How to hydrate a dehydrated patient?

How to Hydrate a Dehydrated Patient

Immediate Assessment-Based Algorithm

The approach to hydration depends entirely on the severity of dehydration: use oral rehydration solution (ORS) with reduced osmolarity for mild-to-moderate dehydration, and reserve intravenous isotonic fluids exclusively for severe dehydration with shock, altered mental status, or inability to tolerate oral intake. 1

Step 1: Rapidly Assess Dehydration Severity

Categorize the patient immediately using these clinical markers:

Mild Dehydration (3-5% fluid deficit): 2

• Slightly decreased urine output
• Normal mental status
• Moist mucous membranes
• Normal skin turgor 1

Moderate Dehydration (6-9% fluid deficit): 2

• Markedly decreased urine output
• Dry mucous membranes
• Loss of skin turgor with tenting
• Sunken eyes 1

Severe Dehydration (≥10% fluid deficit): 2

• Severe lethargy or altered consciousness
• Prolonged skin tenting (>2 seconds)
• Cool, poorly perfused extremities
• Decreased capillary refill
• Rapid, deep breathing (acidosis)
• Minimal to no urine output 1

For older adults specifically, measured serum osmolality >300 mOsm/kg confirms dehydration. 1

Step 2: Match Treatment to Severity

Mild-to-Moderate Dehydration: Oral Rehydration First-Line

Use reduced osmolarity ORS (50-90 mEq/L sodium) as the definitive first-line therapy. 1 This prevents 93% of diarrhea deaths and is superior to intravenous therapy for patients who can tolerate oral intake. 3

Dosing Protocol:

• Mild dehydration: 50 mL/kg over 2-4 hours 2, 4
• Moderate dehydration: 100 mL/kg over 2-4 hours 2, 4

Administration technique: Start with small volumes (one teaspoon) using a teaspoon, syringe, or medicine dropper, then gradually increase as tolerated. 2, 4 For vomiting patients, begin with 5 mL aliquots and advance slowly. 4

Replace ongoing losses concurrently:

• Children <10 kg: 60-120 mL ORS per diarrheal stool or vomiting episode 4
• Children >10 kg: 120-240 mL ORS per episode 4
• Alternative calculation: 10 mL/kg per watery stool, 2 mL/kg per vomiting episode 4

Critical pitfall: Do NOT use apple juice, Gatorade, soft drinks, or chicken broth for rehydration—these have inappropriate electrolyte content and high osmolality that worsens diarrhea. 4, 5 Only use commercially available ORS formulations. 4

If Oral Route Fails

Consider nasogastric ORS administration at 15 mL/kg/hour for patients who cannot drink adequately but are not in shock. 1, 4 This is particularly effective in infants and should be attempted before escalating to IV therapy. 1

Severe Dehydration: Immediate Intravenous Therapy

Severe dehydration constitutes a medical emergency requiring immediate IV rehydration with isotonic crystalloids (lactated Ringer's or normal saline). 1

IV Protocol:

• Administer 20 mL/kg boluses rapidly 2, 1, 4
• Repeat boluses until pulse, perfusion, and mental status normalize 2, 1
• May require two IV lines or alternate access (venous cutdown, femoral vein, intraosseous) 2
• Total rehydration volume approximately 100 mL/kg 4

Exception for malnourished patients: Use smaller 10 mL/kg boluses given more frequently due to reduced cardiac capacity. 4

Transition strategy: Once the patient's consciousness returns to normal and vital signs stabilize, transition to oral ORS to complete rehydration. 2, 4 This hybrid approach is faster and more physiologic than IV alone. 1

Step 3: Reassess at 2-4 Hours

Mandatory reassessment after the initial rehydration period: Check skin turgor, mucous membranes, urine output, mental status, and vital signs. 2, 4

• If rehydrated: Progress to maintenance phase 2
• If still dehydrated: Re-estimate fluid deficit and restart rehydration therapy 2, 4
• If worsening: Escalate to IV therapy or seek immediate medical attention 4

Maintenance Phase After Rehydration

Resume age-appropriate diet within 3-4 hours after achieving rehydration. 4 Continue breastfeeding throughout in infants. 1, 4 Replace ongoing losses with ORS until diarrhea and vomiting resolve. 1

Do not use anti-diarrheal medications in children with acute diarrhea. 4

Special Population: Exertional Dehydration

For athletes and exercise-induced dehydration without shock or confusion, use 5-8% carbohydrate-electrolyte solutions containing 20-30 mEq/L sodium. 2, 5 Alternatives include coconut water or 2% milk if CE drinks are unavailable; potable water is acceptable as a last resort. 2 Lemon tea-based CE drinks and Chinese tea with caffeine are equivalent to water. 2

Special Population: Older Adults

For older adults appearing well, encourage increased fluid intake with preferred beverages. 1 For those appearing unwell, offer subcutaneous or intravenous fluids in parallel with oral intake—subcutaneous dextrose infusions are as effective as IV with similar adverse effect rates. 1

Red Flags Requiring Immediate Medical Attention

• Inability to keep down any fluids for >24 hours 1
• Severe postural dizziness preventing standing 1
• Confusion or altered mental status 1
• Persistent high fever 1
• Frank blood in vomit or stool 1
• No urine output for 6-8 hours 6