What are the best fluids to treat dehydration?

Best Fluids for Dehydration

Reduced osmolarity oral rehydration solution (ORS) containing 50-90 mEq/L sodium is the first-line treatment for mild to moderate dehydration in all age groups, while isotonic intravenous fluids (lactated Ringer's or normal saline) are required for severe dehydration with shock or altered mental status. 1, 2

Treatment Algorithm Based on Dehydration Severity

Mild Dehydration (3-5% fluid deficit)

• Administer ORS containing 50-90 mEq/L sodium at 50 mL/kg over 2-4 hours 1, 2
• Start with small volumes (one teaspoon) using a spoon, syringe, or medicine dropper, then gradually increase as tolerated 1
• Reassess hydration status after 2-4 hours; if still dehydrated, reestimate deficit and restart rehydration 1
• Replace ongoing losses with 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 1, 3

Moderate Dehydration (6-9% fluid deficit)

• Use the same ORS formulation but increase volume to 100 mL/kg over 2-4 hours 1, 2
• Consider nasogastric administration if the patient cannot tolerate oral intake but has normal mental status 1
• Continue replacing ongoing losses as described above 1

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

• This is a medical emergency requiring immediate IV rehydration 1, 2
• Administer 20 mL/kg boluses of lactated Ringer's solution or normal saline until pulse, perfusion, and mental status normalize 1, 2
• May require two IV lines or alternate access sites (venous cutdown, femoral vein, intraosseous infusion) 1
• Once consciousness returns and patient is stable, transition to ORS for remaining deficit replacement 1, 2

Specific ORS Formulations

Recommended Commercial Products

• Acceptable products include Pedialyte (45 mEq/L sodium), CeraLyte, and Enfalyte/Infalyte (50 mEq/L sodium) 1, 2
• The WHO reduced osmolarity ORS (total osmolarity <250 mmol/L) is the gold standard 1, 2, 4
• Solutions with 75-90 mEq/L sodium are preferable for rehydration, though lower sodium solutions (40-60 mEq/L) can be used when the alternative is IV fluids 1

When Higher Sodium Solutions Are Used

• If using ORS with >60 mEq/L sodium for maintenance, provide additional low-sodium fluids (breast milk, formula, or water) to prevent sodium overload 1
• When purging rate exceeds 10 mL/kg/hour, solutions with 75-90 mEq/L sodium are specifically recommended 1

Special Population Considerations

Infants and Young Children

• Breastfed infants must continue nursing on demand throughout the illness 1, 2
• Bottle-fed infants should receive full-strength, lactose-free or lactose-reduced formulas immediately upon rehydration 1, 2, 3
• Resume age-appropriate diet during or immediately after rehydration is complete 1, 2

Older Adults with Low-Intake Dehydration

• For older adults with serum osmolality >300 mOsm/kg who appear well, encourage increased intake of preferred beverages (tea, coffee, juice, water)—NOT oral rehydration therapy or sports drinks 1
• For older adults who appear unwell, offer subcutaneous or intravenous hypotonic fluids in parallel with encouraging oral intake 1
• Subcutaneous dextrose infusions (half-normal saline-glucose 5% or two-thirds 5% glucose and one-third normal saline) are effective alternatives to IV with similar adverse effect rates 1

Critical Contraindications and Pitfalls

When NOT to Use ORS

• Avoid ORS in patients with altered mental status, inability to tolerate oral/nasogastric intake, paralytic ileus, or severe dehydration with shock 1, 2, 4
• Switch to IV fluids immediately if ORS therapy fails 1, 2

Fluids to AVOID

• Do not use soft drinks, sports drinks (except for exercise-related dehydration), fruit juices alone, or chicken broth for rehydration 1, 5
• These have inappropriate osmolality and electrolyte composition for treating dehydration from diarrhea 1, 5
• Oral rehydration therapy formulated for diarrhea is NOT indicated for simple low-intake dehydration in older adults 1

Common Errors to Avoid

• Do not allow ad libitum drinking in vomiting patients—administer small volumes every 1-2 minutes via spoon or syringe 3
• Do not practice "resting the bowel" through prolonged fasting 1, 2
• Do not use anti-diarrheal or antimotility agents as substitutes for fluid therapy 1

Monitoring During Treatment

Reassessment Parameters

• Monitor pulse, perfusion, mental status, urine output, and body weight 1, 2
• In severe cases with renal or cardiac compromise, monitor serum osmolality and perform frequent cardiac, renal, and mental status assessments to avoid fluid overload 2
• The induced change in serum osmolality should not exceed 3 mOsm/kg/hour during fluid replacement 2

Evidence Supporting ORS Over IV Therapy

• A meta-analysis of 17 RCTs involving 1,811 pediatric patients demonstrated no clinically important differences between ORS and IV therapy in rehydration success, weight gain, electrolyte abnormalities, or diarrhea duration, supporting ORS as the safer first-line approach 2
• Reduced osmolarity ORS decreases the need for supplemental IV fluids by 24.5% compared to standard ORS formulations 6