In an adult without cardiac, renal, or severe electrolyte disease, what are the recommended intravenous crystalloid fluid volumes in milliliters per kilogram for mild, moderate, and severe dehydration?

IV Fluid Volumes for Dehydration in Adults

For adults without cardiac or renal disease, administer isotonic saline (0.9% NaCl) at 15-20 ml/kg/hr for the first hour for moderate to severe dehydration, then reduce to 4-14 ml/kg/hr for subsequent hours until rehydration is complete. 1, 2

Severity-Based Fluid Resuscitation Protocol

Severe Dehydration

• Initial bolus: 15-20 ml/kg/hr of isotonic saline (0.9% NaCl) for the first hour 1, 2
• Subsequent hours: Continue at 4-14 ml/kg/hr until deficits are corrected 2
• Total expected deficit: Approximately 6 liters (100 ml/kg) in severe cases 2
• Goal: Correct estimated deficits within 24 hours 2

Moderate Dehydration

• Initial approach: 10-20 ml/kg bolus over the first hour 3
• Maintenance rate: 1.5-3 ml/kg/hr for ongoing replacement 3
• Alternative protocol: 5-10 ml/kg in the first 5 minutes, followed by slower infusion 3

Mild Dehydration

• Conservative approach: 10 ml/kg bolus followed by 1.5 ml/kg/hr 3
• Consider oral rehydration as first-line when feasible, as IV offers minimal advantage in mild cases 4

Critical Clinical Considerations

Fluid Selection

• Use isotonic saline (0.9% NaCl) initially for all moderate to severe dehydration 1, 2
• Isotonic saline prevents rapid osmotic shifts that could precipitate cerebral edema 1
• Avoid hypotonic fluids initially in severely dehydrated patients due to cerebral edema risk 1

Monitoring Parameters

• Limit osmolality change to <3 mOsm/kg/hr to prevent neurological complications 1, 2
• Monitor hemodynamics, fluid input/output, and clinical examination continuously 2
• Assess for signs of fluid overload, particularly in patients with borderline cardiac or renal function 2

Volume Requirements by Context

• Anaphylaxis: 1-2 liters rapidly at 5-10 ml/kg in first 5 minutes; up to 7 liters of crystalloid may be necessary due to massive capillary leak (50% of intravascular volume can shift to extravascular space within 10 minutes) 3
• Standard dehydration: Average total deficit of 6 liters requires systematic replacement over 24 hours 2

Common Pitfalls to Avoid

• Aggressive fluid protocols (>3 ml/kg/hr maintenance) increase complications including sepsis and fluid overload without improving clinical outcomes in conditions like acute pancreatitis 3
• Excessive maintenance fluids after initial resuscitation can cause peripheral, pulmonary, and splanchnic edema, potentially resulting in ileus 5
• Failure to reduce rate after initial resuscitation leads to positive fluid balance; most patients require only 2-2.5 liters/day for maintenance after volume repletion 5
• Using lactated Ringer's may contribute to metabolic acidosis; normal saline is preferred for initial resuscitation 3

Practical Algorithm Summary

1. First hour: 15-20 ml/kg of 0.9% NaCl (approximately 1-1.5 liters for 70 kg adult) 1, 2
2. Subsequent hours: Reduce to 4-14 ml/kg/hr based on clinical response 2
3. Reassess frequently: Monitor vital signs, urine output, and clinical examination 2
4. Transition to maintenance: Once resuscitated, reduce to 2-2.5 liters/day to avoid overload 5