What is moderate dehydration?

Moderate Dehydration: Definition and Clinical Assessment

Moderate dehydration is characterized by a 6-9% fluid deficit and is associated with loss of skin turgor, tenting of skin when pinched, and dry mucous membranes. 1

Clinical Signs of Moderate Dehydration

General Assessment

• Fluid deficit of 6-9% of body weight 1
• Loss of skin turgor
• Skin tenting when pinched
• Dry mucous membranes

Additional Signs in Various Populations

• In children with vomiting or diarrhea: At least four of the following seven signs indicate moderate to severe volume depletion 1:

  • Confusion
  • Non-fluent speech
  • Extremity weakness
  • Dry mucous membranes
  • Dry tongue
  • Furrowed tongue
  • Sunken eyes

• In infants and young children:

  • Capillary refill time >2 seconds (when combined with decreased urine output, absent tears, dry mucous membranes, and generally ill appearance) 1
  • Note: Capillary refill time is influenced by ambient temperature, site, age, and lighting conditions 1

Diagnostic Approach

Clinical Assessment

• Visual examination to confirm abnormal consistency of stool and presence of blood or mucus (in cases of diarrhea) 1
• Accurate body weight measurement (acute weight change is the most accurate assessment of fluid status) 1
• Auscultation for adequate bowel sounds before initiating oral therapy 1

Laboratory Assessment

• Serum electrolytes may be measured when abnormal sodium or potassium concentrations are suspected 1
• Serum osmolality >300 mOsm/kg (or calculated osmolarity >295 mmol/L) indicates severe dehydration requiring intervention 1

Management Principles

Rehydration Phase

• Replace fluid deficit to attain clinical hydration 1
• For moderate dehydration from vomiting or diarrhea, isotonic fluids should be administered orally, nasogastrically, subcutaneously, or intravenously 1
• Oral rehydration therapy is preferred when possible, especially for children 2

Maintenance Phase

• Maintain adequate dietary and fluid intake 1
• Replace ongoing excess fluid losses continuously 1
• For infants with diarrhea, continue breastfeeding or formula feeding during episodes of loose stools 2

Important Considerations

• Dehydration assessment is more challenging in older adults, as individual clinical signs and bedside tests may be poor diagnostic tools 3
• There are two main types of dehydration: water loss dehydration (hyperosmolar) and salt and water loss dehydration (hyponatremia) 4
• Moderate dehydration requires prompt intervention to prevent progression to severe dehydration, which can lead to significant morbidity and mortality 5

Common Pitfalls to Avoid

1. Confusing "dehydration" with "hypovolemia" - these terms are often incorrectly used interchangeably 5
2. Relying on a single clinical sign for diagnosis - a combination of signs provides better diagnostic accuracy 5
3. Failing to recognize dehydration in older adults due to atypical presentations 3
4. Overlooking the need to replace ongoing fluid losses during both rehydration and maintenance phases 1

Moderate dehydration represents a significant clinical concern that requires prompt recognition and appropriate management to prevent progression to more severe states and associated complications.