Hydration Guidelines for Treating Dehydration
First-Line Treatment: Oral Rehydration Solution
Reduced osmolarity oral rehydration solution (ORS) is the first-line therapy for mild to moderate dehydration in all age groups, regardless of cause. 1, 2
Assessment of Dehydration Severity
Before initiating treatment, assess dehydration severity using clinical signs:
- Mild to moderate dehydration: Evaluate pulse, perfusion, mental status, skin turgor, and presence of sunken eyes 2
- Severe dehydration: Look for hypovolemic shock, altered mental status, rapid breathing, or inability to maintain pulse and perfusion 1
- Older adults: Measured serum or plasma osmolality >300 mOsm/kg indicates dehydration 2
ORS Dosing by Age and Severity
For Mild to Moderate Dehydration (Rehydration Phase):
- Infants and children: 50-100 mL/kg over 3-4 hours 1
- Adolescents and adults (≥30 kg): 2-4 L over 3-4 hours 1
- Alternative dosing after each stool:
ORS Composition:
Use reduced osmolarity ORS with total osmolarity <250 mmol/L (containing 65-70 mEq/L sodium and 75-90 mmol/L glucose), which is superior to standard WHO-ORS (311 mmol/L) 1, 3
Alternative Administration Routes
Nasogastric ORS should be considered when patients cannot tolerate oral intake or refuse to drink adequately, at a rate of 15 mL/kg body weight/hour for infants 1, 2
Intravenous Rehydration: When ORS Fails or Is Contraindicated
Indications for IV Therapy:
Switch to intravenous isotonic crystalloid (lactated Ringer's or normal saline) for: 1, 2, 3
- Severe dehydration with hemodynamic compromise
- Altered mental status or inability to protect airway
- Persistent vomiting preventing oral intake
- Evidence of ileus
- ORS failure after appropriate trial (occurs in ~4% of cases) 1
- Severe acidosis (associated with higher ORS failure rates) 4
IV Fluid Administration:
- Children, adolescents, and adults: Administer isotonic crystalloid boluses of up to 20 mL/kg body weight until pulse, perfusion, and mental status normalize 1
- Malnourished infants: Use smaller-volume, frequent boluses of 10 mL/kg due to reduced cardiac capacity 1
- Older adults: Consider subcutaneous dextrose infusions as an alternative to IV, which has similar efficacy and adverse effect rates 2
Maintenance and Ongoing Loss Replacement
Once rehydration is achieved:
- Administer maintenance fluids and replace ongoing losses with ORS until diarrhea and vomiting resolve 1, 2
- Infants <10 kg: 60-120 mL ORS per diarrheal stool or vomiting episode, up to ~500 mL/day 1
- Children >10 kg: 120-240 mL ORS per episode, up to ~1 L/day 1
- Adolescents and adults: Ad libitum, up to ~2 L/day 1
Feeding During Rehydration
Continue breast-feeding throughout the diarrheal episode in infants and children 1, 2
Resume age-appropriate usual diet during or immediately after rehydration is completed—early feeding (within 12 hours) is as safe and effective as delayed feeding 1, 2
For infants on formula in feeding centers, dilute milk with equal volume of clean water until diarrhea stops 1
Monitoring and Reassessment
- Reassess hydration status after 3-4 hours of treatment 2
- Monitor for signs of treatment failure: continued high stool output, persistent thirst, sunken eyes, fever, inability to keep down fluids 1, 2
- Track weight and clinical signs throughout therapy to assess adequacy of rehydration 1
- For severe cases: Monitor vital signs, mental status, and laboratory parameters as needed 2
Common Pitfalls to Avoid
Do not use IV therapy as first-line treatment for mild to moderate dehydration—ORT is equally effective, faster to initiate (19.9 vs 41.2 minutes), and results in fewer hospitalizations (30.6% vs 48.7%) 5
Avoid high-osmolarity solutions like soft drinks due to their high osmolality, which can worsen diarrhea 1
Do not withhold solid food for extended periods—the BRAT diet and dairy avoidance have limited supporting evidence 1
In diabetic patients with ketones, include carbohydrate intake (150-200g per day) to prevent starvation ketosis, and never omit insulin if insulin-dependent 3