Fluid Requirements for Moderate Dehydration
For moderate dehydration (6-9% fluid deficit), administer 100 mL/kg of oral rehydration solution (ORS) over 2-4 hours as first-line therapy. 1
Initial Rehydration Protocol
The standard approach for moderate dehydration involves supervised oral rehydration with specific volume targets:
- Administer ORS containing 50-90 mEq/L of sodium at 100 mL/kg over 2-4 hours 1
- Start with small volumes (one teaspoon) using a teaspoon, syringe, or medicine dropper, then gradually increase as tolerated 1
- For infants unable to drink but not in shock, nasogastric tube administration at 15 mL/kg/hour is an alternative 2
Critical reassessment point: After 2-4 hours, reassess hydration status; if still dehydrated, reestimate the fluid deficit and restart rehydration therapy 1
Replacement of Ongoing Losses
Beyond the initial rehydration volume, ongoing losses must be replaced concurrently:
- 10 mL/kg of ORS for each diarrheal stool 1
- 2 mL/kg of ORS for each episode of emesis 1
- For infants <10 kg: provide 60-120 mL ORS per diarrheal stool or vomiting episode, up to ~500 mL/day 1
Age-Specific Maintenance Volumes
For prevention of dehydration or after initial rehydration:
- Children <2 years: 50-100 mL of ORS after each stool 2
- Older children: 100-200 mL after each stool 2
- Adults: As much as they want, though those failing to respond promptly should be reassessed to exclude cholera 2
When to Switch to Intravenous Therapy
Intravenous fluids become necessary when:
- Progression to severe dehydration, shock, or altered mental status occurs 1
- ORS therapy fails (persistent vomiting or inability to tolerate oral intake) 1
- IV protocol: 60-100 mL/kg of 0.9% saline or lactated Ringer's in the first 2-4 hours to restore circulation 3
- Rapid IV rehydration at 20 mL/kg/hour for 2 hours has shown 83% success in moderate dehydration 4
Common Pitfalls to Avoid
Underutilization of ORT: Research demonstrates that ORT is as effective as IV therapy for moderate dehydration, with 72% of moderately dehydrated children successfully managed without hospitalization 5. However, many physicians still default to IV therapy unnecessarily 5.
Inadequate ORS tolerance testing: Children who tolerate at least 25 mL/kg of ORS during initial observation have significantly better outcomes with home oral rehydration compared to those tolerating only 11 mL/kg 6. This threshold can guide discharge decisions.
Severe acidosis indicator: Serum bicarbonate ≤13 mEq/L predicts ORT failure; most children with bicarbonate >13 mEq/L tolerate oral fluids after brief IV rehydration, while those ≤13 mEq/L typically require prolonged IV therapy 7.
Feeding During Rehydration
- Breastfed infants: Continue nursing on demand throughout illness 1
- Bottle-fed infants: Use full-strength, lactose-free, or lactose-reduced formulas immediately upon rehydration 1
- Children >4-6 months: Offer age-appropriate foods every 3-4 hours as tolerated 2
Monitoring Response
Regularly assess clinical signs including: