Dehydration

This page is for adult patients. For pediatric patients, see: dehydration (peds)

Background

• Decreased total body water resulting in relative hypertonicity and hypernatremia
• Usually resulting from inadequate fluid intake or increased free water loss
• Often confused with hypovolemia in which total body water is lost with a relative hypotonic or isotonic state

Clinical Features

• dry mucous membranes
• skin tenting
• sunken eyes
• excessive thirst
• headache
• dizziness
• altered mental status
• weakness
• fatigue
• dark urine or decreased urine output
• syncope
• hemodynamic instability

Differential Diagnosis

Causes of sinus tachycardia

• Emotional or psychiatric causes
  • Pain, anger, or anxiety
• Response to fever (about 10 bpm per degree C > 37.0)
• SIRS (from infection or other causes)
• Dehydration/hypovolemia
• Anemia
• Drug/alcohol intoxication (particularly sympathomimetic or anticholinergic drugs, but may also be seen in aspirin, theophylline, or other ingestions)
• Drug/alcohol withdrawal
• Anion gap acidosis
• Hyperthyroidism
• PE
• CHF
• Cardiac tamponade
• Myocardial contusion
• Cardiac valvular disease
• Hyper or hypoglycemia
• Myocardial infarction
• Pheochromocytoma

Evaluation

• Urine sodium concentration
• FENa (fractional excretion of sodium)
• Urine osmolality
• Urinalysis

See Also

• Dehydration (peds)
• Hypovolemia
• IV fluid resuscitation

Calculators

Maintenance Fluids (4-2-1 Rule)

Maintenance IV Fluids (4-2-1 Rule)

Parameter	Value
Patient Weight (kg)
Maintenance Rate
Hourly Rate	mL/hr
Daily Volume	mL/day

References
Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832. PMID 13431307. 4-2-1 Rule: 4 mL/kg/hr for first 10 kg + 2 mL/kg/hr for next 10 kg + 1 mL/kg/hr for each kg above 20 kg.