What are the recommended intravenous fluid volumes in milliliters per kilogram for a child without cardiac, renal, or severe electrolyte disorders presenting with mild, moderate, and severe dehydration?

IV Fluid Volumes for Pediatric Dehydration

For children without cardiac, renal, or severe electrolyte disorders, administer 50 mL/kg over 2-4 hours for mild dehydration, 100 mL/kg over 2-4 hours for moderate dehydration, and 20 mL/kg boluses (up to 60 mL/kg in the first hour) for severe dehydration using isotonic crystalloid solutions. 1, 2

Mild Dehydration (3-5% Fluid Deficit)

• Volume: 50 mL/kg over 2-4 hours using oral rehydration solution containing 50-90 mEq/L sodium 1
• If IV access is necessary, isotonic crystalloid (0.9% saline or lactated Ringer's) should be used at the same volume 2
• Reassess hydration status after 2-4 hours; if still dehydrated, reestimate deficit and restart rehydration 1
• Clinical signs include normal mental status, slightly decreased urine output, slightly dry mucous membranes, and normal capillary refill 1

Moderate Dehydration (6-9% Fluid Deficit)

• Volume: 100 mL/kg over 2-4 hours using the same fluid composition as mild dehydration 1
• Administer small volumes initially (one teaspoon) and gradually increase as tolerated 1
• Children commonly require 40-60 mL/kg in the first hour when presenting with moderate dehydration 1
• Monitor for signs of fluid overload including hepatomegaly, rales, increased work of breathing, or gallop rhythm 1

Severe Dehydration (≥10% Fluid Deficit, Shock)

• Initial bolus: 20 mL/kg of isotonic crystalloid (0.9% saline or Ringer's lactate) administered rapidly by push or pressure bag 1, 2
• Repeat 20 mL/kg boluses up to 60 mL/kg total in the first hour, with mandatory reassessment after each bolus 1, 2
• Children with septic shock may require up to 200 mL/kg in the first hour, though this exceeds typical dehydration needs 1
• Clinical signs include severe lethargy/altered consciousness, prolonged skin tenting (>2 seconds), cool extremities, decreased capillary refill, and rapid deep breathing 1

Critical Reassessment Points After Each Bolus

Evaluate for positive response including: 1, 2

• ≥10% increase in systolic/mean arterial blood pressure
• ≥10% reduction in heart rate
• Improvement in mental status and peripheral perfusion
• Capillary refill ≤2 seconds
• Urine output >1 mL/kg/hour

Fluid Type Selection

Use isotonic crystalloid (0.9% saline or lactated Ringer's) for all IV rehydration in children. 1, 2, 3 The American College of Critical Care Medicine specifically recommends against hypotonic solutions due to significant risk of iatrogenic hyponatremia and potentially fatal hyponatremic encephalopathy. 2, 4

Ongoing Loss Replacement

During rehydration, replace continued losses: 1

• 10 mL/kg for each watery/loose stool
• 2 mL/kg for each vomiting episode
• If losses can be measured accurately, give 1 mL of ORS for each gram of diarrheal stool 1

Signs to Stop Fluid Administration

Immediately cease fluid administration if any of the following develop: 1, 2

• Pulmonary rales/crackles
• Hepatomegaly
• Progressive peripheral edema
• Increased work of breathing
• Deterioration of oxygenation
• Gallop rhythm

When these signs appear, initiate inotropic support rather than continuing fluid resuscitation. 1

Common Pitfalls to Avoid

• Do not rely on blood pressure alone in children, as hypotension is a late finding due to compensatory vasoconstriction and tachycardia 1
• Do not use hypotonic fluids (such as 0.45% saline or 0.2% saline) for acute rehydration, as they significantly increase hyponatremia risk 2, 4
• Do not delay treatment waiting for laboratory results in severe dehydration; begin boluses immediately based on clinical assessment 1
• Do not exceed 60 mL/kg in the first hour without reassessing for fluid overload, as higher volumes are associated with worse outcomes in most conditions 2

Transition to Maintenance

Once clinical hydration is attained (normal perfusion, capillary refill ≤2 seconds, adequate urine output, normal mental status), transition to maintenance fluids using the Holliday-Segar formula: 100 mL/kg/day for first 10 kg + 50 mL/kg/day for next 10 kg + 25 mL/kg/day for each kg above 20 kg. 2, 5