DESCRIPTION

• Dehydration is a pathologic state of negative fluid balance in the body. Severity is generally expressed as a percentage of body weight.
  • Mild, moderate, and severe dehydration correspond to volume loss of <5%, 5–10%, and >10%, respectively.
  • Dehydration can also be classified as isotonic (sodium [Na] 130 to 150 mmol/L), hypotonic (Na <130 mmol/L), or hypertonic (Na >150 mmol/L).
• Dehydration can be the result of a wide range of illnesses.
• Accurate clinical recognition and classification of dehydration determines rehydration treatment options.

EPIDEMIOLOGY

• Globally, dehydration from diarrheal illness is one of the leading causes of mortality in children <5 years old.
• Incidence of moderate to severe dehydration in the United States has declined since the introduction of routine rotavirus immunization.
• Despite a reduction in morbidity attributed to routine rotavirus vaccination, 200,000 children per year are hospitalized in the United States for dehydration from diarrheal illness.

ETIOLOGY

• Common sources of fluid loss include
  • GI losses: vomiting, diarrhea (most common cause of dehydration in pediatric patients)
  • Renal losses: diabetes mellitus, diabetes insipidus, diuretics
  • Insensible losses: sweating, fever, tachypnea, increased ambient temperature, large burns
• Common causes of intravascular hypovolemia from fluid movement to extracellular compartment known as third-spacing include
  • Children with renal disease and edema such as in nephrotic syndrome, heart disease such as congestive heart failure, liver disease, malnutrition, and capillary leakage seen in systemic inflammation or sepsis.
• Common causes of inadequate fluid intake include
  • Pain from stomatitis, pharyngitis, herpangina, oral trauma
  • Anorexia or malaise
  • Altered mental status
  • Inadequate access to fluids or neglect

PATHOPHYSIOLOGY

Dehydration is caused by either excessive fluid and salt losses, intracellular fluid shift to tissues, or inadequate intake of fluids.