• A state of negative fluid balance; strictly defined as free water deficiency
  • The two types of dehydration:
    • Water loss
    • Salt and water loss (combination of dehydration and hypovolemia)


  • Responsible for 10% of all pediatric hospitalizations in the United States
  • Gastroenteritis, one of its leading causes, accounts to 13/1,000 children <5 years of age annually in the United States.


  • More than half a million hospital admissions annually in the United States for dehydration
  • Of hospitalized older persons, 8% are dehydrated (1).
  • Worldwide, ~3 to 5 billion cases of acute gastroenteritis occur each year in children <5 years of age, resulting in nearly 2 million deaths.

Etiology and Pathophysiology

  • Negative fluid balance occurs when ongoing fluid losses exceed fluid intake.
  • Fluid losses can be insensible (sweat, respiration), obligate (urine, stool), or abnormal (diarrhea, vomiting, osmotic diuresis in diabetic ketoacidosis).
  • Negative fluid balance can lead to severe intravascular volume depletion (hypovolemia) and end-organ damage from inadequate perfusion.
  • The elderly are at increased risk as kidney function, urine concentration, thirst sensation, aldosterone secretion, release of vasopressin, and renin activity are all significantly lowered with age.
  • Decreased intake
  • Increased output: vomiting, diarrheal illnesses, sweating, frequent urination
  • “Third spacing” of fluids: effusions, ascites, capillary leaks from burns, or sepsis

Some causes of dehydration have a genetic component (diabetes), whereas others do not (gastroenteritis).

Risk Factors

  • Children <5 years of age at highest risk
  • Elderly
  • Decreased cognition
  • Lack of access to water such as in critically sick intubated patients
  • Increased exertion in high temperature

General Prevention

  • Patient/parent education on early signs of dehydration
  • Universal precautions (including hand hygiene)

Geriatric Considerations
Systematically assessing risk factors helps with early prevention and management of dehydration in the elderly, especially those in long-term care facilities.

Clinical FindingMildModerateSevere
Dehydration: children5–10%10–15%>15%
Dehydration: adults3–5%5–10%>10%
General condition: infantsThirsty, alert, restlessLethargic/drowsyLimp, cold, cyanotic extremities, may be comatose
General condition: older childrenThirsty, alert, restlessAlert, postural dizzinessApprehensive, cold, cyanotic extremities, muscle cramps
Quality of radial pulseNormalThready/weakFeeble or impalpable
Quality of respirationNormalDeepDeep and rapid/tachypnea
BPNormalNormal to lowLow (shock)
Skin turgorNormal skin turgorReduced skin turgor, cool skinSkin tenting, cool, mottled, acrocyanotic skin
EyesNormalSunkenVery sunken
Mucous membranesMoistDryVery dry
Urine outputNormalReducedNone passed in many hours
Anterior fontanelleNormalSunkenMarkedly sunken

Commonly Associated Conditions

  • Hypo-/hypernatremia
  • Hypokalemia
  • Hypovolemic shock
  • Renal failure
  • Rhabdomyolysis
  • Heat illness

There's more to see -- the rest of this topic is available only to subscribers.