What is the role of Oral Rehydration Solution (ORS) in treating dehydration?

Role of Oral Rehydration Solution (ORS) in Rehydration

ORS is the first-line therapy for mild to moderate dehydration in all age groups with acute diarrhea, working through coupled sodium-glucose transport to enhance water absorption across the intestinal brush border, and should be used before resorting to intravenous fluids except in specific contraindications. 1

Primary Mechanism and Efficacy

ORS functions through the coupled transport of sodium and glucose across the intestinal brush border, enabling enhanced water absorption even during active diarrhea 1. This cyclic AMP-independent process allows effective rehydration regardless of the etiology of diarrhea 2. The therapy has been the cornerstone of diarrheal disease management for over 40 years and is the primary reason for substantial reduction in morbidity and mortality from diarrhea in children globally 2, 3.

Specific Indications

ORS is indicated as first-line therapy for:

• Mild to moderate dehydration in infants, children, and adults with acute diarrhea from any cause 1
• Maintenance therapy after rehydration until diarrhea and vomiting resolve 1
• Prevention of dehydration when administered early at home 4

Dosing Algorithm

For rehydration phase:

• Mild dehydration: 50-100 mL/kg over 3-4 hours 1
• Moderate dehydration: 100-200 mL/kg over 3-4 hours 1

For maintenance phase (after each loose stool):

• Children under 2 years: 50-100 mL 1
• Older children: 100-200 mL 1

Administration Technique

Critical pitfall to avoid: Do not allow thirsty children to drink large volumes ad libitum from a cup or bottle, as this commonly leads to vomiting and perceived ORS failure 4. Instead, administer small volumes (5-10 mL) every 1-2 minutes via spoon, syringe, or cup, with gradual increases 4. This technique successfully rehydrates over 90% of patients with concomitant vomiting 4.

For patients unable to tolerate oral intake, nasogastric administration via continuous slow infusion can be effective 4, 1. Research demonstrates that children tolerating at least 25 mL/kg of ORS during an initial tolerance test have an 80% success rate with home oral rehydration therapy 5.

Absolute Contraindications

ORS should NOT be used in:

• Severe dehydration with shock or near-shock (use IV fluids initially) 4, 1
• Altered mental status 1, 3
• Intestinal ileus (wait until bowel sounds return) 4, 1
• True glucose malabsorption (approximately 1% incidence, diagnosed when stool output dramatically increases with ORS and immediately decreases with IV therapy) 4

Relative Limitations Requiring Caution

Bloody diarrhea (dysentery): ORS alone is insufficient; patients require immediate medical evaluation for antimicrobial therapy 4

High stool output (>10 mL/kg/hour): Higher sodium concentration solutions (75-90 mEq/L) are recommended rather than standard commercial preparations 4, 6. However, no patient should be denied ORT simply because of high purging rate, as most respond with adequate replacement 4.

Solution Composition Considerations

The WHO recommends low-osmolarity ORS with sodium 65-70 mEq/L and glucose 75-90 mmol/L for optimal absorption 6. Commercial preparations like Pedialyte and Ricelyte contain lower sodium (45-50 mEq/L) and are designed primarily for maintenance rather than rehydration 4, 6. While these lower-sodium solutions can be used for rehydration when the alternative is physiologically inappropriate liquids or IV fluids, higher sodium solutions (75-90 mEq/L) are preferable for actual rehydration, particularly with severe purging 4, 6.

Advantages Over IV Therapy

ORS is superior to IV fluids because it:

• Enables earlier treatment and prevention of dehydration at home 4
• Is safer and more physiologic than IV administration 4
• Avoids risks of phlebitis and IV infiltrates 4
• Is more efficacious when combined with early feeding 4
• Promotes active parental involvement in care 4

Integration with Nutritional Therapy

ORS must be combined with appropriate dietary therapy, as acute diarrhea endangers nutritional status through anorexia, malabsorption, and excess losses 4. Early feeding reduces severity, duration, and nutritional consequences of diarrhea 4. The most crucial aspect of home management is administering increased volumes of appropriate fluids while maintaining adequate caloric intake 4.

Common Pitfalls to Avoid

• Never use popular beverages like apple juice, Gatorade, soft drinks, or chicken broth for rehydration, as they have inappropriate electrolyte content 6, 7
• Avoid antimotility drugs in children under 18 years with acute diarrhea 1
• Do not use medications, inappropriate home remedies, or withhold food 4
• Recognize that presence of reducing substances in stool alone does not indicate ORS failure; this is common in diarrhea and does not necessitate switching to IV therapy 4