4-2-1 Rule Calculation for 31kg Patient
For a 31kg patient, the 4-2-1 rule calculates an hourly maintenance IV fluid rate of 71 mL/hour, which equals approximately 1,704 mL per 24 hours—well below the 1000mL reference point in your question.
Calculation Breakdown
The 4-2-1 rule (also called Holliday-Segar formula) calculates maintenance fluid requirements based on weight 1, 2:
- First 10 kg: 4 mL/kg/hour = 40 mL/hour 2
- Second 10 kg (11-20 kg): 2 mL/kg/hour = 20 mL/hour 2
- Remaining 11 kg (21-31 kg): 1 mL/kg/hour = 11 mL/hour 2
Total hourly rate = 40 + 20 + 11 = 71 mL/hour
Total 24-hour maintenance = 71 mL/hour × 24 hours = 1,704 mL/day
Clinical Context
When This Formula Applies
- This calculation provides baseline maintenance fluid requirements for pediatric patients, particularly useful in burn management where it's added to resuscitation formulas 1
- For children with burns >10% TBSA, calculate daily basal fluid intake using the 4-2-1 rule, then add the modified Parkland formula requirements (3-4 mL/kg/%TBSA) 1
Important Caveats
- This is maintenance only, not resuscitation fluid 1, 2
- For acute resuscitation in pediatric shock, initial bolus therapy is 10-20 mL/kg of isotonic saline over 15 minutes, not exceeding 50 mL/kg in the first 4 hours 1, 2
- The 4-2-1 rule does not account for ongoing losses or deficit replacement 2
- In septic shock, children may require up to 30 mL/kg in the first hour for resuscitation, separate from maintenance 1
Relationship to 1000mL
If your question relates to whether 1000mL is appropriate for this patient:
- 1000mL represents approximately 14 hours of maintenance fluid (1000 ÷ 71 = 14.1 hours)
- As a single bolus, 1000mL would equal 32 mL/kg, which exceeds recommended initial resuscitation volumes of 10-20 mL/kg 1, 2
- For maintenance infusion, 1000mL should be administered over approximately 14 hours, not as a rapid bolus