease and dehydration. Reason include higher metabolic rate, inability to communicate their needs or hydrate themselves, and increased insensible losses. Other causes of dehydration may be the result of other disease processes resulting in the fluid loss which includes: diabetic ketoacidosis (DKA), diabetes insipidus, burns, excessive sweating, and third spacing. Dehydration may also be the result of decreased intake along with ongoing losses. In addition to total body water losses, electrolyte abnormalities may exist.
Dehydration is a major cause of morbidity and mortality in infants and young children worldwide. Each year approximately 760,000 children of diarrheal disease worldwide. Most cases of dehydration in children are the consequence of acute gastroenteritis.
Acute gastroenteritis in the United States is usually infectious in etiology. Viral infections, including rotavirus, norovirus, and enteroviruses cause 75 to 90 percent of infectious diarrhea cases. Bacterial pathogens cause less than 20 percent of cases. Common bacterial causes include Salmonella, Shigella, and Escherichia coli. Approximately 10 percent of bacterial disease occurs secondary to diarrheagenic Escherichia coli. Parasites such as Giardia and Cryptosporidium account for less than 5 percent of cases.
Dehydration causes a decrease in total body water in both the intracellular and extracellular fluid volumes. Volume depletion closely correlates with the signs and symptoms of dehydration.
Various sign and symptoms can be present depending on the patient's degree of dehydration. Dehydration is categorized as mild (3% to 5%), moderate (6% to 10%), and severe ( more than 10%). The table below can assist with categorizing the patient's degree of dehydration.
Dehydration% Mild 3% to 5% Moderate 6% to 10% Severe >10%
Mental status Normal Listless, irritable Altered mental
Heart rate Normal Increased Increased
Pulses Normal Decreased Thready
Capillary refill Normal Prolonged Prolonged
Blood pressure Normal Normal Decreased
Respirations Normal Tachypnea Tachypnea
Eyes Normal Slightly sunken Fewer tears
Fontanelle Normal Sunken Sunken
Urine output Normal Decreased Oliguric
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Most cases of dehydration are isonatremic. In selected cases, electrolyte abnormalities may exist. This includes derangements in sodium levels, acidosis characterized by low bicarbonate levels or elevated lactate levels. For patients with vomiting, who have not been able to tolerate oral fluids hypoglycemia may be present. Evaluation of urine specific gravity and presence of ketones can assist in the evaluation of dehydration.
End-tidal carbon dioxide measurements have been studied in an attempt to assess degrees of dehydration greater than five percent in children. This non-invasive approach has promise, but as of now has not proven to be an effective tool is determining the degree of dehydration in children.
Priorities in the management of dehydration include early recognition of symptoms, identifying the degree of dehydration, stabilization, and rehydration strategies.
Symptoms include vomiting, diarrhea, fever, decreased oral intake, inability to keep up with ongoing losses, decreased urine output, progressing to lethargy, and hypovolemic shock.
The American Academy of Pediatrics recommends oral rehydration for patients with mild dehydration. Breastfed infants should continue to nurse. Fluids with high sugar content may worsen diarrhea and should be avoided. Children can be fed age-appropriate foods frequently but in small amounts.
The Morbidity and Mortality Weekly Report recommends administering 50 mL to 100 mL of oral rehydration solutions per kilogram per body weight during two to four hours to replace the estimated fluid deficit, with additional oral rehydration solution, administered to replace ongoing losses.
For patients who are severely dehydrated, rapid restorations of fluids are required.
Patients who are severely dehydrated can present with altered mental status, lethargy, tachycardia, hypotension, signs of poor perfusion, weak thread pulses, and delayed capillary refill.
Intravenous fluids, starting with 20 ml/kg boluses of normal saline are required. Multiple boluses may be needed for children in hypovolemic shock. Additional priorities include obtaining a point of care glucose test, electrolytes, and urinalysis assessing for elevated specific gravity and ketones.
Hypoglycemia should be assessed at the point of care testing via glucometer, and venous blood gas with electrolytes or serum chemistries should be treated with intravenous glucose.
Hypoglycemia should be treated with intravenous/intraosseous glucose. The dose is 0.5 gm/km to 1 gm/km. This translates to 5 ml/kg to 10 ml/kg of D10, 2ml/kg to 4 ml/kg of D25, or 1 ml/kg to- 2 ml/kg of D50. The use of D50 is usually reserved for an adolescent or adult-sized patients using a large bore intravenous line.
Replacement of Fluids
An assessment of the degree of dehydration will determine fluid replacement. Using tables that can predict the degree of dehydration is helpful. If a previous "well weight" is available, that can be subtracted from the patient's "sick weight" to calculate total weight loss. One kilogram weight loss equates to one liter of fluid lost.
For patients where intravenous access can not be achieved or maintained, other methods can be employed. They include continuous nasogastric hydration and subcutaneous hydration.
Hypodermoclysis refers to hydrating the subcutaneous space with fluid which can be absorbed systemically. Hypodermoclysis is best reserved for the stable child or infant with mild to moderate dehydration who either fails a trial of fluids by mouth or who needs some degree of rehydration to facilitate gaining intravenous access after a slow subcutaneous fluid bolus has been given.
The process begins with:
Once the patient’s condition has stabilized, hydration therapy continues to replace existing and ongoing losses. Fluid therapy should include maintenance fluids plus replacement of the existing fluid deficit.
Deficit calculation can be determined several ways. If the patient's weight before the-illness is known, it can be subtracted from the current weight. Each kilogram lost would be equivalent to one liter of fluid lost. If the prior weight is not known, multiply the weight in kilograms by the dehydration percent.
For a 10 kg patient who is 10% dehydrated, 0.1 represents 10%
(10 kg) x (.10) = 1 kilogram
Maintenance fluids can be calculated as follows:
For patient weighing less than 10 kg, they should receive 100 mL/kg/day.
If the patient weighs less than 20 kg, fluids will include the 1000 mL/day plus 50 mL/kg/day for each kilogram between 10 kg and 20 kg.
For patients weighing more than 20 kg, give 1500 mL/day, plus 20 mL/kg/day for each kilogram over 20 kg. Divide the total by 24 to determine the hourly rate.
In hyponatremic dehydration, half of the deficit can be replaced over eight hours with the remaining half the following sixteen hours. Severe hyponatremic (< 130 mEq/L) or hypernatremic dehydration (> 150 mEq/L) is corrected over 24 to 48 hours. Symptomatic hyponatremia (seizures, lethargy) can be acutely managed with hypertonic saline (3% sodium chloride). The deficit may be calculated to restore the sodium to 130 mEq/L and administered over 48 hours, as follows:
Sodium deficit = (sodium desired - sodium actual) x volume of distribution x weight (kg))
Example: Sodium = 123, weight = 10 kg, assumed volume of distribution of 0.6; Sodium deficit = (130-123) X 0.6 X 10 kg = 42 mEq sodium. Hypertonic saline (3%) which contains 0.5 mEq/mL may be used for rapid partial correction of symptomatic hyponatremia. A bolus dose of 4 mL/kg raises the serum sodium by 3 mEq/L to 4 mEq/L.
Rapid correction of hypernatremia may result in cerebral edema, as a result of intracellular swelling occurs. Osmotic demyelination syndrome, also known as central pontine myelinolytic, can occur as a result of rapid correction of hyponatremia. Symptoms include a headache, confusion, altered consciousness, gait disturbance, and may lead to respiratory arrest.