How is dehydration evaluated and treated?

Evaluation and Treatment of Dehydration

Dehydration should be assessed through clinical evaluation of physical signs and symptoms, with treatment tailored to the severity of fluid deficit through a two-phase approach of rehydration followed by maintenance therapy. 1

Assessment of Dehydration

Clinical Evaluation

The degree of dehydration should be determined through careful physical examination:

• Mild dehydration (3-5% fluid deficit): Increased thirst and slightly dry mucous membranes 1
• Moderate dehydration (6-9% fluid deficit): Loss of skin turgor, tenting of skin when pinched, and dry mucous membranes 1
• Severe dehydration (≥10% fluid deficit): Severe lethargy or altered consciousness, prolonged skin tenting (>2 seconds), cool and poorly perfused extremities, and decreased capillary refill 1

Most Reliable Clinical Signs

• Rapid, deep breathing (indicating acidosis), prolonged skin retraction time, and decreased perfusion are more reliable indicators of dehydration than sunken fontanelle or absence of tears 1
• Capillary refill time correlates with fluid deficit, though fever, ambient temperature, and age can affect this measurement 1

Laboratory Assessment

• Supplementary laboratory studies are rarely needed for routine cases 1
• Serum electrolytes should be measured when clinical signs suggest abnormal sodium or potassium concentrations 1
• Plasma osmolality >300 mOsm/kg indicates hyperosmolar dehydration 2

Treatment Approach

Phase 1: Rehydration

Treatment should be based on the degree of dehydration:

Mild Dehydration (3-5% fluid deficit)

• Administer oral rehydration solution (ORS) containing 50-90 mEq/L of sodium 1
• Give 50 mL/kg over 2-4 hours 1
• Start with small volumes (one teaspoon) and gradually increase as tolerated 1
• Reassess hydration status after 2-4 hours 1

Moderate Dehydration (6-9% fluid deficit)

• Use same ORS administration procedure as for mild dehydration 1
• Increase fluid amount to 100 mL/kg over 2-4 hours 1

Severe Dehydration (≥10% fluid deficit)

• This constitutes a medical emergency requiring immediate IV rehydration 1
• Administer boluses (20 mL/kg) of Ringer's lactate solution or normal saline until pulse, perfusion, and mental status normalize 1
• May require multiple IV access sites 1
• When consciousness returns to normal, remaining deficit can be given orally 1

Phase 2: Maintenance Therapy

Replacement of Ongoing Fluid Losses

• Replace ongoing stool and vomit losses during both rehydration and maintenance phases 1
• If measurable, give 1 mL of ORS for each gram of diarrheal stool 1
• If not measurable, give approximately 10 mL/kg for each watery stool and 2 mL/kg for each episode of vomiting 1

Dietary Recommendations

• Breast-fed infants should continue nursing on demand 1
• For bottle-fed infants, use full-strength, lactose-free, or lactose-reduced formulas immediately upon rehydration 1
• For adults and children over 4-6 months, feeding should begin as soon as appetite returns 1
• Avoid "resting the bowel" through fasting 1

Special Considerations

Home Management

For patients with mild dehydration or those being discharged after treatment:

• Children <2 years: 50-100 mL ORS after each stool 1
• Older children: 100-200 mL ORS after each stool 1
• Adults: As much as desired 1
• Increase normal fluid intake with locally available fluids (cereal-based gruels, soup, rice water) 1
• Continue feeding, especially for children 1

Warning Signs

Advise patients/caregivers to return for medical attention if the patient:

• Continues to pass many stools 1
• Is very thirsty 1
• Has sunken eyes 1
• Develops fever 1
• Does not show improvement 1

Common Pitfalls and Caveats

• Physical signs alone have poor sensitivity (0-44%) for detecting dehydration in elderly patients 3
• "Dehydration" and "hypovolemia" are incorrectly used interchangeably in clinical practice 2
• Soft drinks are not recommended for rehydration due to their high osmolality 1
• Thirst assessment using a 0-9 scale (with ≥4 indicating dehydration) can identify both intracellular and extracellular dehydration with good diagnostic accuracy 4
• Anti-diarrheal agents are contraindicated for the treatment of diarrheal disease 1