Dehydration (exsiccosis) is a state of decreased total body water. This decrease in total body water occurs in excess of sodium (also called “free water loss”), resulting in a hypertonic and hypernatremic state. The terms “hypotonic” and “isotonic” are sometimes incorrectly used to describe dehydration, but these terms are only associated with hypovolemia and . Dehydration most often affects children and the elderly. Treatment of dehydration involves correcting the free water deficit.
- Insufficient water intake, particularly in elderly individuals and the critically ill
- Increased free water loss
- See also and .
- Dry skin and mucous membranes
- Headache, dizziness, disorientation
- Weakness, fatigue, hemodynamic instability
- Dark circles around the eyes and frequent blinking (reduced tear fluid quantity)
- Children: no tears when crying
- Infants: sunken fontanelle, restlessness/lethargy
|Clinical feature||Mild dehydration||Moderate dehydration||Severe dehydration|
|Decrease in body weight||< 3%||3–9%|| |
|Symptoms||Mental status||Alert||Restless, irritable||Lethargic, confused|
|Thirst||Slightly increased||Thirsty; drinks eagerly||Refuses to drink|
|Urine output||Normal||↓ (dark concentrated urine)||↓↓|
|Signs specific to dehydration||Eyes||Normal||Slightly sunken||Significantly sunken|
|Tears (especially children)||Normal||Decreased||Absent|
|Skin turgor||Instant recoil||Recoil within 2 seconds||Recoil after 2 seconds; significant skin tenting|
|In infants: anterior fontanelle||Normal||Slightly sunken||Significantly sunken|
|Signs of hypovolemia and||Pulse rate||Normal||Mildly tachycardic||Initially tachycardia → later bradycardia|
|Blood pressure||Normal||Normal; postural hypotension may be present||Hypotension|
|Capillary refill time||Normal (< 2 seconds)||2–3 seconds||> 3 seconds|
|Breathing||Normal||Tachypnea||Tachypnea with deep breathing|
- Serum sodium:
- Serum sodium levels can be used to determine the amount of free fluid needed to correct dehydration (see ).
- ↑ Hematocrit
- ↓ Serum bicarbonate levels
- BUN to serum creatinine ratio > 20:1 → renal hypoperfusion due to hypovolemia
: See for more information.
- < 800 mOmol/L → renal free water loss
- > 800 mOmol/L → extrarenal free water loss
- Blood glucose levels
- Severe hypovolemia
- Moderate hypovolemia
- Children: consider oral hydration therapy or 10 mL/kg of isotonic saline → reassess → repeat as needed
- Correction of electrolyte abnormalities
- should only be addressed once the patient is adequately resuscitated.
- prerenal renal failure →
- Increased risk of infection, particularly of the urinary tract
- Osmotic demyelination syndrome
- Patients with diabetes mellitus: Dehydration can trigger diabetic ketoacidosis.
We list the most important complications. The selection is not exhaustive.