Why is the Parkland formula (burn resuscitation formula) divided by 16 for every hourly calculation?

The Parkland Formula Division by 16 for Hourly Fluid Calculation

The Parkland formula divides the calculated 24-hour fluid requirement by 16 to determine hourly rates because half of the total volume is administered in the first 8 hours post-burn, and the remaining half is administered over the next 16 hours. 1, 2

Understanding the Parkland Formula

The Parkland formula is a widely used method for calculating initial fluid resuscitation requirements in burn patients:

• The formula calculates total fluid needs as 4 mL/kg/%TBSA for the first 24 hours post-burn 1
• This volume is not administered evenly over 24 hours, but follows a specific distribution pattern 1
• Half of the calculated volume is given in the first 8 hours post-burn 2
• The remaining half is administered over the next 16 hours 2

Mathematical Breakdown

When calculating the hourly rate for the first 8 hours:

• Total 24-hour volume = 4 mL/kg × %TBSA × weight(kg)
• First 8 hours receive 50% of this volume
• Hourly rate for first 8 hours = (Total volume × 0.5) ÷ 8

When calculating the hourly rate for the next 16 hours:

• Remaining 50% of volume is given over 16 hours
• Hourly rate for next 16 hours = (Total volume × 0.5) ÷ 16

Clinical Rationale

This distribution pattern reflects the pathophysiology of burn injury:

• The greatest fluid losses occur during the first 8 hours post-burn, requiring more aggressive resuscitation 3, 1
• Capillary permeability begins to normalize after 8-12 hours, reducing the rate of fluid extravasation 4
• The 16-hour divisor for the second half of resuscitation helps prevent fluid overload while maintaining adequate tissue perfusion 5

Importance of Adjustment Based on Clinical Response

While the formula provides an initial estimate, actual fluid requirements must be adjusted based on:

• Hourly urine output (target: 0.5-1 mL/kg/h in adults) 3, 1
• Clinical and hemodynamic parameters 3
• Avoiding both under-resuscitation and "fluid creep" (excessive fluid administration) 3, 5

Special Considerations

• Children have different fluid requirements due to higher body surface area-to-weight ratio 1, 2
• For burns >10% TBSA in children, a modified Parkland formula (3-4 mL/kg/%TBSA) is recommended 2
• Children typically require approximately 6 mL/kg/%TBSA in the first 48 hours 2

Common Pitfalls

• Relying solely on the formula without clinical adjustment can lead to inadequate or excessive fluid administration 3
• Calculation errors are common when using mental arithmetic or pen and paper methods 6
• Using nomograms or calculation aids can improve accuracy and reduce errors 6