Dehydration: Causes, Symptoms, Severity, and Treatment

Dehydration is a net negative fluid balance where water loss exceeds intake, leading to reduced total body water and impaired physiological function.

Causes

• Inadequate intake: Impaired access, dysphagia, cognitive impairment, anorexia.
• Excessive loss:
  • GI: Vomiting, diarrhea, fistulas, NG suction.
  • Renal: Diuretics, osmotic diuresis (hyperglycemia), DI.
  • Skin: Sweating (heat, fever, exercise), burns.
  • Respiratory: Hyperventilation.
  • Third-spacing: Ascites, burns, sepsis, pancreatitis.

Clinical Signs by Severity

Severity	Weight Loss	Signs
Mild (3-5%)	3-5%	Thirst, dry mouth, slightly ↓ urine output
Moderate (6-9%)	6-9%	Sunken eyes, ↓ skin turgor, tachycardia, orthostasis, oliguria
Severe (≥10%)	≥10%	Hypotension, shock, altered mental status, anuria, cold extremities

Treatment

• Oral rehydration (ORS) for mild-moderate (WHO solution: glucose + electrolytes).
• IV fluids for severe or unable to tolerate oral: isotonic crystalloids (NS, LR) bolus then maintenance.
• Correct electrolyte abnormalities (K⁺, Na⁺).
• Address underlying cause.

Prevention

Adequate fluid intake, especially in heat, illness, elderly, children. Monitor urine color/output.