What are the current guidelines for pediatric oral rehydration therapy, including solution composition and weight‑based dosing for mild, moderate, and severe dehydration?

Oral Rehydration Therapy in Pediatric Patients

Use low-osmolarity oral rehydration solution (ORS) containing 75-90 mEq/L sodium as first-line therapy for all children with mild-to-moderate dehydration from acute diarrhea, regardless of cause. 1

ORS Solution Composition

The recommended formulation contains:

• Sodium: 75-90 mEq/L for active rehydration 1
• Potassium: ~20 mEq/L 1
• Glucose: 75-111 mmol/L 1
• Total osmolarity: <250 mOsm/L (low-osmolarity formulation) 1

Commercially available products meeting these specifications include Pedialyte, CeraLyte, and Enfalac Lytren. 1 Note that standard Pedialyte (45 mEq/L sodium) and Ricelyte (50 mEq/L sodium) contain lower sodium concentrations and are primarily designed for maintenance rather than active rehydration, though they can be used for rehydration when higher-sodium solutions are unavailable. 1

Weight-Based Dosing by Dehydration Severity

Mild Dehydration (3-5% fluid deficit)

• Administer 50 mL/kg of ORS over 2-4 hours 1
• For a 10 kg child: 500 mL over 2-4 hours
• For a 20 kg child: 1000 mL over 2-4 hours

Moderate Dehydration (6-9% fluid deficit)

• Administer 100 mL/kg of ORS over 2-4 hours 1
• For a 10 kg child: 1000 mL over 2-4 hours
• For a 20 kg child: 2000 mL over 2-4 hours

Severe Dehydration (≥10% fluid deficit, shock, altered mental status)

• Begin immediate intravenous rehydration with 20 mL/kg boluses of lactated Ringer's or normal saline until pulse, perfusion, and mental status normalize 1
• Once the patient awakens and has no aspiration risk or ileus, transition to ORS to complete rehydration 1

No Clinical Dehydration (Prevention)

• Skip rehydration phase and proceed directly to maintenance therapy 1

Ongoing Loss Replacement

During both rehydration and maintenance phases, replace ongoing losses:

• 10 mL/kg for each watery or loose stool 1
• 2 mL/kg for each vomiting episode 1

Alternatively, if stool can be measured accurately, give 1 mL of ORS for each gram of diarrheal stool. 1

Administration Technique

For children who are vomiting:

• Give small aliquots of 5-10 mL every 1-2 minutes using a teaspoon, syringe, or medicine dropper 1
• Gradually increase volume as tolerated 1
• This method successfully rehydrates >90% of vomiting children 2

If oral intake fails but the child is not in shock:

• Administer ORS via nasogastric tube at 15 mL/kg/hour 1

Maintenance Phase After Rehydration

Once rehydration is complete (reassess after 2-4 hours):

• Continue breastfeeding throughout the illness without interruption 1
• Resume full-strength formula immediately—do not dilute 1
• Offer age-appropriate normal diet every 3-4 hours 1
• Use maintenance ORS (40-60 mEq/L sodium) or continue rehydration ORS supplemented with low-sodium fluids (breast milk, formula, water) to prevent sodium overload 1

The outdated practice of "gut rest" or formula dilution offers no benefit and may worsen nutritional outcomes. 1

Critical Contraindications

Absolute contraindications to ORS:

• Intestinal ileus (absent bowel sounds) 2
• Altered mental status or inability to protect airway 1
• Shock or severe dehydration requiring immediate IV access 1

Fluids to Avoid

Never use apple juice, sports drinks (Gatorade), soft drinks, or other commercial beverages for rehydration. 1 These have inappropriate electrolyte composition and excessive osmolarity that can worsen diarrhea. 1

When to Escalate to Intravenous Therapy

Switch to IV fluids if:

• Stool output exceeds 10 mL/kg/hour 1
• Persistent dehydration signs after 3-4 hours of adequate ORS therapy 1
• Development of severe lethargy, shock, or altered mental status 1
• Paralytic ileus develops 1
• Intractable vomiting prevents oral/NG intake 1

The failure rate of ORS is approximately 4% in properly selected patients. 1

Common Pitfalls

• Mixing ORS packets incorrectly: When using powder packets, provide detailed written and oral instructions to ensure proper dilution. 1 Incorrect mixing creates solutions that are too concentrated or too diluted.

• Using maintenance solutions for active rehydration: While Pedialyte (45 mEq/L sodium) can be used when alternatives are inappropriate fluids or IV therapy, solutions with 75-90 mEq/L sodium are preferable for rehydration, especially when purging rate exceeds 10 mL/kg/hour. 1

• Delaying feeding: Resume normal diet immediately after rehydration is achieved; do not wait for diarrhea to resolve. 1

• Hypernatremia concerns: Low-osmolarity ORS is safe in both hypernatremia and hyponatremia (except when edema is present). 1 The 75-90 mEq/L sodium concentration corrects hypernatremia more slowly, protecting against seizures during treatment. 1

Physiologic Rationale

The sodium-glucose cotransport mechanism in the intestinal brush border remains intact during diarrhea of any etiology, enabling ORS to promote water and electrolyte absorption regardless of the underlying cause. 1 This mechanism has saved millions of lives globally and is credited as one of the most important medical advances of the 20th century. 1