Dehydration
BASICS
DESCRIPTION
- Dehydration is defined as a deficiency in total body water (1).
- There are two types of dehydration:
- Hypertonic: an uncompensated, predominant water deficit
- Isotonic: a deficiency of water with an associated reduction in salt
EPIDEMIOLOGY
Dehydration is linked to higher mortality and morbidity, prevalent in many health care settings and responsible for nearly 10% of pediatric hospitalizations in the United States (1),(2).
Incidence
Dehydration occurs in 17% to 28% of older adults in the United States.
Prevalence
Several retrospective studies have evaluated dehydration prevalence after hospital admission, estimating that 2.1–3.5% of patients meet dehydration criteria (1).
ETIOLOGY AND PATHOPHYSIOLOGY
- Body water can be lost through the skin (sweating, burns), lungs (pulmonary issues), kidneys (diuresis), and gastrointestinal tract (vomiting, diarrhea, bleeding).
- A negative fluid balance, where losses exceed intake, can cause hypovolemia and end-organ damage.
- “Third spacing” of fluids may occur with effusions, ascites, capillary leaks, or sepsis.
Geriatric Considerations
Elderly individuals face higher risks due to decreased kidney function, urine concentration, aldosterone secretion, vasopressin release, and renin activity. Increased immobility, fall risk, and impaired thirst mechanisms also contribute to these risks.
Genetics
Some dehydration cases are genetic (e.g., diabetes), although others are not (e.g., gastroenteritis).
RISK FACTORS
- Very young children and the elderly are most vulnerable.
- Acute or chronic illness
- Decreased cognition or mental status
- Lack of access to water
- Increased exertion (work or exercise) in hot or outdoor settings
- Medication exposure (e.g., diuretics)
GENERAL PREVENTION
- Educate patients/parents on early dehydration signs.
- Offer preferred beverages, especially during illness.
- Follow universal precautions (e.g., hand hygiene).
- Hydrate well before and after strenuous activity or extreme weather.
| Clinical Finding | Mild | Moderate | Severe |
|---|---|---|---|
| Dehydration: children | 5–10% | 10–15% | >15% |
| Dehydration: adults | 3–5% | 5–10% | >10% |
| General condition: infants | Thirsty, alert, restless | Lethargic/drowsy | Limp, cold, cyanotic extremities, may be comatose |
| General condition: older children | Thirsty, alert, restless | Alert, postural dizziness | Apprehensive, cold, cyanotic extremities, muscle cramps |
| Quality of radial pulse | Normal | Thready/weak | Feeble or impalpable |
| Quality of respiration | Normal | Deep | Deep and rapid/tachypnea |
| BP | Normal | Normal to low | Low (shock) |
| Skin turgor | Normal skin turgor | Reduced skin turgor, cool skin | Skin tenting, cool, mottled, acrocyanotic skin |
| Eyes | Normal | Sunken | Very sunken |
| Tears | Present | Absent | Absent |
| Mucous membranes | Moist | Dry | Very dry |
| Urine output | Normal | Reduced | None passed in many hours |
| Anterior fontanelle | Normal | Sunken | Markedly sunken |
COMMONLY ASSOCIATED CONDITIONS
- Hypernatremia/hyponatremia
- Hypokalemia
- Hyperglycemia
- Hypovolemic shock
- Renal failure
- Rhabdomyolysis
- Heat-related illness or injury
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